NASA MEPAG Report: Science Analysis of the November 3, 2005 Version of the Draft Mars Exploration Program Plan

January 6, 2006

Prepared by the MEPAG ‘2005 Mars Program Plan Science Analysis Group’

• Ray Arvidson, Washington University in St. Louis, Chair
• Carlton Allen, NASA Johnson Space Center
• David DesMarais, NASA Ames Research Center
• John Grotzinger, California Institute of Technology
• Noel Hinners, Former NASA and aerospace industry executive
• Bruce Jakosky, University of Colorado
• John F. Mustard, Brown University
• Roger Phillips, Washington University in St. Louis
• Christopher Webster, Jet Propulsion Laboratory

Correspondence contacts: Dr. Ray Arvidson (senior author), arvidson@rsmail.wustl.edu, 314-935-5609, or Dr. David Beaty (MEPAG contact), David.Beaty@jpl.nasa.gov, 818-354-7968.

This report has been approved for public release by JPL Document Review Services (CL#06-0090), and may be freely circulated. Suggested bibliographic citation:

Arvidson, R.E., Allen, C.C., DesMarais, D.J., Grotzinger, J., Hinners, N., Jakosky, B., Mustard, J.F., Phillips, R., and Webster, C.R., (2006). Science Analysis of the November 3, 2005 Version of the Draft Mars Exploration Program Plan. Unpublished report dated Jan. 6, 2006, 13 p, posted January, 2006 by the Mars Exploration Program Analysis Group (MEPAG) at http://mepag.jpl.nasa.gov/reports/index.html.

1. Purpose and Scope:

The purpose of this report is to provide comments on the draft Mars Program Plan for the next decade. Specifically, comments are provided on the version of the plan presented during the MEPAG Meeting on November 3, 2005. These comments are authored by the Draft Program Plan Science Analysis Group (SAG). The SAG was chartered by MEPAG to consider the extensive discussion and input about the draft plan from the MEPAG attendees, together with analyses conducted by the SAG, and to provide a report that delineates the strengths and weaknesses of the draft plan, together with possible alternative approaches. Further, the SAG considered the overarching scientific themes for the next decade of Mars exploration and the technological infrastructure needed to implement the plan and viable alternatives.

This report first considers the overarching goal and objectives that the SAG believes are crucial for a sustained program that will engage the public and address important scientific questions. A summary of the draft program plan is then presented in light of the goal and objectives, followed by detailed analyses of the plan. The SAG notes that its main role was to define issues with and alternatives to the plan, without recommending a specific implementation approach. The SAG does make specific comments about its preferences as appropriate in this report.

2. SAG Membership

Membership for the SAG is listed below and was chosen to ensure both breadth of understanding of Mars and important science questions, together with depth in particular aspects of Mars missions and scientific disciplines:

• Ray Arvidson, Washington University in St. Louis, Chair
• Carlton Allen, NASA Johnson Space Center
• David DesMarais, NASA Ames Research Center
• John Grotzinger, California Institute of Technology
• Noel Hinners, Former NASA and aerospace industry executive
• Bruce Jakosky, University of Colordao
• John Mustard, Brown University
• Roger Phillips, Washington University in St. Louis
• Christopher Webster, Jet Propulsion Laboratory

In addition, Dave Beatty, Jet Propulsion Laboratory, organized telecons and participated in discussions.

3. Program Scientific Goal and Objectives:

After extensive discussion within the SAG, and consideration of comments made during the November 2005 MEPAG Meeting, the following broad scientific goal and associated objectives emerged as ones that are judged to be scientifically of highest importance and that will provide a high level of interest to the various stake-holders involved in Mars exploration (scientific community, Congress and Executive Branches of government, public):

Program Goal: “Understand the evolution of Mars, the presence or absence of habitable zones, and if life formed or existed.” This approach will allow us to understand how tectonic (internal and via impact) and climatic processes led to past and current conditions on Mars and how these processes may have generated habitable zones and life. Following this goal will also maximize our understanding of how planets evolve over time and how the evolution of Mars compares to the evolution of the other terrestrial planets, including Earth.

Objectives for the Next Decade: “Follow the Water and Search for Habitable Zones.” These objectives will focus a search for habitable zones as part of the overall goal of understanding Mars as a system and how that system led may have led to formation of habitable zones for supporting life.

The SAG believes that each mission that is part of the program plan should be judged against how the investigations would help meet the goal and objectives listed above.

4. Overview of Draft Program Plan

The draft plan presented during the MEPAG Meeting included the following set of missions and associated investigations, with a timeline that extended over ~15 years. The extended timeline is a consequence of budgetary limitations.

• 2011/2013 Scout and core science orbiter with telecommunications capability
• 2016 Mid-rovers or Astrobiology Field Laboratory
• 2018 Scout
• 2020 Planetary Evolution and Meteorology Network
• 2022 Mars Sample Return Orbiter with Telecom
• 2024 Mobile Mars Sample Return

There are four core science investigations expressed in the plan, in addition to the use of Scouts to enhance the core program. The four core investigations are listed below, together with the SAG’s view of the most important measurements and/or approaches that should be associated with each of the core investigations. The core investigations map directly into the missions listed above.

• 2011/2013: Determine: (a) atmospheric escape rates for key species, and (b) the detailed composition, abundance, and distribution of atmospheric trace gases (e.g., for methane).
• 2016: Determine if there were or are habitable zones and life, and how their development was related to the overall evolution of the planet, through surface observations using rover-based systems that acquire and analyze samples.
• 2020: Determine the structure and dynamics of the interior using seismic and heat flow measurements since these measurements are fundamental to understanding Mars as a system.
• 2022/2024: Return samples using rover-based collection systems in locations for which Earth-based sample analyses would maximize understanding of the evolution of the planet, habitable zones, and whether or not life developed or existed on Mars.

5. Analyses of the Draft Program Plan

Based on comments on the draft plan made by community members during the MEPAG Meeting, and its own analyses, the SAG determined that the draft program plan overall approach, with its four core science investigations, augmented by Scouts, is a scientifically robust plan that will meet the program goal and objectives. Key issues are the relative timing of the missions (i.e., how to decide on a particular temporal implementation of the plan), the role of Scouts, and consideration of the infrastructure (particularly technology readiness for specific missions, together with telecommunication systems) needed to implement the draft plan.

5.1 Comments on the Draft Program Plan Through 2013

The SAG felt that the combination of a Scout and a core orbiter mission for the 2011/2013 opportunities represented a reasonable approach consistent with expected budget profiles and technological readiness issues. A core orbiter mission during the 2011/2013 opportunity would add a great deal of information about the loss of atmospheric species to space and/or determination of the nature, abundance, fluxes, and source locations for trace species. These atmospheric measurements are fundamental for understanding the evolution of the atmosphere, climate, and the presence of habitable zones.

A concern associated with the 2011/2013 opportunity is the manner by which potential conflicts between core orbiter and Scout missions will be managed. Definition of both programs is ongoing at present and, in fact, the order of the two missions for 2011 or 2013 has not yet been decided. The core orbiter “strawman” investigations are in the process of being defined by a core orbiter science SAG, which has been assembled and is expected to complete its report within several months. The Scout Announcement of Opportunity for the 2011/2013 mission will also be released within the next several months, although numerous Scout teams are already deeply involved in the proposal generation process. The best strategy, both from programmatic and scientific perspectives, is for planning for the two missions to proceed in parallel, with the selection of the science thrust for the earlier mission clearly impacting the science thrust that will be selected for the later one. This approach provides maximum scientific and programmatic flexibility, without unduly hindering likely proposers for either mission.

5.2 Comments on the 2016 Opportunity

The SAG spent most of its deliberations focused on the 2016 mission opportunity and debating whether the appropriate mission should be continued in-situ exploration of the surface and/or subsurface, a sample return mission, or implementation of a network of surface stations to conduct seismic, heat flow, and atmospheric observations. All three missions would meet the program goal and objectives. In the paragraphs below we present arguments associated with keeping in-situ observations in the 2016 time slot, as opposed to swapping in the: (a) Mars sample return mission (2016/2018) and (b) network science mission. The report also lists implications for technology development and other infrastructure issues associated with various alternatives for the 2016 opportunity. We note that during the November 2005 MEPAG Meeting and during the SAG telecons the issue of which mission to fly in 2016 caused the most heated discussions.

5.2.1 Surface-Based In-situ Investigations

The draft plan includes a rover-based mission with in-situ investigations for the 2016 opportunity. Given the likely budget profile, this may be one large rover, such as the Astrobiology Field Laboratory (AFL), or two mid-range rovers with the capability to make both remote sensing and in-situ observations, but without the extensive analytical laboratories aboard the planned for AFL. AFL would be a natural follow-on to MSL, providing a long-lived rover with remote sensing and in-situ laboratory capabilities to explore regions and materials thought to have supported habitable zones. The mid-range rovers would investigate the geologic evolution and biological potential of multiple locations on Mars where orbital data show the presence of aqueous minerals and thus a history involving water. In particular, mobile rovers provide by far the most effective means to distinguish between the rock types that are most likely to preserve evidence of life, for example chemically precipitated sedimentary rocks. Mid-range rovers might have a Mars Exploration Rover (MER) Athena-like payload [1] with remote sensing and contact in-situ measurements, with some capability to detect reduced carbon compounds, (e.g. Raman Spectroscopy). The two MER rovers have traversed over a dozen kilometers and have clearly demonstrated the need for lateral mobility to find key rocks and soils for analyses and to place results in geologic context. Thus the SAG strongly endorses the need for rover capabilities for the in-situ mission for the next decade and would reject any suggestion that the 2016 in-situ opportunity focus instead on measurements from a static lander only.

There are compelling science and exploration rationales for implementing a rover mission or missions and associated in-situ observations during the 2016 opportunity.

• MER [2,3] and recent orbital [4,5] observations show that the Martian crust is surprisingly diverse in composition, structure and in the variety of aqueous processes that have modified it over time. These discoveries greatly expand the number of compelling sites relevant to the search for evidence of habitability and life and to understand climate and geological history.
• A rover-based in-situ mission would extend to new sites the detailed characterization of surfaces and materials for ground-truth calibration of orbital data. Prior surface missions have demonstrated that ground truth data are critical to calibrate orbital observations. Therefore the accuracy of orbital observations of the diverse martian crust depends critically upon surface observations conducted at diverse sites.
• Results of the 2007 Phoenix Lander (e.g., TEGA-based evolved gas analysis) and Mars Reconnaissance Orbiter (MRO) observations (e.g., targeted HiRISE, CRISM, and CTX for ~1000 sites) would be available to guide site and instrument selection. Initial results would also be available from the 2009 MSL mission to help guide selections, although the SAG expresses concern that MSL results may not be available in time to guide instrument selection for a 2016 opportunity.
• Evidence of life and ancient climates would reside in certain rock types and mineral phases (e.g., silica, phosphates, carbonates) that can most effectively preserve such evidence. In many cases these materials can only be located during a surface mission with significant mobility and on-site measurement capability. The 2016 rover mission is perhaps the most effective means for discovering samples that preserve records of life and climate and thereby would optimize the probability of sending a later MSR mission to a location that maximizes the probability of collecting samples of direct relevance to habitability and life.
• It can be argued that the cycle of orbital and landed observations of the martian crust is the “engine” that drives discovery in multiple disciplines in Mars science and that addresses the search for direct evidence of life, ancient climates, and the compositional and structural evolution of the martian crust. The 2016 Mars rover mission is in many ways the keystone that can sustain these multiple lines of inquiry during the next decade.

One issue raised during the MEPAG Meeting was that cosmic rays and their spallation products over the aeons may have caused organic compounds to convert to graphite for deposits that have remained within the top meter from the surface. Therefore drilling to depths beyond a meter was suggested to ensure access to any organic materials. The contention that organic material within a meter of the surface would be destroyed needs quantification, both the process and the timescale. Further study is also needed to understand the extent to which surfaces have remained static for aeons. Certainly MER and orbital observations show extensive burial and erosion by wind, water, and volcanism at many locations and scales. Lateral mobility conceivably could access materials that have been exhumed relatively recently from depths >1m. The SAG also notes that the requirement for vertical mobility to access unprocessed carbon compounds will be better understood following the results from the evolved gas analyzer (TEGA) that is part of the payload on the 2007 Phoenix Lander mission. MSL results will also provide direct information on the depth distribution of reduced carbon compounds. The SAG’s opinion is that lateral mobility, with AFL or mid-range rovers, is more important for the 2016 opportunity than extensive vertical mobility (i.e., > 1 m).

The SAG considered scientific results that would lead to a selection of an AFL or a pair of mid-range rovers for the 2016 opportunity. It is the opinion of the SAG that either mission approach would be scientifically compelling and consistent with the program goal and objectives. The AFL selection was judged to more directly address habitability and life and would be preferred if the combination of existing data (e.g., MGS, Odyssey, MEx, MER), coupled with data expected from MRO and Phoenix, lead us to suspect that there are key areas where evidence for habitable zones and perhaps life are best preserved. MSL results may be available too late in the rover development cycle to impact whether an AFL or mid-range rover is the appropriate choice. It is noted that technology development for AFL will benefit greatly from MSL development efforts. Development of mid-range rovers represents a new line, based only partly on MER. Careful consideration must be given to the timing of a decision for an AFL or mid-range rover mission in 2016 to ensure enough development and testing time for the selected vehicle.

The SAG notes that technology investment in in-situ instruments is critical and may not be happening at the rate it should to support a 2016 rover-based mission. It is noted that MEPAG, during its April 2006 Meeting, plans on addressing from an end to end perspective the development of instrumentation needed to implement the draft program plan and viable alternatives.

Finally, the SAG notes that the European Space Agency (ESA) has initiated detailed planning for its ExoMars rover mission, with measurement capabilities similar to what one might envision would be included on an AFL. The SAG’s opinion is that collaboration with ESA might make an AFL-like mission happen during the 2016 opportunity (or earlier) and perhaps allow earlier implementation of sample return or network science elements of the draft program plan.

5.2.2 Swapping in Sample Return

The value of a Mars Sample Return (MSR) Mission and Earth-based analyses of samples is summarized below as part of an alternative plan that includes MSR in 2016/2018. The SAG notes that The National Research Council Decadal Survey for Solar System Exploration considered MSR to be so important that it was ranked as the highest priority for a large (>$650 million) Mars mission in the next decade [6].

• The resolution and range of analyses available in terrestrial labs will be much better than anything we will be able to fly in the foreseeable future. Further, as instruments improve and understanding evolves, the samples are in hand to support new discoveries. For example, a major conclusion about early lunar evolution was announced in November, 2005 based on new techniques of Hf-W (Hafnium-Tungsten) chronology – some 30 years after Apollo returned the samples. In a real sense, each new analysis performed on returned samples may be viewed as an equivalent to a new in-situ measurement performed on Mars, but at much less cost and much greater frequency.
• The samples will serve as ground truth for the huge volumes of remote sensing and in-situ data that have been and will be obtained. For example, Mars Exploration Rover (via Moessbauer Spectrometry) and Mars Express OMEGA (via reflectance spectrometry) data [3,4] indicate the presence of hydrated iron and magnesium sulfates in layered sedimentary deposits. These results have had a significant impact on our understanding of the aqueous history of Mars. These crucial mineral identifications can be confirmed or refuted unequivocally within days based on analyses of carefully-selected returned samples.
• Unequivocal identification of evidence for life and habitability may require returned samples and exhaustive terrestrial analysis. For example, isotopic analysis of nanoparticles of carbon, indicative of origin, can be done only in terrestrial labs.
• Potential international partners, including ESA, are now considering incorporating sample return into their mission plans. Buoyed by the recent success of Mars Express, they realize the great scientific potential and that they have the technical ability to do the mission. MSR is an important, yet costly and technically challenging mission. This mission is perhaps best implemented as a joint NASA/ESA activity, thereby sharing the cost and technology development.
• An MSR mission directly supports the eventual human exploration of Mars. Results from sample return will provide science and engineering data not readily obtainable by remote sensing or in-situ analysis (see MEPAG Goals document). It further demonstrates “proof-of-concept” and learning relevant to the round-trip essential for human exploration of Mars. Similarly, it can provide the model for how to conduct in international human Mars exploration program. An MSR mission in the 2016/2018 opportunity will provide the public with a tangible demonstration that the United States is taking steps towards human exploration beyond the moon.
• Results from the first sample return mission will affect the course of the subsequent flight program. The detailed analyses will, as did Apollo sample analyses, provide guidance to instrument development and future surface in-situ investigations.

A sample return site could be selected using existing data (i.e., from MGS, Odyssey, MEx, MER data), although observations from MRO and MSL will provide valuable information needed to maximize the probability of choosing a site that will provide information about habitability and perhaps life. Results from Phoenix, MRO (and initial results from MSL) will be available in time to provide additional data for landing site selection.

A simple grab sample obtained from a stationary lander is judged by the SAG to be inadequate. The MER mission demonstrated the value of acquiring a range of samples from various localities within a given landing site. Thus a rover-based mobility system must be a fundamental aspect of MSR, either to collect samples and return them for ascent, or to return to a site where samples have been cached during a previous mission.

Cost and the reliability of cost estimates for MSR were two issues discussed at great length during the MEPAG Meeting and by the SAG. The history of recent MSR cost-estimation is as follows: NASA contracted with four industry groups (Ball Aerospace, Boeing, Lockheed-Martin, and TRW) in 2000 to independently design and estimate the costs for an MSR, with a nominal launch date of 2011. The reports were completed in 2001 and delivered to NASA. Although differing in details, all of the original mission designs include a rover with extensive on-board science instrument packages. Most of the designs mitigate mission risk by some level of redundancy of landers, launches, or both. As proposed, cost estimates for the original industry designs approach $3 billion in real year dollars. When normalized to single-launch/single-lander configurations, the industry designs have estimated costs in the range $1.3 B to $2.0 billion (FY02 dollars) [7,8]. SAIC and Aerospace Corporation both performed independent cost estimates on a non-mobility version of each of the team’s designs, as well as JPL’s internal design, and confirmed the validity of their costs. Additional work has been ongoing at JPL to determine the full costs of MSR. The current mission design included separate launches of an orbiter and a lander, a sample-collecting rover with a range of 1 km, and no in-situ science. The study also estimated the costs of a technology program (defined by a 2004 multi-center MSR Technology Board), operations, and post-return sample handling. Three industry groups independently provided NASA with design concepts and costs for a Sample Receiving Facility. The mission, featuring an initial launch in 2016 and sample return in 2018, was estimated to cost $3.3 billion real-year dollars [9]. The SAG concludes that costs are fairly well understood and that cost uncertainty should not be an impediment for a 2016/2018 MSR mission. .

A key issue associated with implementing an MSR Mission in 2016/2018 is technological readiness. A recent JPL study [9] defined the mission elements which require technology development, commencing in FY08, at the latest, to support a launch in 2016/2018:

• Parachute Development
• Pinpoint Landing
• Forward Planetary Protection
• Sample Containment
• Sample Acquisition
• Mars Ascent Vehicle
• Orbital Detection, Rendezvous and Capture
• Earth Entry Vehicle
• Sample Receiving

Technology development programs in direct support of an MSR mission have been ongoing for several years. The Mars Program Office Base Technology and Focused Technology Programs directed to the MSR flight segment has resulted in design concepts and prototype hardware for key mission components. This program was terminated in FY05. Three industry groups independently provided to NASA design concepts for a Sample Receiving Facility and identified key technology developments needed to be ready to receive and analyze samples. A companion program to develop key technologies for the Sample Receiving Facility has been designed, although not implemented. A separate program to develop technologies specific to Planetary Protection is ongoing. Technology development efforts must be reestablished as soon as possible and no later than FY08 to be able to meet a 2016/2018 MSR opportunity.

5.2.3 Swapping in Network Science

Network science focuses on study of the interior structure (seismology and heat flow), atmosphere and climate, made from multiple, simultaneous measurements on the Martian surface. The capabilities needed to deploy and operate multiple surface stations are substantial and require core mission funding to implement, i.e., they are beyond the capabilities that could be implemented with a Scout mission.

Seismic and heat flow measurements from carefully selected sites would provide fundamental information on the origin and subsequent evolution of Mars, its bulk composition, volcanic and tectonic history that drive the evolution of the atmosphere and water budget, the thermal state and history of the crust and mantle, the timing and character of the early dynamo and its possible role in pre-biotic chemistry. In particular, the existence of ancient (or contemporary) habitable zones depended (or depends), inter alia, on the thermal and crustal evolution of the planet. In analogy to the key measurements from an aeronomy mission (e.g. species escape rates), a geophysical network provides the boundary conditions on the role that the interior has played in enabling habitable environments. Additionally, regional variations in the thermal environment may modulate the locations and timing of habitable zone development and evolution.

An atmospheric network would provide diurnal and seasonal measurements of gases, water, dust, and fluxes, and thereby characterize the general circulation and climate for input to global models of Mars chemistry and dynamics, including horizontal and vertical transport. Ultimately, these parameters are critical for habitability and future human exploration. The SAG notes that for atmospheric science, more mission options exist as compared to implementing the seismic and heat flow investigations. As evidenced in earlier proposals, Mars Scout missions can accommodate multiple probes, penetrators, or ground stations devoted to atmospheric and climate studies. Also, Entry, Descent, and Landing phases of surface missions include acquisition of descent atmospheric profiles (e.g. Pathfinder and the Mars Exploration Rover Missions) that contribute to network atmospheric science. The SAG endorses the concept that each surface mission be considered part of an atmospheric network science “virtual” mission and include, to the extent possible, relevant atmospheric measurements.

There are two principal advantages of bringing the planned network science mission in 2016:

• We would in a more timely and direct way address one of the four core investigations, namely: “Determine the structure and dynamics of the interior using seismic and heat flow measurements.” Thus a geophysical evolutionary context for planetary habitability would be provided.
• Our European partners continue to express strong interest in network science, both geophysical and atmospheric, and it may prove an effective and cost-sharing partnership that would retain Scout funding for the following 2018 opportunity. ESA has formally endorsed geophysical and meteorological investigations as a high priority for Mars. They have included a GEP (Geophysical/Environmental Package) in the design of their ExoMars mission for 2011. In terms of the technological readiness, virtually all the European instruments are basically ready to fly now, and this could possibly form the basis for a NASA-ESA collaboration for a network mission.

Failing the inclusion of a network mission in the 2016 opportunity, the SAG believes that every effort should be made to include a seismometer on other landed missions in order to characterize the seismicity of Mars. The level of seismicity can be related to the present thermal state of the planet and would help refine the strategy for a future network mission. Inclusion of capabilities to measure heat flow should also be considered for landed missions.

5.3 Comments on the Role of Scout Missions

Scout Missions were discussed during the November 2005 MEPAG meeting and during SAG telecons and key results are summarized in this subsection. Through an open competition, Scout missions create opportunities for diverse, innovative, P.I.-led missions to be included in the Mars program. Such opportunities assist in building the community of future aerospace engineers and scientists. Scouts provide operational alternatives to core missions while still striving to achieve the key goals and objectives of the Mars program. This alternative mechanism potentially allows greater flexibility to respond relatively rapidly to discoveries and/or technological advances. And the lower cost of Scout missions, relative to core missions, helps to keep the Mars program within its budget while still utilizing each launch opportunity to achieve important science. Scout missions indeed offer operational and budgetary flexibility to the Mars Program, however they still should contribute directly to the key goals and objectives of the program.

The current cost cap imposed on Scout missions curtails many of the key advantages potentially offered by Scout missions. For example, many potentially valuable landed missions might no longer be financially viable. The current cost cap should be re-examined in light of anticipated costs of certain types of high-priority Scout mission concepts.

5.4 Comments on Program Telecommunications Infrastructure

The Mars Exploration Rover mission has clearly demonstrated the benefits of relay communications for support of Mars in situ exploration, including increased data return, reduced lander energy and mass requirements, provision of contact opportunities at a wide range of local times (thus increasing data return from the surface missions), and capture of high rate engineering telemetry during critical mission events such as Entry, Descent, and Landing. While current program budget constraints do not allow for inclusion of a dedicated Mars Telecommunications Orbiter, as had been originally planned in 2009, a strategy of periodic launch of long-lived science orbiters with telecommunications capability can sustain and grow the Mars relay infrastructure capabilities. To this end, the inclusion of an orbiter mission with telecommunications capability in either the 2011 or 2013 opportunity represents an appropriate implementation of that strategy. In addition, to ensure a robust infrastructure plan, the program should strive to maintain redundant on-orbit relay assets by managing the Odyssey and Mars Reconnaissance Orbiter spacecraft with the goal of significant extended lifetime. An alternative to the science/telecommunications orbiter implementation is inclusion in the Program Plan of one or more dedicated telecommunications orbiters. This may be necessary if orbits and mission concepts for the science portion of an orbiter mission compromise telecommunications capabilities during important surface operation periods.

6. Concluding Remarks

The program goal and objectives outlined above focus on understanding the evolution of Mars and whether or not habitable zones and life existed. This overarching approach will sustain an exciting and scientifically rich program of Mars exploration for the next decade and beyond. The draft program plan, with its four core science investigation themes, augmented by Scouts, is a scientifically sound and technologically viable approach for meeting the program goal and objectives. Scouts should remain an important component of the program to engage directly the community and implement missions that directly address the program goal and objectives in ways that complement the core investigations.

Technology development for instrumentation and missions is a key element of a successful program. Much needs to be done to ensure that these efforts are started early enough and funded well enough to enable the plan to be implemented on schedule.

Telecommunications capabilities are an integral part of what is needed to implement the plan and must be in place in time to support surface missions. These capabilities might be best implemented by including them on the core science orbiters planned for the next decade. If not, then alternatives need to be in the plan, including dedicated telecommunications capabilities.

Strong arguments can be made to have an AFL or mid-range rover mission in 2016, to swap in a rover-based sample return mission, and to swap in a network science mission. All of these choices address the program goal and objectives. We note that the selection of a particular mission will be based on science, cost, and political agendas. We also note that ESA is implementing its ExoMars rover in the next decade, with significant capabilities planned for determining aqueous history and habitability. ESA has, in the past, also considered network science missions to Mars. Both NASA and ESA have sample return as mission objectives in their plans. We strongly encourage NASA to consider international cooperation as a way of implementing the draft program plan in less than ~15 years that is currently envisioned. In fact we challenge the agency to implement the plan in a ~10 year time frame, including returning samples by 2020. Sharing mission costs via international participation will maximize our scientific return relative to investments in the program.

6. Acknowledgement

Chris Webster acknowledges support from the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

7. References

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