# Presentation: 252030

## PLANETARY CHRONOLOGYImportance for Mars

**Report to MEPAG, Washington, DC,**
**January 9-10, 2007**
**Nadine G. Barlow**
**Northern Arizona University**

## Workshop on Surface Ages & Histories: Issues in Planetary ChronologyHouston May 21-23, 2006

**Result:  Formation of ad hoc Committee on Planetary Chronology**
- P Schenk, N Barlow, B Bierhaus
- D Bogard, W. Bottke, W Hartmann, H Levison, A McEwen, W McKinnon, F Nimmo, C Quantin, K Tanaka, E Turtle, and growing . . .
**Result: Preparation of a White Paper-style report on “Planetary Chronology 2007: Status and Issues” for peer-reviewed journal **
**Result:  Preparation of Set of Recommendations for improving understanding of surface ages & chronologies in Solar System**

## Recommendations for Improving Understanding of Surface Ages & Chronologies in Solar System

***3 Major Chronology Themes***
*** ***
**Radiometric Dating of Samples**
**Crater-Based Chronologies**
**Solar System Dynamics**

## Recommendations for Improving Understanding of Surface Ages & Chronologies in Solar System

***-  RADIOMETRIC DATING OF SAMPLES  -***
***Objective A1:  *****Firmly anchor Lunar Time Scale, both currently & at  LHB**
***Recommendation A1:  *****We recommend that new samples be acquired from lunar surface, with priority to Copernicus and pre-Imbrium basin (e.g., Nectaris, SP-Aiken)**
***Objective A2:  *****Firmly establish Impact-derived Chronologies on another body**
***Recommendation A2:  *****We recommend that geologically-interesting samples be acquired from the surface of another celestial body beyond the Earth-Moon system (*****i.e., Mars*****)**

## Recommendations for Improving Understanding of Surface Ages & Chronologies in Solar System

***-  CRATER COUNTING (1)  -***
***Objective B1:  *****Achieve transparency in crater count statistics & age estimates**
***Recommendation B1:  *****We recommend that all crater statistics and support data (e.g., marked maps showing crater locations) be published on-line in a consistent style and level of detail**
***Objective B2:  *****Understand the consistency and reliability of crater statistics (especially the SFD) as an age dating tool**
***Recommendation B2a:  *****We recommend studies to evaluate the degree of human variability in crater measurement**
***Recommendation B2b:  *****. . . that in select locales that craters be counted by two or more independent  groups**
***Recommendation B2c:  . . .***** automating the crater counting process as completely as is practical**

## Recommendations for Improving Understanding of Surface Ages & Chronologies in Solar System

***-  CRATER COUNTING (2)  -***
***Objective B3: ***** Understand contribution of secondary craters to production function**
***Recommendation B3a:*****  We recommend that numerical modeling and geologic mapping to evaluate SFD & mass-velocity relationships for secondary craters **
***Recommendation B3b:*****  We recommend Monte Carlo simulations of terrains to investigate the effects of secondary crater formation on local terrains**
***Objective B4: ***** Understand the Lunar Production Function**
**Recommendation B4:  We recommend numerical modeling and geologic mapping to evaluate the SFD and mass-velocity relationships**

## Recommendations for Improving Understanding of Surface Ages & Chronologies in Solar System

***-  DYNAMICAL MODELING  -***
**Modeling of Giant Planet/Small Body dynamics by Bottke, Levison, et al. suggests LHB Dynamical Link in both Inner & Outer Solar Systems!**
***Objective C1:  *****Understand the orbits and size distributions of impactor populations throughout the solar system as a function of time and location**
***Recommendation C1a: ***** We recommend continued study of solar system dynamics, especially small-body dynamics **
***Recommendation C1b: *****  We recommend continued study on the collisional evolution of asteroidal and cometary bodies over time**

## Planetary Chronology 2007: Status, Issues, and Recommendations

**Emerging Consensus that Synergy of Radiometric Dating, Crater Counting, and Dynamics is Key**
***Dynamical modeling may finally link cratering records in ISS and OSS!***
**Report to Peer Journal (MAPS, JGR) in preparation (and will be posted on MEPAG website)**
***Recom’s not set in stone; Contributions from Community Welcome!***
***Establishing SS Chronology should be a NASA priority***
**Similar Chronology Summary Briefing was presented to OPAG and will be presented Thursday at VEXAG**