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> July 11, 2008

Dr. Michael Meyer, Mars Exploration Program Lead Scientist\
Planetary Science Division, Science Mission Directorate

NASA Headquarters

300 E Street SW

Washington, DC 20546

Dear Michael:

The purpose of this letter is to summarize the outcome and findings of
the recently concluded effort by the Mars Landing Site Steering
Committee to identify a new candidate landing site for the MSL
spacecraft. The intent was to review new data collected by MRO and other
spacecraft since the second workshop to ensure that new discoveries were
considered in the process of identifying candidate landing sites.

Four new sites were submitted for consideration following a call to the
Mars Landing Site Steering Committee, MRO PSG, and MSL PSG. These sites
included: South Meridiani Planum (3.3S ,354.4E), Chloride west of
Miyamoto Crater (3.1S, 351.6E,), Gale Crater (4.5S, 137.4E), and Nili
Fossae Carbonate (21.9N, 78.9E).

Following a two-week period to review the new sites, a telecon was held
to discuss them and to decide which would be added to the existing list
of candidate sites. The 25 participants represented the Steering
Committee, MSL PSG, NASA Headquarters, and individuals who had proposed
the sites. Following summary presentations of each site, any associated
safety concerns, and a discussion of the schedule and status of the site
selection process, the group began discussing the relative merits of the
new candidate sites.

There was unanimous agreement that all four of the new sites were
potentially equally or more compelling as the existing set of sites
under consideration. Moreover, the new South Meridiani site was deemed
to be as safe, but more scientifically compelling than the existing
North Meridiani site. Hence, there was near unanimous agreement that the
new South Meridiani site should be swapped for the existing North
Meridiani site.

There was considerable discussion of the other three sites as well, the
Gale Crater and Nili Carbonate sites in particular. Concern related to
the limited diversity of geologic targets at the Concern that the
Chloride site might offer only a limited diversity of geologic targets
was the main reason the site was not the favorite. Many participants
expressed concern that dropping either the Gale Crater or Nili Carbonate
Site without additional information (e.g., from HiRISE and CRISM) about
their potential setting and accessibility presented a science risk to
landing site selection. Most participants felt that both sites should
remain under consideration at least until the third landing site
workshop in September (new data from MRO is in the queue and will be
reviewed by the Committee in the coming few weeks to assess any new
discoveries). Nevertheless, the MSL Project and NASA Headquarters
specified the need to arrive at consensus on a single new site (in
addition to the South Meridiani site) and the group favored the Gale
Crater site by a two-to-one margin. The margin in favor of Gale Crater
was consistent for votes made by all meeting participants and votes by
only the Mars Landing Site Steering Committee members. Supporting
materials related to these new sites are posted at:
<http://marsoweb.nas.nasa.gov/landingsites/> and
<http://webgis.wr.usgs.gov/msl>).

We appreciate the opportunity for the science community to contribute to
the MSL landing site selection process. We hope that NASA will continue
to support analysis of potential future landing sites in order to
achieve the most comprehensive evaluation of their relative merits.

We stand ready to provide additional input to the process as requested.

Sincerely,

> ![](media/image2.jpeg){width="1.3340277777777778in"
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>
> John Grant
>
> ![](media/image3.jpeg){width="2.064583333333333in"
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>
> Matt Golombek

Co-Chairs, MSL Landing Site Steering Committee

On behalf of the MSL Landing Site Steering Committee