## Findings of the Moon→Mars Science Linkage Science Steering Group

October 24, 2004

This report was prepared by the Moon-Mars Science Linkages Science
Steering Group

> Charles Shearer, University of New Mexico, co-Chair
>
> David Beaty, Mars Program Office (JPL), co-Chair
>
> Ariel D. Anbar, Arizona State University
>
> Bruce Banerdt, JPL
>
> Don Bogard, JSC
>
> Bruce A. Campbell, Smithsonian CEPS
>
> Michael Duke, Colorado School of Mines
>
> Lisa Gaddis, USGS, Flagstaff
>
> Brad Jolliff, Washington University
>
> Rachel C.F. Lentz, University of Tennessee
>
> David McKay, JSC
>
> Greg Neumann, GSFC/MIT
>
> Dimitri Papanastassiou, JPL
>
> Roger Phillips, Washington University
>
> Jeff Plescia, JHU APL
>
> Mini Wadhwa, Field Museum, Chicago

# **This report has been approved for public release by JPL Document Review Services (CL#04-2703), and may be freely circulated. Recommended bibliographic** **citation:**

Shearer, C., Beaty, D.W., Anbar, A.D., Banerdt, B., Bogard, D.,
Campbell, B.A., Duke, M., Gaddis, L., Jolliff, B., Lentz, R.C.F., McKay,
D., Neumann, G., Papanastassiou, D., Phillips, R., Plescia, J., and
Wadhwa, M. (2004). Findings of the Moon→Mars Science Linkage Science
Steering Group. Unpublished white paper, 29 p, posted October, 2004 by
the Mars Exploration Program Analysis Group (MEPAG) at
http://mepag/reports/index.html.

or

Shearer, C. and 15 co-authors, (2004). Findings of the Moon→Mars Science
Linkage Science Steering Group. Unpublished white paper, 29 p, posted
October, 2004 by the Mars Exploration Program Analysis Group (MEPAG) at
http://mepag/reports/index.html.

**PREAMBLE**

**Introduction**

The new solar system exploration initiative proposed by the President of
the United States refocuses NASA by establishing an exciting long-term
vision that integrates robotic and human exploration programs around
focused science goals and milestones. Within this new direction of solar
system exploration, the scientific linkages between Moon and Mars have
become increasingly important. Owing to the proximity of the Moon to
Earth, there are important technological and scientific concepts that
could be developed on the Moon that will provide valuable insights into
both the origin and evolution of the terrestrial planets and be
feed-forward to the scientific exploration of Mars. This document
identifies important lunar scientific and technology goals and evaluates
them with regard to how they could provide valuable insights for Mars.
This evaluation is done within the context of the Mars Exploration
Program as defined by the *MEPAG Scientific Goals, Objectives,
Investigations, and Priorities,2004* document, the vision of Moon
science developed by the Lunar Exploration Science Working Group
(LExSWG), and solar system exploration programs described in the *Solar
System Exploration Roadmap* (NASA Office of Space Sciences) and *New
Frontiers in the Solar System: An Integrated Exploration Strategy* (NAS
National Research Council). The main thrust of this document is to
establish lunar-science priorities within the context of Mars
exploration. On the basis of their relevance to important solar system
problems, a set of lunar priorities were a consequence of this exercise
and we anticipate that further discussion along these lines will
continue in a different forum.

The Moon→Mars Science Linkage Science Steering Group (MMSSG) was formed
within the oversight of the Mars Exploration Program Analysis Group
(MEPAG) in response to a request from NASA HQ to develop an analysis of
the science-based activities on the lunar surface that would benefit the
scientific exploration of Mars. The steering group consisted of 16
members with scientific backgrounds in varies aspects of lunar and
martian science. The science steering group met through biweekly
teleconferences from mid-April 2004 to the end of June 2004. The
steering group and subcommittees communicated by e-mail throughout the
process. The committee identified important lunar problems that remained
to be addressed or reappraised. The committee then evaluated these
important lunar science themes within the context of the scientific
exploration of Mars. The committee also identified important
technological demonstrations that would be instrumental to the
scientific exploration of the Moon and Mars, and important for eventual
manned occupancy of both planetary bodies. Priority criteria were
established for lunar science by subcommittees and agreed to by the full
steering group. One set of priority criteria was set within the context
of lunar exploration and the second was set within the context of MEPAG
priorities. Using these established criteria, lunar science themes and
their importance to Mars exploration were prioritized. Both the
lunar-science priorities on their own and the lunar-science priorities
within the framework of Mars are presented in this document. In
addition, the science steering group developed specific case examples of
an activity on the Moon and then characterized them in terms of
high-level functional requirements, with examples of how the activity
would specifically benefit Mars. A draft report was circulated to the
MEPAG executive committee and discussed in detail during the June
30-July 2, 2004 MEPAG meeting in Monrovia, California. Insights derived
from these discussions were incorporated into this final report.

[Relative Prioritization]{.underline}. In summary, the Moon→Mars Science
Linkage Science Steering Group (MMSSG) has identified 20 science-based
activities that would be of clearly defined benefit to the already
prioritized scientific exploration of Mars. These activities fall into
two overall groups, with 10 elements each: 1) science investigations,
and 2) demonstrations of science-relevant engineering or technological
approaches. The relative priority of each list of 10 elements was
assessed using pre-established criteria, and in a general way, the
comparative priority of the two lists can be determined. However, there
was **no** attempt to determine the priority of the ensemble set of the
derived 20 possible lunar activities relative to any of the following:

-   Options for advancing martian science by carrying out similar
    investigations directly at Mars.

-   Options for demonstrating technology or infrastructure at Earth,
    rather than at the Moon.

-   Options for advancing lunar science through alternate investigations
    that do not have a linkage to Mars.

The MMSSG is aware that judging scientific priority in broader context
such as this commonly involves political and programmatic factors that
are outside the scope of science-based prioritization, such as budget,
NASA's strategic directives, the status of existing engineering
programs, and other factors. However, within the scope that MMSSG has
operated, the priorities developed may provide a useful framework for
NASA decision-making.

**Assumptions for this Study**

This analysis is based on the following lines of thought:

-   Evaluate how MEPAG's scientific objectives for Mars (and their
    derivative investigations and measurements) could be enhanced by a
    first application on the Moon.

-   Determine whether demonstrations of engineering capability at the
    Moon could have significant feed forward to the Mars scientific
    exploration program.

-   Determine whether any of the primary scientific exploration goals
    and objectives for the Moon are linked to the goals and objectives
    for Mars.

The analysis included both an assessment of the [potential]{.underline}
ways in which the scientific objectives for the exploration of Mars can
be advanced, and their priorities. The full charter of the MMSSG is
contained in Appendix I. Several assumptions were made concerning the
identification and prioritization of lunar science within the context of
the exploration of Mars. We first assumed scientific priorities for the
exploration of Mars that are described in the MEPAG Goals document:

> Scientific Goals, Objectives, Investigations, and Priorities: 2003.
> Unpublished document
> (<http://mepag.jpl.nasa.gov/reports/MEPAG_goals-3-15-04-FINAL.doc>)

Lunar science objectives were partially prioritized based on the most
recent consensus-based description of lunar-science goals, objectives,
and investigations that was developed by the Lunar Exploration Science
Working Group (LExSWG). This information is available in the following
reports:

> Planetary Science Strategy for the Moon, Lunar Exploration Science
> Working Group, July 1992, JSC document JSC-25920, 26 pp.
>
> Lunar Surface Exploration Strategy, Lunar Exploration Science Working
> Group (LExSWG), Final Report, February, 1995, 50 pp.

We also assumed a Lunar Reconnaissance Orbiter (LRO) mission to the Moon
in 2008, a robotic landed mission by 2010, and a TBD schedule of robotic
lunar missions until a first human return to the lunar surface in 2020.
This SSG was asked to focus its effort on martian and lunar surface
science, rather than orbital science.

This document is structured to first present an overview of the Moon as
a unique vantage point for solar system exploration and general themes
for Moon**→**Mars science linkages. This is followed by an outline of
criteria used for prioritization of science investigations. Individual
science investigations are explored with regards to linkage between Moon
and Mars, relevance to lunar and martian science, and measurements that
could be made on the lunar surface. These investigations are then
prioritized with regards to their relevance to the exploration of Mars.

**Moon→Mars Science Linkages**

**Early Planetary Evolution and Planetary Structure**

The Moon has been and will continue to be the scientific foundation for
our understanding of the early evolution of the terrestrial planets. The
detailed geologic record of these early events has long since vanished
from the Earth and has been at least partially erased from Mars. The
Moon contains the remnants of one of the basic mechanisms of early
planetary differentiation: magma ocean. These remnants are in the form
of a primary planetary crust and subsequent crustal additions that were
products of melting of magma-ocean products in the lunar mantle. The
idea of a magma ocean has been extended by many investigators to the
Earth, Mars, and even to asteroids (Benz and Cameron, 1990). Isotopic
studies of basalts from both the Moon and Mars suggest a similarity in
their early differentiation in that that their mantle sources formed
very early and rapidly. Both bodies also exhibit planetary asymmetry
that may reflect processes that functioned during early differentiation.
Clearly, the differences in size and formation between the Moon and Mars
have affected the style of differentiation and early magmatism. However,
the Moon provides a valuable and nearly complete end-member model for a
style of planetary differentiation and early planetary magmatism.

Four Moon-Mars themes were identified to fit within this subject:

-   *Composition and Structure of Planetary Interiors*

-   *Early Planetary Differentiation*

-   *Planetary Thermal and Magmatic Evolution*

-   *Planetary Asymmetry*

**Evolution of Planetary Surface**

Some surface modification processes will be very similar for the Moon
and Mars, and others will differ due to the presence of fluid erosion
and chemical weathering on Mars. The Moon retains the history of the
early impact environment of the inner solar system, at the time when
life may have first arisen on the Earth and perhaps Mars. The
bombardment history of the Moon and Mars may be similar, and this
history will help to construct timelines for erosional, depositional,
and volcanic features on Mars. It will also provide valuable insights
into the potential habitability of the early surface of Mars.

Three Moon-Mars themes were identified to fit within this topic:

-   *Impactor Flux versus Time*

-   *Interpreting Geologic Environments*

-   *Structure and Composition of Planetary Regoliths*

**Record of Volatile Evolution and Behavior**

This is perhaps the most important overall theme for the major stated
goals for the Mars Exploration Program of life, water, and climate.
Among these three themes, the origin and history of endogenic volatiles
will be the most important theme for Mars. Because the Moon is
volatile-poor and has no atmosphere, lunar science has only little to
contribute to the origin and history of planetary volatiles. As Mars and
the Moon are at nearly opposite ends of the volatile spectrum for rocky
planets, most of the volatile science studies to be conducted on Mars
are not possible on the Moon. There are several special cases were the
study of lunar volatiles may be relevant to Mars. "Energetic particles",
whose composition and interaction have been well studied on the Moon and
whose study on Mars will probably be limited to determination of
near-surface exposure histories. The characterization and exploitation
of possible water-ice at the lunar poles may be important as a resource
for human exploration. In addition, it provides insight into the
transport of volatiles on airless planetary bodies. Another special case
is the nature of lunar endogenic volatiles that provide insights into
the nature of volatile reservoirs in early planetary mantles.

Three Moon-Mars themes were identified to fit within this topic:

-   *Energetic Particle History*

-   *Origin and History of Endogenic Volatiles*

-   *Origin and History of Exogenous Volatiles*

**Human Resource Issues**

Most recent architectures for the human exploration of Mars have
included the principle of using martian resources to produce propellant
for the return trip. A long-term human outpost on Mars and on the Moon
can also benefit from applying local resources to outpost support in
areas that include construction of facilities to providing reservoirs of
important consumables (water, oxygen, nitrogen, etc.) from local
resources. The Moon is viewed as a place where the basic principles can
be tested for the first time. Although the lunar and martian
environments differ in detail, there are important similarities. For
example, it may prove desirable to extract water from hydrated minerals
in the Martian regolith, which will require processes similar to those
that might be used to extract hydrogen or water ice from the lunar
regolith. Many subsystems such as electrolysis cells, gas liquefaction
systems, life support, operational autonomy, surface mobility, and
storage and handling systems, will be common for the Moon and Mars. In
addition, the Moon can be an important location for the study of the
long-term effects on humans and human activity in less than 1-g
environments. This understanding is critical to the safety of the first
astronauts who will spend extensive time traveling to and exploring the
surface of Mars.

Lunar resources are most useful on the Moon, but if propellants are
available on the Moon, may also be transported into space. Thus, lunar
propellant production might also benefit Mars exploration, for which
very large amounts of propellant are required in space, and which bears
a transportation cost that might be somewhat mitigated by the
availability of supplies on the Moon. Any long-term utilization of the
lunar surface, for science, resource development, or test beds for
planetary exploration technologies, will benefit from the development of
lunar resources. Because the Moon is a more likely venue for commercial
development than Mars, commercial opportunities may exist in lunar
resource development.

Two scientific issues link the Moon and Mars in this area. In both
cases, better understanding is needed of the distribution, form, and
concentration of the resources, particularly water, which is important
for production of propellant as well as human life support. The form and
concentration of deposits may determine the processes that can be used
for extraction. If the resources are to be extracted from surface
materials, better characterization is required of the physical
properties of surface materials (i.e., the regolith) to allow excavation
and movement of materials from the surface into processing systems.

Because of its important applications, water is probably the most
valuable early resource that will be produced on either the Moon or
Mars. Propellant production can be, but is not necessarily related to
production of water. A variety of other resources exist on both bodies
that will find application in human exploration and development
scenarios.

Three Moon-Mars themes were identified to fit within this topic:

-   *Water as a Resource*

-   *In-situ Fuel Sources*

-   *Exploration and Processing of Planetary Materials*

**Science-Based Technological Demonstrations on the Moon**

Because of its proximity to Earth, the Moon provides a functional
technological testbed for developing technical capabilities for the
scientific exploration the Mars by robots and by humans. Testbed
examination of robotic drilling, in-situ measurements, sample selection
and return, and astrobiological measurements may be accomplished on the
lunar surface. Deployment and testing of a seismic network and other
geophysical tools (i.e., heat flow) may be tested (and will produce
useful and high-priority science) on the Moon. Although most of these
probably could be done first on Mars, the technical feasibility of these
measurements can be significantly advanced and associated risks
mitigated on the basis of a lunar testbed experience.

Seven Moon-Mars themes were identified to fit within this subject:

-   *Communication & Ranging Systems*

-   *In-situ Resource Utilization (ISRU) Technology Demonstrations*

-   *Drilling Technologies*

-   *Seismic Net Technologies*

-   *Assess Bio-Organic Contamination*

-   *Sample Selection and Characterization technologies and Strategies*

-   *Sample Return Technologies*

**Astrobiology**

Astrobiology is the quest to understand how habitable planets form and
how inhabited worlds evolve, as well as the prospects for life beyond
the Earth (Jakosky et al., 2004). Therefore, astrobiology research
questions provide many linkages between lunar exploration and Mars
science goals. Broadly, these linkages can be divided into two
categories: historical and technological.

Historically, the Moon preserves unique information about events and
processes that have affected the habitability of the entire inner Solar
System, including early Mars. Such events include:

-   *Impact chronology (esp. during the first billion years)*

-   *The composition of large impactors, interplanetary
    dust-particle(IDP) flux, etc.*

-   *Delivery of exogenous volatiles and organics molecules*

-   *History of solar activity (solar wind; flares)*

-   *Occurrence of nearby supernovae and Gamma Ray Burst (GRB) events*

The record of such events is obscured on Earth. Although it is somewhat
better preserved on Mars, the lunar record is much more accessible.
Hence, the Moon is the ideal place to improve our understanding of some
of these events. In addition, the Moon can provide a testbed for
technologies designed to examine these issues on Mars. Rather than set
astrobiology apart as an isolated topic of investigation, the
astrobiological relevance of such linkages is woven throughout this
white paper.

Technologically, the Moon provides a uniquely accessible planetary-scale
sterile environment useful for assessing engineering goals of
astrobiological importance, especially for life detection and planetary
protection. For example, we can envision conducting control experiments
of life detection technologies to assess the potential for unanticipated
false positives in outside, highly controlled laboratory settings.
Additionally, the Moon is an ideal place to assess the effectiveness of
technologies designed to minimize "forward contamination" of other
planetary surfaces by robotic or human explorers.

**Prioritization**

As various science topics were identified by the MMSLSG, these were
organized into related science themes (A), resource themes (B), and
technology themes (C). These themes include the major lunar science
topics identified in the 1995 LExSWG report, plus some additional topics
that recognize the importance of martian volatiles within the
exploration program. Criteria to prioritize these themes were
established to rank them with regard to (1) understanding the Moon
within the context of major solar-system processes and (2) their
importance in better understanding Mars.

**Lunar Criteria**

Three criteria were identified by which to prioritize the Category A
science themes according to their importance to lunar science. These
criteria are:

1\) The intrinsic scientific value of each theme for advancing our
understanding of the Moon. This criterion evaluates the perceived
importance of each science theme without regard to the ease or
difficulty of being able to advance knowledge about that theme.

2\) The degree to which a potential set of investigations is likely to
make major contributions to answering major scientific questions posed
by the theme. This criterion evaluates the anticipated degree to which
various experimental approaches are likely to contribute significant
knowledge about the theme.

3\) Feasibility within the emerging strategy for precursor robotic lunar
missions in support of human exploration.

Slightly different criteria were used to rank the Category B resource
themes and the Category C technology themes. These were ranked in a
manner analogous to the A-themes:

1\) Overall importance of each theme to advancing the Moon-Mars
Exploration goals.

2\) The degree to which a given resource or test-bed endeavor is likely
to make contributions to characterizing a valuable resource or
developing an important process for use in the broad science exploration
program.

A subcommittee of the MMSLSG discussed and individually ranked each
investigation according to each criterion. The criteria rankings were
given equal weighing to derive an overall lunar science ranking for each
theme. The full MMSLSG established the final ranking of these
investigations. Rating of lunar investigations that were incorporated
into the prioritization based on Mars criteria are listed in Table 1.

**Table 1. Prioritization of lunar investigations based on lunar science
perspective. The investigations have not been rated within each priority
group.**

  ----------------- ----------------- ----------------- ------------------
                    Category A        Category B        Category C

  High Priority                                         

                    Structure and     Water as a        Sample Selection
                    Composition of    Resource          and
                    Planetary                           characterization
                    Interiors                           

                    Planetary                           Sample Return
                    Differentiation                     Technologies

                    Impactor Flux vs.                   Drilling
                    Time                                Technologies

  Moderate                                              
  Priorities                                            

                    Thermal &                           Seismic Net
                    magmatic                            Technologies
                    Evolution                           

                    Origin and                          Communication &
                    History of                          Ranging Systems
                    Exogenous                           
                    Volatiles                           

                    Planetary                           
                    Asymmetry                           

                    Regolith History                    

                    Interpreting                        
                    Geologic                            
                    Environments                        

                                                        

  Lower Priorities                                      

                    Energetic         Exploration and   ISRU Technology
                    Particle History  Processing of     Demonstrations
                                      Planetary         
                                      materials         

                    Origin and        In situ Fuel      Assess Bio-organic
                    History of        Sources           Contamination
                    Endogenic                           
                    Volatiles                           
  ----------------- ----------------- ----------------- ------------------

**Martian Criteria**

Four criteria were identified by which to prioritize the Category A
science themes according to their importance to martian science. These
criteria are:

1\) The intrinsic scientific value of each theme for advancing our
understanding of Mars if the investigation was first carried out on the
Moon. This criterion evaluates the perceived importance of each science
theme without regard to the ease or difficulty of being able to advance
knowledge about that theme.

2\) Degree of alignment with MEPAG's priority system for Mars
exploration (Appendix II).

3\) The degree to which a potential set of investigations is likely to
make major contributions to answering major scientific questions posed
by the theme. This criterion evaluates the anticipated degree to which
various experimental approaches are likely to contribute significant
knowledge about the theme.

4\) Degree of criticality of the possible lunar activity to one or more
future Mars missions (or surface measurement activities.

These criteria were not given the same weight in establishing
priorities. The criteria that reflected a strong linkage to Mars were
given a higher score.

Slightly different criteria were used to rank the Category B resource
themes and the Category C technology themes. These were ranked in a
manner analogous to the A-themes.

1\) If successfully carried out at the Moon, the value to our ability to
correctly plan and successfully implement the future Mars exploration
program.

2\) Importance that these measurements/demonstrations be carried out by
the lunar robotic program prior to 2020.

3\) General affordability of these measurements/ demonstrations.

4\) Our technical ability to carry out these measurements/
demonstrations by the lunar robotic program prior to 2020.

A subcommittee of the MMSLSG discussed and individually ranked each
investigation according to each criterion. The criteria rankings were
not given equal weighing to derive an overall Mars linkage ranking for
each investigation. The criteria that reflected a strong linkage to Mars
were given a higher weight. The full MMSLSG established the final
ranking of these investigations. In each category listed below,
investigations are ordered by prioritization based on Moon → Mars
linkages. Prioritization of lunar investigations based on martian
criteria is listed in Tables 2. Comparison between prioritization based
solely on lunar criteria and martian criteria is presented in Appendices
III and IV.

**Table 2. Prioritization of lunar investigations based on Mars science
perspective. The investigations have not been rated within each priority
group.**

  ----------------- ----------------- ----------------- ------------------
                    Category A        Category B        Category C

  High Priority                                         

                    Impactor Flux vs.                   Sample Selection
                    Time                                and
                                                        characterization

                    Origin and                          Sample Return
                    History of                          Technologies
                    Exogenous                           
                    Volatiles                           

                                                        Drilling
                                                        Technologies

  High-Moderate                                         
  Priorities                                            

                    Thermal &         Water as a        Seismic Net
                    magmatic          Resource          Technologies
                    Evolution                           

                    Interpreting                        ISRU Technology
                    Geologic                            Demonstrations
                    Environments                        

                    Regolith History                    

  Moderate          []{.mark}         []{.mark}         
  Priorities                                            

                    Origin and        In situ Fuel      Communication &
                    History of        Sources           Ranging Systems
                    Endogenic                           
                    Volatiles                           

                                                        Assess Bio-Organic
                                                        Contamination

  Lower Priorities  []{.mark}         []{.mark}         []{.mark}

  []{.mark}         Structure and     Exploration and   
                    Composition of    Processing of     
                    Planetary         Planetary         
                    Interiors         materials         

                    Planetary                           
                    Differentiation                     

                    Planetary                           
                    Asymmetry                           

                    Energetic                           
                    Particle History                    
  ----------------- ----------------- ----------------- ------------------

**Criteria for Overall Priorities**

The criteria for overall priorities are based on the overall priorities
established by the lunar and martian priorities.

1\) The importance of the investigation for understanding Mars as
defined by martian priorities (Table 2).

2\) The importance of the investigation for understanding the Moon as
defined by lunar priorities (Table 1).

The criteria rankings were not given equal weighing to derive an overall
linkage ranking for each investigation. The criteria that reflected a
strong linkage to Mars were given a higher weight. A more detailed
discussion of these criteria and prioritization of investigations are
discussed in the summary (Table 3 and 4).

**Relative versus Absolute Priorities**

We should emphasize some of the limitations of the set of priorities
that are presented in this document. Our analyses were deliberately
restricted (see \"Charter\", Appendix I) to consideration of those
scientific investigations and technical demonstrations which provide
linkages between goals for Mars exploration and those for lunar
exploration. Thus there are many crucial investigations on Mars which do
not figure prominently in our priorities, simply because the application
to the Moon is weak or nonexistent. Similarly there are important lunar
questions which are not addressed due to their lack of direct relevance
to Mars. Thus these priorities specifically reflect the importance of
the potential feed-forward of lunar investigations for Mars exploration.
In order that they are not taken out of context, it should be born in
mind that these are *relative priorities*, divorced from the intrinsic
value of the particular goals and investigations. The assignment of
absolute priorities, which would clearly be extremely useful, requires a
more far-reaching evaluation of NASA\'s scientific, exploration, and
programmatic goals, and is beyond the scope of this group\'s charter. 
For example, we were not asked to attempt a cross prioritization of
lunar investigations which may benefit Mars and investigations directly
at Mars.

> **Category A. Investigations related to the processes of terrestrial
> planet formation and evolution.**

**1. Investigation: Impactor Flux versus Time.**

The lunar surface has a unique record of the first billion years of
impact history and records the chronology of inner-solar-system
evolution in a cumulative form. The impactor flux places a boundary
condition and a time scale on planetary differentiation, the early
addition and loss of volatiles, and subsequent geological and biological
evolution. The martian time scale is thought to be similar to that of
the Moon, although the rate of collisions at Mars\' impact history might
be higher due to its close proximity to the asteroid belt. The lunar
crater production function depends on a few sample dates, with a
multi-billion-year gap between the Imbrian and Copernican ages. To first
order, this function is thought to be uniform, although significant
deviations may exist. Likewise new studies indicate that early basin
production may also be non-uniform. To address these issues - as well as
to counter the crater saturation effects that can affect crater
size/density distributions on uniform and datable lunar surfaces -
better relative and absolute calibration are required. Furthermore,
inferences on the source of impactors in the solar system responsible
for the observed cratering distribution can be obtained from their
compositional properties.

***Measurements:*** The lunar investigation requires age determinations
of uniform surfaces of varying ages where impact melts and volcanic
flows are present. Additional remote observations of crater
distributions in conjunction with such age measurements are critical.
The composition and stratigraphy of highland ejecta need to be
determined so as to trace samples back to their origins. Compositional
variations of impactors with time need to be correlated with possible
multiple changes in the source of impactor in the solar system, and with
cataclysmic events in the early solar system. A better understanding of
the physical and geochemical effects of both basin-scale and smaller
impactors will contribute to the calibration of the impact time scale.

**2. Investigation: Origin and History of Exogenous Volatiles.**

***Moon-Mars Science:*** Being a volatile-poor body, most volatiles on
the lunar surface derive from the solar wind or from volatile-rich
objects (e.g., comets) that collide with the Moon. Evidence for
significant hydrogen concentrations near the lunar poles have led to the
suggestion that polar regions perpetually in shadow may contain various
cometary volatiles, including water, which could be used as a resource.
Compared to the Moon, Mars is a volatile-rich object for which the
exogeneous or original complement of volatiles has been partly modified
throughout martian history. Differentiating between those volatile
characteristics inherited by Mars and those generated over time is
important to understand the origin and evolution of the atmosphere,
interactions between the atmospheric and surface, and whether compounds
necessary for life might have been present on early Mars. Study of
ancient volatiles trapped at the lunar poles, if such can be identified,
may help to define the composition of early cometary volatiles on Mars.

***Measurements:*** Lunar investigations require detailed composition
and isotopic measurements of volatile components possibly trapped in
perpetually shadowed areas near the lunar poles. Drilling or other means
of access to the subsurface may be required to access ancient volatiles
and to decipher how volatiles become concentrated at the poles. Martian
investigations may require the detailed compositional and isotopic
measurements of volatile components that are trapped within the Martian
crust and that have not been significantly altered over time.

**3. Investigation: Decipher planetary thermal and magmatic evolution.**

***Moon-Mars Science:*** Although the Moon and Mars formed and evolved
in different ways, deciphering the thermal and magmatic evolution of
each is fundamental to understanding the dynamics of their interiors and
the expression of mantle processes on their surfaces (Shearer and
Papike, 1999). For Mars in particular, it is important to evaluate
whether thermal and magmatic processes may have provided energy and
suitable habitats for the development of life. For lunar science, this
investigation will track the dynamics of the lunar interior and changes
in those processes with time. Shallow and surface processes, too, will
be evaluated including the nature and location of basalt sources over
time, variations in rates of magma production over time and space, and
the history of crust and lithosphere growth. Similarly for Mars, this
investigation will evaluate igneous processes through time and evaluate
the vertical structure, chemical and mineralogical composition of the
Martian crust. In addition, it will be important to evaluate the extent,
locations, and persistence of geothermal heat that might have supported
a subsurface biosphere.

***Measurements:*** Despite the differences in formation and evolution
of the two bodies, an investigation such as this will use similar
techniques to investigate similar geologic processes. For the Moon, the
investigation will require defining the distribution, composition, and
age of basalts that pre-date basin formation and those that represent
the last stages of mare volcanism. Similarly, the distribution of
heat-producing elements, to evaluate heat flow, and the
chemical/isotopic composition of volcanic rocks both within and outside
the more volcanically active region need more detailed investigations.

**4. Investigation: Interpreting Geologic Environments**

***Moon-Mars Science:*** Determining how materials found at the planet's
surface formed, whether at the surface or in an interior setting, is key
to understanding past and present geologic environments. On the Moon,
where the surface is dominated by impact craters and deposits at all
size scales, the capability to read the geologic history as recorded in
minerals and rocks is crucial to understanding original igneous
relationships, whether intrusive or extrusive, and to distinguish the
different facies of impact-generated materials. Almost all lunar surface
formations are part of the regolith and have been displaced from the
site of their origin. Thus the capability is needed to determine
composition, mineralogy, and texture of a rock to interpret what
geologic formation it came from and thus to understand its origin.
Knowing the global distribution of rock types and geologic formations is
one of the keys to evaluating crust formation and modification
scenarios. Thus mineral and rock determination and detection is needed
on the scale of individual rocks at the surface of the planet as well as
from orbit.

In addition to relationships described above, Mars' past geologic
environments include water interactions at the surface and in the
subsurface, and interaction with the atmosphere. The latter continues
today. Thus an additional and extremely important priority for Mars
exploration is to investigate rocks formed at or near the surface in
sedimentary or hydrothermal environments, and those altered by physical
and chemical weathering. The capability to determine mineralogy, rock
type, and rock textures and fabrics are also key to understanding the
environment in which they formed or were altered.

***Measurements:*** Lunar minerals and rock types are well known from
the lunar samples, and the distribution of major rock types (or mixtures
thereof) as reflected by regolith and megaregolith compositions sensed
remotely from orbit is known to a crude first order. However, the rock
types and variations that occur locally, on a scale that would be of
concern for further scientific exploration and for possible development
of the Moon, including resource evaluation and exploitation, are not
well known for other than the Apollo landing sites. Further unmanned
lunar investigations need the capability to determine mineralogy and
rock type/texture. On the surface, in-situ methods are required that can
determine definitive mineralogy and lithology from fixed or mobile
(roving) platforms. For locations that are inaccessible to such
platforms, standoff capabilities (m to 10's of m) are needed. Available
remote sensing includes Earth-based spectroscopic data and crude orbital
multispectral data; modern hyperspectral measurements and global
coverage with high mineral specificity and spatial resolution are
needed. For Mars, these same general measurement requirements exist, but
the breadth of mineralogy to which instruments must be sensitive is
greatly expanded by the presence of water and potential enrichments of
other volatile elements, and by more oxidized surface conditions.
Orbital remote-sensing exploration to date is far superior for Mars than
for the Moon.

**5. Investigation: Characterize the structure and composition of
planetary regoliths.**

***Moon-Mars Science:*** Characterizing the structure and composition of
lunar and martian regoliths is critical to our understanding of the
development of the outer skin of planets; this fragmental outer skin
includes much of the material seen in multispectral observations from
telescopes and from missions. While detailed studies of the lunar
regolith have been done for the Apollo and Luna returned samples, we do
not yet have good age and rate control for the many complex processes
that produce and modify the lunar regolith. Such time control can be
acquired by sampling fossil or buried regolith sandwiched between
datable lava flows or impact-melt rock layers using either drill cores
or impact crater walls to sample the fossil regolith. Armed with this
time control, we can determine the rate at which regoliths are formed,
and whether that rate has varied over geologic time, we can determine
the production rate for agglutinates and other impact-melt phases, we
can determine the variation of grain size and size-distribution curves
with accurately known exposure time, we can determine the build-up rate
for individual solar-wind species, and we can determine the lateral
transport rate by characterizing the degree of contamination of local
material by distant material. The Moon constitutes the end member in a
spectrum of planetary regoliths formed by a combination of physical and
chemical processes. Earth is at the other end, and Mars is in between.
As an end-member, the Moon is critical to understanding both the
absolute rates of regolith formation and alteration, and the relative
rates of the processes that alter the regolith. For Mars, the lunar data
on these rates provides a starting anchor point for assessing the
relative intensities of impact regolith-producing processes and chemical
and physical weathering processes. This anchor point can only be
established using carefully age-dated fossil regoliths.

***Measurements:*** For the Moon, these studies require carefully
located regolith sandwiched between datable volcanic or impact melt rock
units. The necessary detailed studies can only be done on returned
samples. The best sampling approaches are core samples (10's of meters
will be necessary) or from sidewall sampling of craters that have
penetrated fossil regolith "sandwiches" bounded by datable rocks.
Ideally, samples should come from the both oldest and the youngest
volcanic terrains. Areas with relatively short time intervals between
flows would be ideal. In highland regions, identifiable overlapping melt
sheets from larger impacts or even basin-forming impacts might provide
good age control. For Mars, a better understanding of the martian
regolith is required before pursuing this line of investigation.

**6. Investigation: Origin and History of Endogenic Volatiles.**

***Moon-Mars Science:*** Characterization of the presence and
distribution of volatile elements among planetary bodies provides
fundamental information on differentiation processes and the mechanisms
of planetary formation in the Solar System. On the Moon, volatile
elements from endogenic processes or internal sources such as volcanism
are rarely found. Unlike the Earth, lunar materials show little sign of
the past presence of water; CO~2~ and CO gases were probably the
dominant volcanic gases on the Moon. The major exceptions are the
volatile-element enriched coatings found on samples of pyroclastic glass
beads from the Apollo 15 and 17 landing sites. These volatile- and
metallic-element (Fe and Ti) enriched remnants of ancient volcanic
eruptions on the Moon provide clues to the nature of the early lunar
interior and to the distribution of potential resource materials for
future exploitation. By contrast, minerals and gases from Mars may be
substantially more enriched in water. This investigation allows us to
understand the varieties, abundances, and distribution of volatile
elements released from the lunar interior, to characterize their depths
of origin, and to understand the processes controlling their loss and
possible transport to regions such as the lunar poles. Characterization
of lunar endogenic volatiles provides context for studies of endogenic
and exogenic volatiles on Mars, and may lead to a more comprehensive
understanding of the surface and subsurface distribution of volatile
species on Mars, how these may have changed through time, and the origin
and evolution of the martian atmosphere.

***Measurements:*** The lunar investigation requires in-situ examination
and sampling of lunar pyroclastic deposits, compositional studies of
their surface coatings and interiors, and petrologic analysis of their
depths of origin. In addition, this investigation requires
identification, characterization, and sampling of volatile reservoirs at
the lunar poles, with emphasis on comparative analyses of endogenic
versus exogenic volatile species.

**7. Investigation: Early Planetary Differentiation.**

***Moon-Mars Science:*** The Moon and Mars underwent planetary-scale
differentiation early in their histories that may have involved early
core formation followed by the crystallization of magma oceans on these
bodies. A record of this earliest phase of differentiation on both
bodies is preserved in the structure and composition of their interiors
and in the range of ancient rock types exposed on their surfaces.
Therefore, an understanding of the earliest differentiation history of
the Moon could help to place constraints on the mechanisms and time
scales involved in similar processes that may have occurred on Mars. The
style of differentiation may partially dictate the pathway along which a
planetary body may evolve. Investigation of early lunar differentiation
history can be done through detailed characterizations of the internal
structure of the Moon as well the compositions and ages of the rocks
from the far-side lunar highlands and those exposed in large impact
craters and basins.

***Measurements:*** This lunar investigation would require geophysical
as well as geochemical and petrographic measurements. The geophysical
measurements require the establishment of a global network of
seismometers that would help to resolve the deep and shallow structure
of the Moon. The geochemical and petrographic measurements require the
sampling and analysis of lunar rocks from the ancient highlands
(particularly from the far-side, which are not represented in the Apollo
collections) as well as those representing deep crustal lithologies that
have been exposed at the lunar surface by large impacts.

**8. Investigation: Characterize the structure and composition of
planetary interiors.**

***Moon-Mars Science:*** Characterizing the structure and composition of
planetary interiors is fundamental for understanding the origin and
differentiation of a planet, dynamical mantle processes, surface
evolution, tectonics, magmatism, and magnetic field. This investigation
provides constraints for the bulk composition of the Moon, its origin,
and the manner in which it differentiated. Characterization of crust,
mantle, and core structural domains anchors our understanding of lunar
asymmetry, mantle dynamics, magnetic field, and the current thermal
state of the Moon. The lunar structure provides a record of early
planetary processes that may prove essential to the interpretation of
basic mechanism of martian differentiation and early dynamical processes
of the martian interior. This may lead to a more comprehensive
understanding of early Mars: the nature of the primordial crust, the
origin of the hemispheric dichotomy, the release of water from the
mantle, and evolution of the early magnetic field and its effects on the
atmosphere and radiation shielding.

***Measurements:*** The lunar investigation requires high-resolution
seismic, far-side gravity and topography measurements. These geophysical
measurements require the establishment of a global seismic network
consisting of multiple seismometers. Far-side gravity and topography
measurements must be made using orbital spacecraft. In addition to
geophysical measurements, this investigation also requires examination
and sampling of deep crustal lithologies that are exposed at the lunar
surface and basalts that are outside of the Apollo era collection sites.
These samples provide windows into the Moon's lower crust and mantle.

**9. Investigation: Planetary Asymmetry.**

***Moon-Mars Science:*** Both Moon and Mars exhibit asymmetry in
composition and structure on a global scale. On the Moon, asymmetry is
manifested by the distribution of rock types and thickness of crust, an
offset between center of figure and center of gravity, and by the
distribution and extent of volcanism (Jolliff et al., 2000). The lunar
crust is thicker and the feldspathic lunar highlands are concentrated on
the eastern lunar near side and on the northern far side. Volcanism is
most extensive on the western lunar near side, and that area appears to
have been a locus of extended igneous activity relative to other parts
of the Moon. On Mars, a north-south hemispheric dichotomy exists, with
older and more rugged highlands to the south, and a smoother, resurfaced
character in the northern hemisphere. Causes of these two different
manifestations of planetary asymmetry are unknown. They may be related
to early differentiation, early giant impact bombardment, or subsequent
modifications by internal processes. In the case of the Moon, the
asymmetry appears to be related to earliest differentiation of the
planet into crust and mantle resulting from solidification of a global
magma ocean, and the effects of asymmetric distribution of
heat-producing materials may have played a key role in the subsequent
2-3 billion years of thermal and magmatic evolution. In the case of
Mars, relationships between planetary asymmetry and thermal and volcanic
evolution are as yet unknown.

***Measurements:*** Key to understanding planetary asymmetry is to
characterize the internal structure, distribution of rock types and
compositions, ages of different geologic terranes (broad regions that
experienced a common geologic history), and heat flow from the interior.
Specific investigations include seismic networks, gravity (lunar
far-side gravity is not well known), heat flow (distributed network),
and accurate topography/altimetry (lunar topography is not well known in
comparison to Mars). In-situ geochemical analyses at key surface
locations and improved global geochemical measurements (e.g., X-ray
spectrometry) are also needed. Ages of rocks from a variety of locations
and an understanding of the setting in which they formed (see A10) are
also needed.

**10. Investigation: Energetic Particle History.**

***Moon-Mars Science:*** Throughout solar-system history the lunar
surface has acted as a collector for the solar wind and solar and
galactic energetic particles (Rao et al., 1994). From studies of the
lunar regolith we have gained a better understanding of the composition
and energetics of particles that stream from the Sun and of the likely
isotopic composition of some volatile components in the early nebula
from which the planets formed. The relative elemental and isotopic
composition of implanted solar wind and energetic solar particles, as
measured in a variety of lunar regolith phases, is generally easier to
determine than is the flux and energy distribution of highly energetic
solar protons over past eons. Yet, the highly energetic solar (and
possibly galactic) particles have been the greater influence on the
evolution of the atmospheres of Mars and the Earth. Most of the
lunar-acquired information about solar particles characterizes solar
emissions over the last \~2 billion years, as ancient, undisturbed
regoliths have not been easily identified or accessible. Energetic solar
and galactic protons create nuclear reactions on the surface of many
solid planetary bodies, and through such reactions the composition of
some elements can be determined from orbit. In the case of Mars, charged
solar particles are attenuated within the atmosphere, where they serve
to erode the upper atmosphere over time, producing mass-fractionation
effects in some species. Highly energetic galactic particles produce
nuclear products in the surfaces of the moon and Mars, and this process
can be used to study regolith formation and mixing. This application of
GCR particles, however, is covered under theme A4 above.

***Measurements:*** For the Moon new information about the composition
of solar emissions can come from studying preserved paleo-regoliths or
basalt surfaces, which can be accessed by drilling to ancient basalt
flows or by accessing benches within crater walls. To determine the flux
and energy distribution of very energetic solar particles requires very
specialized samples in which depth profiles of nuclear products can be
measured. Whereas paleoregoliths may be common and accessible in basalts
\~3-4 giga-years in age, optimal materials \>4 giga-years in age may
have been strongly altered by the intense early bombardment and may be
difficult to find. For Mars direct study of solar emissions is probably
not possible. The effects of energetic particles on the atmosphere of
Mars today can be understood through orbital measurements of atmospheric
escape processes and through study of the isotopic compositions of
certain volatile species in the atmosphere and the solid planet.

**CATEGORY B. Evaluate human-related resource issues on the Moon to
better predict their state/usefulness on Mars.**

**1. Investigation: Water as a Resource.**

***Moon-Mars Science:*** Water is an important resource for human
exploration missions and can be used both for life support and for
fuel.  Both the Moon and Mars are suspected and known, respectively, to
have significant quantities of water at or near the surface and in the
atmosphere.  Water can presumably be extracted directly from the lunar
environment in the polar regions where it appears to be segregated in
permanently shadowed craters.  The source for water in the lunar polar
craters is assumed to be from comets.  Water can also be manufactured
from H and O both of which are widespread across the lunar surface.  H
is implanted by solar wind; O occurs within the regolith, derived from
the lunar basalts.

        Water is critical for human survival.  Even in a closed-loop
system there are some losses that must be replaced.  Having a supply of
in situ water (direct or manufactured) eliminates the need to bring it
from the Earth.  The constituents of water (H and O) are critical
elements for fuel, both rocket engine propellant and fuel cell
materials.

***Measurements**:* H is known to be widespread across the lunar surface
and has been measured directly in returned samples of the regolith and
detected by secondary neutron spectroscopy at both equatorial and polar
latitudes.  The H that occurs in the polar environment is interpreted to
be in the form of water ice, but water ice has not been unequivocally
confirmed.  O is an important element in lunar basalts and has been
measured in returned samples.  The critical measurements for use of
water as a resource would be to determine the amount, purity, and its
form (e.g., massive vs. dispersed ice) in permanently shadowed lunar
craters.  Having an understanding of the quantity, quality and form of
the water would allow an assessment of the relative merits of mining H
and O as separate phases compared with the mining of polar water ice and
of the types of techniques to be employed for extraction.

**2. Investigation: In situ Fuel Sources.**

***Moon-Mars Science:*** The lunar and Martian regoliths contain
potential components of rocket propellant that could be produced
*in-situ*, avoiding the need to transport them from Earth. Water and
carbon compounds, if present at the lunar poles, solar wind hydrogen and
carbon in the regolith, and oxygen produced by reduction of ilmenite or
pyroclastic glass are the principal potential sources on the Moon. On
Mars, there may be significant concentrations of bound water in the
regolith and accessible liquid water beneath, which could be used for
producing hydrogen/oxygen propellant or, in combination with carbon
dioxide from the atmosphere, methane and oxygen. These constituents also
could be used as fuel for fuel cells or as expendables for human life
support systems. The extraction of propellant from regolith minerals
would use similar approaches for both Moon and Mars, including
excavation, thermal extraction, water electrolysis, and oxygen, hydrogen
or methane liquefaction. A lunar propellant production demonstration
could influence the design of human missions to Mars as well as
demonstrate the validity of the concepts for propellant production from
the regolith on Mars.

***Measurements:*** The principal uncertainties in the lunar database
with respect to propellant production are the distribution, form,
concentration, and the physical properties of hydrogen-containing
deposits in permanently shadowed areas at the lunar poles. Better
understanding of the 3-dimensional distribution of carbon and hydrogen
in the non-polar regolith could be important. The economics of lunar
propellant production are highly sensitive to the concentration of
hydrogen (or hydrogen and carbon) because these are typically the least
abundant of elements on the Moon, so that finding locations that have
much larger concentrations than the average is important. Because the
scale of a useful polar ice deposit can be quite small (100 m^2^ x 3 m
deep regolith could produce 6 metric tons of propellant if the water
concentration is 1%, 30 metric tons if the concentration is 5%), lunar
surface exploration will be required, with subsurface detection
capability that may be provided by a drill or similar sampling tool.
Measurements should include: determination of the form of hydrogen and
other volatiles by mass spectrometry and differential thermal analysis;
local distribution of hydrogen and ice, by active neutron spectroscopy
and sub-surface electromagnetic sounding; and physical properties of
surface and sub-surface materials by cone penetrometer or analysis of
drilling or other mechanical system that interacts with the surface. The
capability to determine the isotopic composition of hydrogen and carbon
would add scientific value, but is not required for resource evaluation.

**3. Investigation: Exploration and Processing of Planetary Materials.**

***Moon-Mars Science:*** Demonstration of identification and processing
of resources in lunar missions can validate their use in Mars missions.
Many non-volatile materials can be manufactured from natural oxides and
silicates occurring in the regolith on the Moon or Mars. Systems need to
be developed to process planetary materials at surface environments with
similar constraints -- low ambient pressure, partial -- gravity.
Exploration for the distribution of resources from orbit and with new
techniques on surface is needed. Surface exploration techniques are
needed to establish mineralogy of martian materials that could provide
resources -- e.g. X-ray diffraction; differential thermal analysis. A
wide variety of manufactured products could be made from Martian
regolith -- glass, ceramics, composites that could assist human
exploration

***Measurements:*** Demonstrate the ability to identify resources on the
lunar surface. Demonstrate the ability to extract minor/trace
constituents from lunar regolith through physical beneficiation and
chemical extraction.

**CATEGORY C. Demonstrations at the Moon to gain experience, mitigate
risk, improve performance, and confirm capability.**

**1. Investigation: Sample Return.**

***Moon-Mars Science and Technology Linkage:*** Sample return missions
allow the full range of analytical techniques, available in laboratories
on Earth, to be used to extract qualitatively and quantitatively the
maximum information from a given returned sample. This allows high
sensitivity, high precision, and low contamination studies to be
performed in an optimum fashion. Complementary investigations can be
done in sequence and in consortium modes. Specific investigations can be
suggested based on detailed prior investigations on the same samples.
Furthermore, parts of the returned samples are routinely saved, in their
pristine condition, and are available as new analytical techniques are
developed and new imaginative investigators become interested in the
unique returned samples. For example, for the Apollo returned samples:
a) U-Th-Pb techniques with sufficiently low contamination were developed
several years after the end of the Apollo missions and permitted the
identification of the putative Lunar Cataclysm at 4.0 Ga ago; b) the
Sm-Nd dating technique was developed seven years after return of the
samples and was applied successfully to measure ages and to identify the
long-term preservation of mantle sources for mare basalts; c) thirty
years after return of the samples, new techniques for platinum group
elements, using negative ion mass spectrometry, were developed and
applied to identify the detailed nature of the exotic (meteoritic)
components in the lunar regolith and in lunar breccias, which trapped
the contributions to the Moon at \~ 4 Ga ago.

***Demonstrations:*** The development of capabilities for samples
returned from the Moon has direct application to techniques applicable
to samples returned from Mars. In particular, the detailed and
meticulous work required for the search for conditions compatible with
the development of life on Mars, and possible evidence for past or
present life on Mars may require the use of full-up, high sensitivity
and specificity analytical techniques, available in terrestrial
laboratories. Similarly the techniques developed to address the thermal
evolution and the development of a crust, mantle, and core on the Moon,
have direct applicability to the similar evolution of Mars. There is a
need for additional samples returned from the Moon, since the Apollo and
Russian missions were restricted to the equatorial regions on the Moon.
Specific scientific investigations on the Moon would take advantage of
the potential return of new samples from the back side of the Moon, the
South Pole-Aitken Basin, and the lunar poles. The specific scientific
questions to be addressed include better definition of the early impact
history of the Moon and inner solar system (e. g., especially prior to
4.0 Ga) and the better understanding of the development of the lunar
magma ocean and the preservation of distinct chemical and isotopic
reservoirs within the lunar mantle, which served as sources for the mare
basalts erupted in the interval 4-3 Ga. Samples can be returned from the
Moon and from Mars with relatively simple in-situ characterization
techniques, in order to pick interesting and non-redundant samples.
Limited mobility on the surface is acceptable given the effective
mechanisms for mixing materials on the regoliths of both planets.

**2. Investigation: In situ Analysis for Improving Sample Selection
Strategies.**

***Moon-Mars Science and Technology Linkage:*** Robotic spacecraft will
continue to be the method of exploring Mars for a significant period of
time and will be used as both precursors to and contemporaneous with
human exploration of Moon. The ability of these robotic systems to
analyze material either for complete in situ analysis or a screening
tool for the selection of samples to be returned to the Earth provides a
powerful enhancement of the total science. The ability to conduct
relatively sophisticated mineralogical, molecular, chemical and isotopic
analysis on both silicate materials and ice can provide substantial
insight into the nature of the material, be it lunar or martian, rock or
ice. The evolution of capability from the first Surveyor measurement to
those made by the MER rover show how much can be learned from in situ
analysis.

***Demonstrations:*** Additional capabilities are in various stages of
development and both demonstration and use on the Moon, as a prelude to
Mars, will result in increased science return.

**3. Investigation: Drilling Technologies.**

***Moon-Mars Science and Technology Linkage:*** The surfaces of Mars and
the Moon are characterized, over large regions, by regoliths comprised
of mixed dust and rock. Many scientific questions require access to the
subsurface. For example, there are likely to be few volatile species
within the upper 10 cm of the lunar regolith due to solar wind exposure.
Likewise, many compounds of interest for astrobiology are more likely to
lie below the surface of Mars, shielded from UV exposure. Subsurface
sampling also holds the potential for obtaining a time record of climate
(Mars) or solar wind fluctuations (Moon). The capability to drill to
depths of perhaps several meters, and to return "pristine" samples, is
thus of high priority for the Moon and Mars.

***Demonstrations:*** Drilling in planetary regoliths presents a number
of challenges. Astronauts found it difficult to obtain cores from the
lunar regolith, which is well compacted below the upper few cm. Robotic
planetary drilling or scraping to date has been performed only to depths
of a few cm, and there is considerable development needed to demonstrate
the capability.

**4. Investigation: Seismic Technologies-Studies.**

***Moon-Mars Science and Technology Linkage:*** A seismic network is
required to understand the inner workings of any solid planetary body.
The Apollo program deployed 4 seismometers, but all were on the
near-side, relatively close to each other and installed by astronauts.
The structure and composition of the lunar deep interior is still
unknown as is the crustal structure on the far side. Such a network
would be critical for the characterizing the depth of regolith in some
regions, defining crustal/mantle heterogeneity, and delineating the
composition and size of the lunar core. It would also test the lunar
magma ocean hypothesis. Installation of a lunar seismic network would
provide insights into deploying a robust seismic network on Mars. The
Moon provides a testbed environment that is in close proximity to Earth,
and is seismically quite requiring long-lived and sensitive
seismometers. A martian seismic network could acquire evidence of
continuing tectonic (magmatic) activity, nature of the internal
structure and composition, and characterization the shallow subsurface
in some regions (e.g., extent of potential aquifers). In addition to
seismic studies of the Moon and Mars, the developing the ability to
deploy a network on a planetary surface is fundamental to studies of
other terrestrial planets and moons.

***Demonstrations:*** An important demonstration would be the deployment
of sensitive, broadband seismometers on both the near side and far side
of the Moon. This would test technical approaches for emplacing highly
sensitive seismometers on a planetary surface and operating them over
extended periods of time. Additional geophysical tools could be added to
the seismic tools.

**5. Investigation: Assess Bio-Organic Contamination.**

***Moon-Mars Science and Technology Linkage:*** The search for evidence
of *extant* life on Mars requires the development and application of
novel technologies to detect signs of biological activity. In addition,
this search requires that the risk of forward contamination of the
Martian surface by terrestrial microbes be minimized during future
exploration activities. Such contamination could also perturb the
Martian biota, if it exists. The interpretation of biosignatures of
*extinct* life, such as carbon isotope variations, might also be
complicated by the activity of modern microbes, or by biogenic
compounds, brought to Mars from Earth. The same holds true for
investigations into molecular precursors of life, such as organic
compounds.

***Demonstrations:*** The lunar surface is a completely sterile
*natural* environment. Therefore, the Moon offers a unique opportunity
to assess Mars-bound technologies and protocols designed to detect signs
of life as well as those intended to minimize forward contamination.
Such testing is impossible on Earth outside of idealized conditions in
the laboratory. Life detection approaches intended for Mars could be
tested in control experiments on the lunar surface to minimize the risk
of future "false positives" or other ambiguities on Mars. The risk of
forward contamination could be assessed by sensitive analyses of organic
compounds, microbial residues and surviving organisms on and around
future lunar spacecraft.

**6.** **Investigation: ISRU Technology Demonstrations**

***Moon-Mars Science and Technology Linkage:*** The use of in-situ
resources on either the Moon or Mars will not become reality before
there are demonstrations, probably at the level of robotic mission
experiments that have sufficient robustness to demonstrate the viability
of the technology to extract and process the planetary resources. The
most important demonstration will be the first one, whether it is done
on the Moon or on Mars. This will remove a level of uncertainty in a
manner similar to that in which the demonstration of ion propulsion on
the Deep Space 1 mission cleared the way for a myriad of applications of
the technology on subsequent missions. Although the surface environment
and contents of useful materials are different for the Moon and Mars,
there are some cases in which the extraction technology may be similar
(for example, extraction of ice or solar wind volatiles from the
regolith on the Moon and extraction of water from hydrated regolith
minerals on Mars) and for many processes, subsystem elements can be
common (for example, excavation and materials handling systems, heating
chambers, Sabatier reactors, gas and fluid handling, water and CO~2~
electrolysis, and H~2~, O~2~ and CH~4~ liquefaction). For systems such
as these, which transport solids, liquids and gases, in some cases in
multi-phase systems, the behavior of the systems at reduced gravity will
have to be demonstrated before the technology can be adopted for
missions.

***Demonstrations:*** Testing the extraction and/or production of water,
hydrogen, oxygen and methane is generally regarded as the highest
priority because of the application of these products in spacecraft
propellant and for human life support systems. Demonstration of the
specific technologies for accomplishing these processes, either for the
lunar polar shadowed craters, where some of the products may exist, or
for typical lunar regolith, will be a first step toward eventual
deployment for human and robotic missions. There are several approaches
to demonstration that must be considered. These include: (1)
demonstration of the subsystem components (e.g. valves, Sabatier
reactors) in the relevant environment; (2) end-to-end demonstrations of
complete systems, preferably with long enough production times to
provide information on the robustness or expected lifetime of systems in
the lunar environment; and (3) full demonstrations of extraction
technologies aimed at providing data suitable for scaling to production
quantities. These should be selected depending on the maturity of the
Earth-based technology, adequate models to predict performance in the
lunar environment, and to some extent, development schedule compared to
the expected time at which the technology would be used. The highest
priority demonstrations would appear to be: (1) extraction of water or
hydrogen from lunar polar soils, conversion to H2/O2, and liquefaction
of H2 and O2.; (2) production of oxygen from either mare or highlands
regolith; (3) demonstration of the use of one or more of these compounds
on the lunar surface, which would require transfer of the compounds to a
test article, such as a hopper or a fuel cell on a rover.

**7. Investigation: Communication and Ranging Systems.**

***Moon-Mars Science and Technology Linkage:*** Lunar surface science
goals, such as a global seismic network or South Pole-Aitken basin
studies, may require landings on the far side. Potential areas of
exploration at the lunar poles may also be out of direct line-of-site
contact with Earth during all or part of the year. Communications with
surface experimental packages thus require an orbital relay capability.
Measurements of the gravity field for the lunar far side will also
require at least two orbital spacecraft that can be used to measure
relative velocity shifts. In the most capable mode, such orbital assets
could form a global positioning system for the Moon, which could be used
for long-term studies of internal structure. A similar "Mars GPS"
network could improve the geodetic grid, allow enhanced studies of
internal structure, and provide continuous communications with landed
packages.

***Demonstrations:*** Given current terrestrial GPS capabilities,
relatively little technology development is required to achieve the
Moon-Mars goals. There is also little need for this technology to be
first demonstrated at the Moon.

**FINAL PRIORITIES**

The final priorities in this report are summarized in Tables 3 and 4.
Although we did not attempt to develop a detailed cross-prioritization
of all 20 elements, but the comparative priorities of elements in the
two lists can be seen in a general way; e.g. a high priority item in
list A can be assumed to be of generally higher overall priority than a
low priority item in list B+C. A more detailed implementation guide for
selected science themes are outlined in Appendix IV in an "AO style"
format. These investigations and demonstrations are prioritized based on
their linkage to Mars exploration. Highest scientific priorities
recognized by this steering group were Impactor Flux versus Time and
Origin and History of Exogenous Volatiles (Table 3). There appears to be
no scientific investigation that must be done on the Moon prior to the
investigation being done on Mars. However, in many cases, the Moon
provides a planetary frame of reference for better understanding Mars.
For example, the Moon provides an example of one style of planetary
differentiation: Magma Ocean. How far early differentiation deviates on
Mars from this style of differentiation is important for understanding
the origin of Mars and the pathway on which it evolved.

As discussed above, the lunar science (A category) themes
(Investigations related to the processes of terrestrial planet formation
and evolution) were ranked into three categories (Table 1) based on
overall importance to advancing scientific understanding of the Moon and
the degree to which identified investigations are likely to make major
contributions to advancing knowledge about the important science
questions. The ten lunar science themes were also ranked into four
categories according to how strongly they linked to MEPAG Investigations
(Table 2). These procedures allow a hierarchical scheme that builds on
these two results to establish *Overall Science Priorities* in
Moon-to-Mars science links. These priorities reflect, simultaneously, an
attempt to answer two questions: "How strongly is the lunar science
theme connected to MEPAG goals?" and "How important is the theme, in and
of itself, for advancing lunar science?"

The *Overall Science Priorities* were slanted towards Mars science goals
as the MMSSG Charter makes it clear that the SSG should consider first
and foremost how to define science-based activities on the lunar surface
that would benefit the scientific exploration of Mars. Thus in
establishing an overall priority, a strong linkage of a lunar theme to a
MEPAG Investigation trumps a theme that has a strong lunar science
impact but is less linked to MEPAG goals for Mars.

**Table 3. *Overall Science Priorities*.**

**[HIGH PRIORITY\
]{.underline}**Impactor Flux vs. Time

Exogenous Volatiles

**[HIGH-MEDIUM PRIORITY\
]{.underline}**Thermal and Magmatic Evolution

Interpreting Geologic Environments

**[MEDIUM PRIORITY]{.underline}\
**Endogenous Volatiles

Interior Planetary Structure

Early Planetary Differentiation

Regolith History

**[LOW PRIORITY\
]{.underline}**Planetary Asymmetry

Energetic Particle History

Categories B and C were also rated in a similar manner. High to Medium
priority technology demonstrations include: in-situ sample selection and
analysis, sample Return technologies, drilling technologies, ISRU
Technology Demonstrations, seismic technologies/Studies, and water as a
resource (Table 4). These technology demonstrations need not be done on
the Moon prior to Mars. However, as exploration drives martian science
to new levels of complexity prior demonstrations on the Moon will refine
exploration strategy, diminish risk, and improve performance.

**Table 4. *Overall lunar technology (Categories B and C) priorities
based on linkages to Mars exploration.***

[**HIGH- MEDIUM PRIORITY:**\
]{.underline}In-situ sample selection and analysis

Sample Return

Drilling technologies

**[MEDIUM PRIORITY (higher):]{.underline}**\
Seismic technologies/Studies

Water as a Resource

**[MEDIUM PRIORITY (lower):]{.underline}**\
In-situ fuel resources

Assess Bio-Organic Contamination

[**LOW PRIORITY:**\
]{.underline}ISRU Technology Demonstrations

Communication and ranging systems

Exploration and Processing of Planetary Materials

**REFERENCES**

Benz, W. and Cameron, G.W., ***Terrestrial effects of the giant
impact,*** In: Origin of the Earth (H.E. Newsom and J. Jones, eds.)
Oxford Univ., New York, 1990, 61-68.

Jakosky, B., A. Anbar, G.J. Taylor, and P. Lucey, ***Astrobiology
science goals and lunar exploration: NASA Astrobiology Institute white
paper*,** NASA Astrobiology Institute, July 19, 2004, 12 pp.

Jolliff, B.L., Gaddis, L.R., Ryder, G., Neal, C.R., Shearer, C.K.,
Elphic, R.C., Johnson, J.R., Keller, L.P., Korotev, R.L., Lawrence,
D.J., Lucey, P.G., Papike, J.J., Pieters, C.M., Spudis, P.D., and
Taylor, L.A., ***New Views of the Moon: Improved Understanding through
Data Integration,*** 2000***,*** EOS 81, 349, 354-355.

Lunar Exploration Science Working Group (LExSWG), ***Planetary Science
Strategy for the Moon***, July 1992, JSC document JSC-25920, 26 pp.

Lunar Exploration Science Working Group (LExSWG), ***Lunar Surface
Exploration Strategy***, Final Report, February, 1995, 50 pp.

Mars Exploration Program Analysis Group (MEPAG) Goals Committee,
***Scientific Goals, Objectives, Investigations, and Priorities***, July
16, 2004, Unpublished document, 23 pp.
<http://mepag.jpl.nasa.gov/reports/MEPAG_goals-3-15-04-FINAL.doc>

NASA Office of Space Science, ***Solar System Exploration***, 2003, 68
pp.

NAS National Research Council, ***New Frontiers in the Solar System: An
Integrated Exploration Strategy***, 2003, 248 pp.

Rao, M.N., D.H. Garrison, D.D. Bogard, and R.C. Reedy, ***Determination
of the flux and energy distribution of energetic solar protons in the
past 2 Myr using lunar rock 68815***, Geochim. Cosmochim. Acta 19,
pp.4231-4245, 1994.

Shearer, C.K. and Papike, J.J., ***Magmatic evolution of the Moon,***
1999, Amer. Mineral. 84, 1469-1494.

**APPENDIX I**

**CHARTER**

**Mars-Moon Science Linkages (MMSL) Science Steering Group**

[Request from NASA HQ]{.underline}

Given the recently announced presidential vision for exploration of the
Moon and Mars, NASA HQ formally requests that MEPAG consider how to
define the science-based activities on the lunar surface that would
benefit the scientific exploration of Mars. This analysis will need to
be derived from multiple approaches:

-   Evaluate how MEPAG 's scientific objectives for Mars (and their
    derivative investigations and measurements) could be enhanced by a
    first application on the Moon.

-   Determine whether demonstrations of engineering capability at the
    Moon could have significant feed forward to the Mars scientific
    exploration program.

-   Determine whether any of the primary scientific exploration goals
    and objectives for the Moon are linked to the goals and objectives
    for Mars.

[Starting assumptions]{.underline}

1.  Assume scientific priorities for the exploration of Mars are
    described in the MEPAG Goals document
    (<http://mepag.jpl.nasa.gov/reports/MEPAG_goals-3-15-04-FINAL.doc>).

2.  The most current reference material for lunar science can be found
    at <http://www.lpi.usra.edu/lunar_return/>.

3.  Assume a Lunar Reconnaissance Orbiter (LRO) mission to the Moon in
    2008, a robotic landed mission by 2010, and a TBD schedule of
    robotic lunar missions (perhaps on an annual basis?) until a first
    human return to the lunar surface in 2020. Results from any given
    lunar mission can influence a martian mission scheduled 6-7 years
    later.

4.  Return to the Moon is motivated by its use as a test-bed for human
    exploration of Mars, which must encompass science, utilization of
    accessible resources, operational scenarios involving humans
    interacting with robotic systems, and technology demonstrations of
    direct benefit to planned activities on Mars.

5.  This SSG is asked to focus its effort on martian and lunar surface
    science, rather than orbital science. This is because of the
    assumption that eventual human missions to Mars will go to the
    martian surface, and the assumption that orbital science has
    recently been sufficiently defined for current purposes through the
    recent planning for 2005 MRO and 2008 LRO.

[Requested Tasks:]{.underline}

1.  Develop a quantitative analysis of the [potential]{.underline} ways
    in which the scientific objectives for the exploration of Mars can
    be advanced through any of the following activities:

    a.  Scientific investigations on the Moon

    b.  Demonstrations of science-related hardware, including
        instruments, science tools, and/or sample preparation systems

    c.  Demonstrations related to spacecraft operations.

> Traceability of these possibilities to the objectives described in the
> MEPAG Goals document is essential.

2.  Develop an assessment of the [priority]{.underline} of the
    possibilities outlined in Task #1. Prioritization criteria should
    include:

    a.  Degree of alignment with MEPAG's priority system for Mars
        exploration.

    b.  Degree of criticality of the possible lunar activity to one or
        more future Mars missions (or surface measurement activities)

    c.  Intrinsic scientific value (for both Mars and the Moon).

    d.  Feasibility within the emerging strategy for precursor robotic
        lunar missions in support of human exploration.

[Methods]{.underline}

-   SSG membership should include experts in both Mars and the Moon,
    with expertise in instrument investigations and sample analysis of
    both bodies.

-   The SSG is asked to conduct its business primarily by
    teleconferences, e-mail, and or web-based processes. In addition,
    there is adequate budget to convene 1 or 2 face-to-face meetings, as
    required.

-   Logistical support will be provided by the Mars Program Science
    Office at JPL.

-   The Mars-Moon SSG must be well coordinated with the Mars Human
    Precursor Testbed (MHPT) SSG, and there may be a need for dual
    membership on both SSG's for some colleagues.

[Timing]{.underline}

-   The SSG is asked to carry out its deliberations in two phases, and
    to start by mid-April, 2004.

-   Phase I. Scoping analysis. These results will be presented to MEPAG
    at its June 30-July 2, 2004 meeting, and that presentation will be
    the basis for a significant discussion. In preparation for this, a
    draft report should be presented to the MEPAG Executive Committee no
    later than two weeks before the MEPAG meeting.

-   Phase II. Refined analysis. Details to be defined based on results
    from Phase I and input received at the mepag meeting.

-   Assume for planning purposes that the final report of the SSG needs
    to be completed within 2-3 months of the MEPAG meeting.

-   NASA HQ is forming a lunar science planning team parallel to that of
    MEPAG, under the working name of LEPAG. LEPAG may jointly sponsor
    this activity.  When LEPAG comes into existence, we plan to
    reconsider the charter, add any additional elements needed by LEPAG,
    add a few more members, and let the effort continue.

[Report Format]{.underline}

-   It is requested that the results of this analysis be presented in
    the form of both a Powerpoint presentation and a white paper.
    Additional supporting documents can be prepared as needed. After the
    white paper has been accepted by program management (including the
    MEPAG executive committee), it will be posted on a publicly
    accessible web site.

-   The report should not include any material which is a concern for
    ITAR (as is true of everything done by MEPAG).

APPENDIX II

Linkages between Lunar Investigations and MEPAG Goals

+-----------------------------------+-----------------------------------+
| **Lunar Science Investigations**  | **Linkage to MEPAG (2003) Goals** |
|                                   |                                   |
|                                   | **Goal-Objective-Investigation**  |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| Structure and Composition of      | Goal II, Objective B,             |
| Planetary Interiors               | Investigations 3                  |
|                                   |                                   |
|                                   | Goal III, Objective B,            |
|                                   | Investigations 1,2,3              |
+-----------------------------------+-----------------------------------+
| Planetary Differentiation         | Goal II, Objective B,             |
|                                   | Investigations 3                  |
|                                   |                                   |
|                                   | Goal III, Objective B,            |
|                                   | Investigations 1,2,3              |
+-----------------------------------+-----------------------------------+
| Thermal & magmatic Evolution      | Goal I, Objective C,              |
|                                   | Investigation 2                   |
|                                   |                                   |
|                                   | Goal III, Objective A,            |
|                                   | Investigation 4                   |
|                                   |                                   |
|                                   | Goal III, Objective B,            |
|                                   | Investigations 1,2,3              |
+-----------------------------------+-----------------------------------+
| Origin and History of Exogenous   | Goal I, Objective A,              |
| Volatiles                         | Investigation 1,2,3               |
|                                   |                                   |
|                                   | Goal I, Objective B,              |
|                                   | Investigation 1,2,3               |
|                                   |                                   |
|                                   | Goal II, Objective A,             |
|                                   | Investigation 1                   |
|                                   |                                   |
|                                   | Goal II, Objective B,             |
|                                   | Investigations 3                  |
|                                   |                                   |
|                                   | Goal III, Objective A,            |
|                                   | Investigation 5                   |
+-----------------------------------+-----------------------------------+
| Impactor Flux vs. Time            | Goal II, Objective B,             |
|                                   | Investigations 3                  |
|                                   |                                   |
|                                   | Goal III, Objective A,            |
|                                   | Investigations 3, 4, 11           |
+-----------------------------------+-----------------------------------+
| Planetary Asymmetry               | Goal III, Objective B,            |
|                                   | Investigations 1,2,3              |
+-----------------------------------+-----------------------------------+
| Regolith                          | Goal II, Objective B,             |
|                                   | Investigations 3                  |
|                                   |                                   |
|                                   | Goal III, Objective A,            |
|                                   | Investigation 9                   |
+-----------------------------------+-----------------------------------+
| Interpreting Geologic             | Goal III, Objective A,            |
| Environments                      | Investigations 4,9                |
|                                   |                                   |
|                                   | Goal III, Objective B,            |
|                                   | Investigation 3                   |
+-----------------------------------+-----------------------------------+
| Energetic Particle History        | Goal I, Objective A,              |
|                                   | Investigation 3                   |
|                                   |                                   |
|                                   | Goal I, Objective B,              |
|                                   | Investigation 2                   |
|                                   |                                   |
|                                   | Goal I, Objective C,              |
|                                   | Investigation 3                   |
|                                   |                                   |
|                                   | Goal II, Objective B,             |
|                                   | Investigation 2                   |
+-----------------------------------+-----------------------------------+
| Origin and History of Endogenic   | Goal I, Objective A,              |
| Volatiles                         | Investigation 2                   |
|                                   |                                   |
|                                   | Goal I, Objective B,              |
|                                   | Investigation 2,3                 |
|                                   |                                   |
|                                   | Goal II, Objective A,             |
|                                   | Investigation 1                   |
|                                   |                                   |
|                                   | Goal II, Objective B,             |
|                                   | Investigations 3                  |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| Water as a Resource               | Goal IV, Objective B,             |
|                                   | Investigations 8,9                |
+-----------------------------------+-----------------------------------+
| In situ Fuel Sources              | Goal IV, Objective B,             |
|                                   | Investigation 7                   |
+-----------------------------------+-----------------------------------+
| Exploration and Processing of     | Goal IV, Objective B,             |
| Planetary Materials               | Investigations 8,9, 10            |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+
| Communication & Ranging Systems   | Goals I,II, III, IV               |
+-----------------------------------+-----------------------------------+
| Drilling Technologies             | Goal IV, Objective B,             |
|                                   | Investigations 9                  |
+-----------------------------------+-----------------------------------+
| Life Detection & Planetary        | Goal I                            |
| Protection                        |                                   |
+-----------------------------------+-----------------------------------+
| ISRU Technology Demonstrations    | Goal IV, Objective B,             |
|                                   | Investigations 9                  |
+-----------------------------------+-----------------------------------+
| Sample Selection and              | Goals I,II, III, IV               |
| characterization                  |                                   |
+-----------------------------------+-----------------------------------+
| Sample Return Technologies        | Goals I,II, III, IV               |
+-----------------------------------+-----------------------------------+
| Seismic Net Technologies          | Goal III, Objective B,            |
|                                   | Investigations 1,2,3              |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+

APPENDIX III

Comparison between priorities to Mars science and lunar science for
Category A.

APPENDIX IV

Comparison between priorities to Mars science and lunar science for
Categories B and C.

# APPENDIX V

Examples of "AO-style\" writeups for select major lunar science themes

# 

# **Investigation A2. Origin and History of Exogenic Volatiles**

***- Objective:***

Identify, characterize, and quantify near-surface exogenic volatiles in
lunar polar

regions

***- Investigations:***

\(a\) Confirm the presence of volatiles in the upper regolith

\(b\) Determine and quantify their spatial distribution in 3-D so as to

evaluate their cosmic history and economic significance

\(c\) Characterize their elemental composition, concentration, physical

and chemical state

***- Measurements:***

\(a\) Active sounding of the upper X m of regolith to determine the
presence of volatiles in cryogenic traps (radar)

\(b\) Characterize thermal properties of regolith at XX km spatial
resolution (heat low probes and thermal IR)

\(c\) Determine surface morphological effects of volatile
condensation/sublimation cycles (high-resolution radar imaging)

\(d\) Characterize mechanical properties (landers and penetrators)

\(e\) Determine the elemental composition of surface volatiles (neutron,
gamma rays)

\(f\) Determine molecular composition and distribution (soil heating
experiments)

**Investigation A3. Decipher Planetary Thermal and Magmatic Evolution**

***- Objective:***

Characterize the thermal and magmatic history of the Moon

***- Investigation(s):***

\(a\) Characterize the volume of erupted volcanic material as a function
of time

\(b\) Characterize the global lunar heat flow

\(c\) Characterize the interior density structure of the Moon

***- Measurements:***

\(a\) Determine the depth of mare basalts across the Moon to XX m
vertical

accuracy at XX km spatial resolution (e.g., radar sounding or seismic
profiling)

\(b\) Measure the surface heat flow of the Moon to XX W/m2 accuracy on
spatial scales no coarser than XX km (e.g., heat flow penetrators)

\(c\) Determine the depth of crust, mantle, and core layers to XX km
accuracy on

spatial scales no coarser than XX km (e.g., global seismic network)

**Investigation A1. Impactor Flux versus Time**

***- Objective:***

Determine the size-frequency distribution and time variability of the
impactor

population in the Earth-Moon system.

***- Investigations:***

\(a\) Characterize the ages of lunar basins \>XX km in diameter

(b) Characterize the small impactor population within the past XX b.y.

***- Measurements:***

> \(a\) Returned lunar samples, or in situ age dating, adequate to
> provide age dates for major basins.
>
> \(b\) Returned lunar samples, or in situ age dating, adequate to
> constrain ages of mare basalt units larger than XX km^2^ in extent.

**Investigation A5. Characterize the structure and composition of
planetary regoliths**

***- Objectives:***

> Determine the process of regolith formation and subsequent
> modification.
>
> Determine the inventory of potential regolith resources, including
> volatiles.

***- Investigation(s):***

\(a\) Characterize the vertical structure of the lunar regolith, and its
variability between mare and highland provinces.

\(b\) Characterize the distribution of lunar resources on horizontal
scales of XX km.

***- Measurements:***

> \(a\) Orbital regolith probing by long-wavelength imaging radar;
> shallow seismic or electrical studies; drilling to depths of at least
> 10 m.
>
> \(b\) IR spectroscopy, radar probing for mineral mapping; orbital and
> in situ measurements of volatiles (neutron, gamma-ray, mass
> spectroscopy).