Review of Goals and Plans for NASA's Space and Earth Sciences (2006)

Given the schedule constraints for generating the roadmaps, the Robotic and Human Exploration of Mars roadmap provides a generally reasonable approach to future Mars science exploration during the next three decades.¹ The roadmap’s strengths are its early recognition of broad scientific goals, consideration of preparations for human exploration, and strategies for developing the next generation of Mars scientists. Its major weakness is the lack of broader scientific goals and objectives as motivation for the roadmap’s specific recommended mission elements, which focus on putting humans on Mars. The roadmap’s presentation of the goal of placing humans on Mars appears without scientific justification.

The discussion that follows addresses the major elements of the roadmap from the perspectives of scientific merit, crosscutting opportunities, realism of schedule, resources, technology, prioritization, and decision making, as well as potential relationships with other government agencies for Mars exploration.

The broad goals stated in the Robotic and Human Exploration of Mars roadmap’s executive summary (most notably in the table) and in the first few pages of the body are consistent with recent NRC documents and overarching themes of Mars science goals.^2-8 However, these early stated goals are disconnected from what is elaborated in the rest of the roadmap. In general, real discussion of prioritized goals, observations, and measurements within the broad science context has been sacrificed to address the human exploration goals. For example, the body of the roadmap repeatedly mentions water and life as science drivers, yet large-scale and important science goals such as characterization of climate (e.g., microclimates and climate history), the radiation environment, polar processes, atmosphere-surface interactions, and the martian crust and interior science are largely ignored. These science goals, equal in importance to the goal of human exploration, are well articulated in recent reports, especially in the NRC report Assessment of Mars Science and Mission Priorities.⁹ Overall, it is unclear how these science goals feed into the roadmap’s planned mission lines.

The panel recommends careful reconsideration of the broad science goals and priorities for Mars studies set forth in the NRC solar system decadal survey New Frontiers in the Solar System when the robotic and human exploration of Mars is planned using this roadmap. This approach will help reintroduce important science goals into the planning process that are currently underrepresented or missing from the roadmap.

The roadmap’s retention of existing and previously planned missions (Mars Reconnaissance Orbiter, Phoenix, Mars Science Laboratory, Mars Sample Return) is appropriate and reasonable. These missions are cited and prescribed in numerous past reports and community documents from the NRC and the Mars Exploration Program Analysis Group (MEPAG).^10-12 The inclusion of a possible Mars Environment Mission is also reasonable. However, the panel identified specific problem issues with the

roadmap’s recommended mission architecture for the coming decade, and the roadmap makes no attempt to identify missions beyond that time. The issues are as follows.

Two Mars Science Laboratory (MSL) rover missions are prescribed in the Mars roadmap. However, there is no description of the second MSL (raising questions such as, Would its payload be the same as that of the first MSL?), and there is no justification provided for its scientific need.^a Furthermore, the NRC’s solar system decadal survey recommended that technologies required for sample return be validated during an MSL mission,¹³ but that is not part of the mission presented in this roadmap. MSL missions are expected to cost in excess of $1.5 billion, so the decision for a second MSL mission has significant budgetary impacts on the long-range achievability of the overall Mars exploration plan and how long-range science goals are traded off against a second large mission.¹⁴ In addition, it is unclear how the options in the Mars roadmap will be selected, because no decision rules are provided. As presented, NASA’s selection of the roadmap’s first option would put the Mars Telecommunication Orbiter at risk, threatening future mission communications because current systems are aging.

Similarly, the roadmap presents two possible Mars Environment Mission (MEM) scenarios for 2013—an orbiter or a drilling lander. Again, the MEM descriptions focus solely on the precursor-to-human-exploration aspects of the missions and, as such, represent a diversion from previously recommended missions (Mars Long-Lived Lander Network and Mars Upper Atmosphere Orbiter) for the next decade.¹⁵ Although a decision on which MEM option to pursue is recommended for 2008, no science-based decision rules are given. Nor is there a technology development timeline that would lead to a decision point based on the technological readiness of autonomous drilling should the drilling lander option be selected.

The Mars Sample Return (MSR) mission is arguably the cornerstone of Mars exploration science as articulated in previous documents and in this roadmap.^16-19 However, sample return comes with a plethora of critical forward and back contamination issues concerning sample collection, handling, and quarantine that are not addressed in this roadmap. Significant technological hurdles associated with return and described elsewhere^20-24 are also not considered. The NRC has previously estimated that at least 7 years will be required to prepare a quarantine facility, which will strain the schedule of a launch only 9 years away.²⁵ The quarantine facility, other infrastructure, and enabling technologies (e.g., containment, sterilization, or both) need to be considered as carefully as the human exploration architecture.

Identification of the scientific need for and value of humans in future Mars exploration is conspicuously absent from the Mars roadmap. A case can be made for the science value of humans in

space exploration (e.g., their ability to perform complex experiments beyond the capabilities of robots, such as deep subsurface drilling), and program content should reflect this benefit. Moreover, the roadmap should recognize and address the non-science motivation for a human presence. Although it is clear that a major motivation for proposing human exploration of Mars involves national prestige and inspiration for the entire world, the charge for this panel compels it to address the scientific elements of such an effort.

An underlying assumption in the roadmap is that the surface of Mars either is habitable or can be made habitable for future human exploration. However, unlike the lunar surface, soils of Mars may be hazardous (highly acidic, potentially corrosive, toxic), and there is a real potential that human exploration may be prohibited, restricted, or delayed for safety reasons.^26,27 In addition, current international restrictions are in place concerning both forward and back contamination of other habitable planets and the return of materials from Mars.^28,29 A primary goal of the Mars Exploration Program is to understand the potential for life and to explore habitats for possible signatures of extinct or extant life. Discovery of past or present indicators of life would clearly have a transformative impact on many fields of science. However, placing what is essentially an Earth biosphere on Mars can compromise these goals, and there may be quarantine restrictions on materials astronauts have used that have come in contact with the martian surface. Because the roadmap emphasizes a human presence over other scientific endeavors, it opens the risk that the Mars science program could be jeopardized should the human exploration of the planet prove to be hazardous or impossible because of restrictions on cross-contamination with Earth.

The panel’s evaluation concerns are heightened in this case, because the considerable expense of human expeditions to Mars may have an adverse effect on the funding available for robotic science.

The Mars roadmap does not characterize mission lines by size (small, medium, large), making it difficult to consider the reasonableness of required resources in relation to budgetary constraints. However, estimates from other sources indicate that MSL and MSR missions will be in the large flagship class (i.e., in excess of $1 billion) and will put pressure on Mars program resources.^30,31 A second MSL rover mission could push MSR out into the 2020 decade. The smaller Scout missions represent community-driven science that is consistent with previous objectives. The NRC solar system decadal survey strongly recommended that Scout missions receive the same commitment as sample return. However, the Mars roadmap’s recommended missions put Scout missions at risk, especially if a second MSL is chosen. Furthermore, although the roadmap acknowledges that specific Scouts cannot be defined now for the future, the fact that much high-priority science will not be accommodated in the main mission lines should allow identification of several high-priority Scout mission scenarios or science areas. In general, the lower-cost, high-science-return Scout mission line is underrepresented in the roadmap. Furthermore, after Mars Telecommunication Orbiter (MTO) no plans are presented for a medium-class mission line—instead it appears that resources will be directed into a larger flagship budgetary class.

The panel believes that the lack of smaller missions puts science discovery at risk, and it recommends that clear budget lines for small- (Scout-class) and medium-scale missions be developed for the long-term robotic exploration of Mars.

Because resources are limited, NASA should identify areas in which missions can serve multiple scientific goals. There are many crosscutting opportunities between the roadmaps. Several important crosscutting opportunities for the Robotic and Human Exploration of Mars roadmap follow:

• With Sun-Solar System Connection. There is potential for a shared or partnership approach to achieve multiple scientific goals. Although the interplanetary radiation environment is fairly well

characterized, the very intense solar energetic particle events that may require action remain poorly understood and very difficult to predict. The Sun-Solar System Connection roadmap recommends a Mars radiation environment and space weather mission, as well as an Inner Heliospheric Sentinels mission to study hazardous solar energetic particle events.

• With Lunar Exploration. The panel commends the Mars roadmap’s recognition that requirements for human exploration at Mars should drive human lunar exploration. To maintain this important perspective, it is necessary that there be close collaboration and communication between the two programs to ensure unity between them.

  The panel recommends that NASA formally link all robotic and human lunar exploration to the robotic and human Mars exploration program’s needs and requirements. The scope of this linkage should include science, technology, and infrastructure.

• With Earth Science. The Mars roadmap mentions the problem of working with large data sets and an ever-increasing volume of data. Work in the Earth science community with large global data sets integrated across instruments on multiple platforms can serve as models for this task. Utilization of previous Earth science experience and collaboration on future developments in this area would benefit both programs.

The Mars roadmap identifies key workforce needs and facilities required to support the Mars Exploration Program. However, two equally important core infrastructural needs for the next decade of exploration recommended in the roadmap are autonomous drilling (a MEM option) and a sample quarantine facility and related infrastructure (for MSR). The infrastructural issues for meeting the mission timelines during the next decade are significant and are underemphasized in discussion in the roadmap. The NRC has produced recommendations for MSR infrastructure in previous studies.^32,33

Although the Mars roadmap lays out a strategy to “define, downselect, and confirm” a human exploration architecture,³⁴ it does not describe a similar process for selecting various mission option paths, the population of those missions with scientific goals and objectives, or architectures for nearer-term objectives such as preparation for and implementation of MSR. The roadmap is also not clear about how the mission sequence depends on new discoveries. For example, does MSR depend on any specific discoveries (e.g., organic carbon) in precursor missions?

As indicated above, the budget and schedule for two MSLs appear overambitious. Cost estimates suggest that a single MSL will be in the large, flagship mission class (greater than $1 billion).^35,36 A second MSL poses significant fiscal and schedule risk and will likely push the whole Mars program out by at least one mission opportunity and will put accomplishing other goals in the program at risk. In the single-MSL option, a critical technical risk is posed in that a Mars Telecommunication Orbiter may not be present for communications to MSL. In general, the phasing of resources in regard to logistic, operational, and technical needs is not sufficiently considered for the phase-1 portion of the Mars roadmap. For example, the significant technological and infrastructure needs for MSR are inadequately addressed.

There is no substantial discussion in the Mars roadmap concerning participation of other NASA and non-NASA entities in the program. The panel encourages the broad integration of required observations across traditional discipline lines within NASA and in concert with other U.S. agencies and international partners. Specifically, within NASA, a number of complementary goals are recognized that are relevant to understanding the environment on and around Mars within which human exploration will take place. Some of these are addressed in the other roadmaps and in the NRC report The Astrophysical Context of Life.³⁷ Beyond NASA, there is a potential for contributions in this area from the National Science Foundation, the National Institutes of Health, the Department of Energy, and the U.S. Department of Agriculture, as outlined in the NRC report Life in the Universe.³⁸ These other federal agencies can provide input with regard to assessment of the radiation and biological hazards posed by the martian environment and definition of life-detection methods to be utilized in situ.^39,40

1. National Aeronautics and Space Administration (NASA), Advanced Planning and Integration Office. 2005. Robotic and Human Exploration of Mars. NASA, Washington, D.C. Available at <www.hq.nasa.gov/office/apio/pdf/mars/mars_roadmap.pdf>.

2. National Research Council (NRC). 2003. New Frontiers in the Solar System: An Integrated Exploration Strategy. The National Academies Press, Washington, D.C.

3. NRC. 2003. Assessment of Mars Science and Mission Priorities. The National Academies Press, Washington, D.C.

4. NRC. 2002. The Quarantine and Certification of Martian Samples. National Academy Press, Washington, D.C.

5. NRC. 1997. Mars Sample Return: Issues and Recommendations. National Academy Press, Washington, D.C.

6. NRC. 2002. Safe on Mars: Precursor Measurements Necessary to Support Human Operations on the Martian Surface. National Academy Press, Washington, D.C.

7. Mars Exploration Program Analysis Group. 2004. Scientific Goals, Objectives, Investigations and Priorities: 2004. July 16. Available at <mepag.jpl.nasa.gov/goals/MEPAGgoals-approved071604.pdf>.

8. Beaty, D.W., K. Snook, C.C. Allen, D. Eppler, W.M. Farrell, J. Heldmann, P. Metzger, L. Peach, S.A. Wagner, and C. Zeitlin. 2005. An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Missions to Mars. June 2. Available at <mepag.jpl.nasa.gov/reports/MHP_SSG_(06-02-05).pdf>.

9. NRC. 2003. Assessment of Mars Science and Mission Priorities.

10. NRC. 2003. New Frontiers in the Solar System.

11. NRC. 2003. Assessment of Mars Science and Mission Priorities.

12. Mars Exploration Program Analysis Group (MEPAG). 2004. Scientific Goals, Objectives, Investigations and Priorities: 2004.

13. NRC. 2003. New Frontiers in the Solar System.

14. MEPAG. 2004. Scientific Goals, Objectives, Investigations and Priorities: 2004.

15. NRC. 2003. New Frontiers in the Solar System.

16. NRC. 2003. New Frontiers in the Solar System.

17. NRC. 2003. Assessment of Mars Science and Mission Priorities.

18. NRC. 1997. Mars Sample Return: Issues and Recommendations.

19. MEPAG. 2004. Scientific Goals, Objectives, Investigations and Priorities: 2004.

20. NRC. 2003. New Frontiers in the Solar System.

21. NRC. 2003. Assessment of Mars Science and Mission Priorities.

22. NRC. 2002. The Quarantine and Certification of Martian Samples.

23. NRC. 1997. Mars Sample Return: Issues and Recommendations.

24. NRC. 2002. Safe on Mars.

25. NRC. 2002. The Quarantine and Certification of Martian Samples.

26. NRC. 2002. Safe on Mars.

27. Beaty et al. 2005. An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Missions to Mars.

28. NRC. 2002. Safe on Mars.

29. MEPAG. 2004. Scientific Goals, Objectives, Investigations and Priorities: 2004.

30. NRC. 2003. New Frontiers in the Solar System.

31. Beaty et al. 2005. An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Missions to Mars.

32. NRC. 2002. The Quarantine and Certification of Martian Samples.

33. NRC. 1997. Mars Sample Return: Issues and Recommendations.

34. NASA, Advanced Planning and Integration Office. 2005. Robotic and Human Exploration of Mars.

35. NRC. 2003. New Frontiers in the Solar System.

36. Beaty et al. 2005. An Analysis of the Precursor Measurements of Mars Needed to Reduce the Risk of the First Human Missions to Mars.

37. NRC. 2005. The Astrophysical Context of Life. The National Academies Press, Washington, D.C.

38. NRC. 2003. Life in the Universe: An Assessment of U.S. and International Programs in Astrobiology. The National Academies Press, Washington, D.C.

39. NRC. 2002. Safe on Mars.

40. NRC. 2002. Signs of Life: A Report Based on the April 2000 Workshop on Life Detection Techniques. The National Academies Press, Washington, D.C.