NASA MEPAG Report from the 2013 Mars Science Orbiter (MSO) Second Science Analysis Group
May 2007
Version 29 May 2007
Executive Summary
A scientifically bold orbital mission in 2013 can address profound and basic scientific gaps that remain in the era beyond MRO. Not surprisingly, there is no single instrument complement that addresses all of the highest priority science, and the science analysis group identified three primary mission scenarios that would address multiple objectives. The high priority measurements are each traceable to MEPAG and NRC goals. These measurements are directly linked to the requested science study areas of the Charter and other areas where critical gaps in current knowledge exist.
All three scenarios address a theme of Dynamic Mars: Activity, Transport and Change. Any one of these three scenarios will return significant new information relevant to our understanding of the planet, its history and its potential for life.
Plan A: Atmospheric Signatures and Near-Surface Change: This plan addresses the charter task to examine relatively short-lived atmospheric trace gases and follows up on discoveries of recent surface activity, such as new gullies. The intention is to provide a comprehensive characterization of the chemical composition of the Martian atmosphere, its global distribution and variation with season, with particular sensitivity for the ultra- low abundance species that might be signatures of subsurface processes related to existing habitable zones and possible life. The record of global climate measurements of atmospheric temperature, dust, water vapor, and surface albedo would be continued while providing new measurements, such as direct measurements of wind, that uniquely constrain and validate models of atmospheric dynamics and transport.
Plan P: Polar and Climate Processes: This plan approaches the orbital imaging and geophysics elements of the charter through the lens of the dynamics of volatile reservoirs and modern climate. This scenario follows up on discoveries of active erosion of the residual south CO2 ice cap and anticipated new results from the 2008 Phoenix polar lander. The focus is a detailed examination of the mass/energy balance through monitoring of both poles in space and time. Precise elevation and volume of seasonal and residual volatile deposits will allow a time variable measure of mass in exchange with the atmosphere and estimates of exchange with lower latitude volatile reservoirs at different epochs. The record of global climate measurements, particularly albedo and temperature relevant to energy balance, will be continued and new direct measurement of winds will improve models of surface-atmosphere interactions at all latitudes.
Plan G: Geological and Geophysical Exploration: This plan satisfies specific Charter requests to examine high-resolution imaging, orbital geophysics, and a landed geophysical package. The plan would follow up on discoveries such as the present-day (last decade) impact events and debris flows associated with gully activity. The first exploration of the uppermost few meters of regolith and mantling materials, and topographic change detection over broad regions is provided. The landed package would address high priority interior objectives such as seismic activity and structure of the crust, mantle and core, in addition to surface measurements of temperature, water vapor and dust electrification in the planetary boundary layer.
The SAG did not prioritize amongst the three scenarios, in that: No single scenario can complete the remaining significant orbital science to be accomplished in the wake of MRO. Each scenario addresses key (but different) MEPAG goals. All scenarios feed-forward to missions currently under study for 2016, 2018 and 2020 (e.g., Network, Sample Return, Astrobiology Field Lab, Mid-range Rovers) and to support of planning for human exploration, although each scenario has stronger ties to some missions than others.
Variations of these three thematic scenarios were then grouped into three tiers of mission science, based on completeness, synergy, and ROM costs:
Core Mission Concept (CMC): This level provides the best combination of investigations focusing on one of the above science scenarios while keeping key cross- disciplinary elements and staying within reasonably constrained resources of mass and cost.
Augmented: These scenarios added another complementary science thrust to the CMC. These options were in line with the MRO-class flight system capabilities but would require significantly increased funding and/or contributed elements to achieve the expanded suite of science objectives.
Reduced: This level is consistent with the nominal cost target provided by the project. However, the SAG judged these options to be much less desirable as they required significant compromises with regard to measurement goals or supported too few cross- disciplinary elements.
Findings:
The SAG strongly preferred the Core Mission Concepts over the reduced options, since the gain in science for the modest augmentation was very high and preserved the cutting-edge cross-disciplinary elements that are the hallmark of a core mission.
To this end, no single component should dominate the payload, and a landed element should not preclude significant, innovative orbiter science.
A single lander emphasizing geophysical measurements (including meteorology) is scientifically credible and could be paradigm-shifting. However, the notional lander system presented to the SAG appears to be inadequate in cost and mass.
The implementation required by each scenario is sufficiently different (e.g., orbital inclination or possible inclusion of a landed component) that it will require an early selection amongst the three scenarios.
International contributions could help with cost, but they (or their requirements) need to be carefully reviewed to ensure that key measurements will be met.
Programmatic Decisions Required Prior to the Science Definition Team (SDT)
- Is the drop-package to be a key component of the MSO mission?
- On which scenario should the SDT focus?
- What cost and mass resources will be baselined for MSO?
1 Background
In the winter of 2005/2006, a Science Analysis Group (SAG-1), chaired by C. B. Farmer was convened to examine the 2011/2013 launch opportunity. That group deliberated via telecon and email and delivered a final report in March of 2006 that analyzed science goals focused on the atmospheric evolution of Mars through study of the exosphere and atmospheric escape, and the composition and circulation of the lower atmosphere (available via the MEPAG web site http://mepag.jpl.nasa.gov/reports/MSO_SAG_report_071006.pdf). The primary measurements emphasized characterization of loss of water to space through the upper Mars atmosphere, complemented by measurements of key biogeochemical gases (particularly methane) in the lower Mars atmosphere, possibly identifying local areas for future landed exploration. The cost of mission, with straw-man payload, was included in 2006 POP guidelines and was carried over to 2007.
In January of 2007, two Mars Scout investigation teams, both focusing on the upper atmosphere processes and escape to space, were selected for a head-to-head competition for the 2011 launch opportunity. A new Science Analysis Group (SAG-2) was formed to re-evaluate scientific options for the 2013 launch opportunity. The Charter for the SAG-2 is provided as a preface to this document.
2 Deliberations/Process
Calvin agreed to Chair the SAG-2 in the latter part of January 2007. In consultation with the executive committee, Michael Meyer, Dave Beaty and Ray Arvidson, committee members were selected to address the specific scientific analysis requested in the Charter as well as span the breadth and diversity of Mars science under consideration. The group was under a rapid timeline to deliver a final report in 3.5 months in order to expedite the process through Science Definition Team (SDT) and Announcement of Opportunity (AO) with a desired release date in early 2008. The group met weekly by teleconference from Feb 7 to May 16, 2007 and 8 members of the SAG-2 met for a face-to-face meeting at the annual Lunar and Planetary Science Conference in March.
On average, each weekly telecon was attended by 13 of the 16 SAG members though participation in any given week varied. In March and April several additional Friday or Monday phone meetings were scheduled but with lighter attendance. Calvin distributed comprehensive written notes after each meeting so that those unable to attend would be up to speed with the conversation. In addition, a lively and extensive email exchange occurred, with between 15 and 50 emails traded each week on a variety of topics.
The initial meeting allowed the SAG-2 to discuss the Charter and basic mission constraints with the Executive committee and the Mars Science Orbiter (MSO) project office, represented by Tom Komarek and Daniel Winterhalter as the Study Scientist and liaison to the project. Early conversations outlined properties that should be representative of a program core mission (Section 3) as well as discussed overarching themes (Section 4) that are relevant given the wealth of new information and discovery in the past decade of Mars exploration. A comprehensive list of forward-thinking science goals was developed by the entire SAG-2
(Section 5). These goals incorporated the specific science analysis requests in the Charter. Given the emphasis on volatiles in the recent NRC decadal survey, an additional major set of goals in the area of polar processes emerged. In order to focus the dialog on the next critical measurements the SAG-2 was split into four sub-groups along discipline lines, where the key measurements were further refined (Section 6). High priority measurements were defined and strawman payload instruments were identified that can accomplish the measurement goals (Section 7). Numerous potential combinations of instruments were considered and the SAG-2 ultimately reduced these to three scenarios with science synergies, diverse feed-forward ability and within the evolving cost guidelines that were provided to the SAG-2. These scenarios are described in Section 8. The MSO project looked at one of these scenarios in light of mission implementation (Section 9), though specific mission trades will need to be explored in more detail by the SDT. In Section 10 we consider how these scenarios will support future (including human) exploration. Specific science issues that were discussed, some of which were resolved, and others not, is given in Section 11. We conclude (Section 12) that there is ample innovative science to be done in orbit at Mars.
3 Core MSO Mission Attributes
An outcome of early discussions was to classify properties that distinguish a core Mars Exploration Program (MEP) mission from competed Scouts and smaller focused objectives. The SAG-2 agreed to the following guidelines to help define mission scenarios and combinations of science goals.
1) Ability to address multiple science objectives with a wide range of potential instruments. Measurements/Instruments are linked either through a broad theme or through synergy available among observations.
2) Strawman payload should not be over-specified, but provides feasibility and allows creative solutions to achieve the desired science objectives to arise from the community.
3) Provides the opportunity to do science that is too big for Discovery or Scouts.
4) Either makes a new measurement, not previously done at Mars, or augments existing measurements such that the data can provide a paradigm shift or significant advance in our understanding of the planet.
5) Makes a significant step or definable progress against programmatic goals by either building on past discoveries or enabling future strategic missions.
4 Themes
The group considered a number of overarching scientific themes that might serve to steer the Mars Exploration Program in the decade following the ongoing and highly successful Follow the Water campaign. It is clear that this goal has indeed resulted in multiple locations where water has been shown to have interacted extensively with the rock record and identified high priority candidates for future landed missions. Among the broad themes discussed were those of habitability or habitable zones, dynamics or contemporary processes including atmospheric, polar and geologic processes, ancient environments, and evolution of a livable planet. In addition to these themes, a list of more specific topics was generated with regard to specific science or measurement objectives. These topics are outlined in the next section.
