Discussion of science value of a Mars sample return

MSR pages: MSR facility - Legal Issues - science value - Dissenting views on back contamination risks

The motivation for the mission is its value for science. So evaluating its science potential is an important part of the decision process about whether to carry out the mission or not.

There is a diversity of views on its science value..

Advantages for science of a Mars sample return
The European Space Foundation report cites many advantages of a Mars sample return.

Recommendation of continued in situ study first - white paper for decadal review
This is a white paper submitted for the decadal review by eight authors from the NASA Jet Propulsion Laboratory, the Scripps Institution of Oceanography, SETI Institute, NASA Ames Research Center and the University of California Berkeley.

These authors argue that we do not yet know enough to intelligently select samples for return. They recommend a "Follow the Nitrogen strategy for in situ exploration".

They recommend that a MSR should be delayed until unambiguous biomarkers are identified in prospective Mars samples. They argue that there is a risk that samples returned at our current level of understanding may in the worst case be "as ambiguous with respect to the search for life as ALH84001."

For return of biologically interesting samples, they require ability to identify, in situ:


 * Biomarkers and unequivocal biosignatures stable over geological timescales. Examples: ability to detect chirality, and primary amine distribution.
 * Samples suitable for preserving life, and of preserving organics without significant degradation over geological time periods. Examples: sulfates, haliites, clays and the polar layered deposits
 * Nitrogenous organic compounds
 * Minute trace amounts of organics

They also recommend:
 * Any extraction methods used must preserve the target organic molecules with low degradation
 * Drilling must be carried out to the greatest depth possible, to allow for greatest chance of success for detecting organics and biosignatures.

Paige 's view
Paige raises similar concerns. He refers to a 1996 study requested by Michael Meyer of NASA’s Exobiological Program Office. This divided Mars exploration into five phases including:


 * Phase 1. Global Reconnaissance, focusing on past and present role of water, and identification of sites for detailed study.
 * Phase 2. In-Situ Exploration of Promising Sites, focusing on geologic, mineralogic, elemental, and isotopic characteristics, abundance and distribution of volatile species and organic molecules.
 * Phase 3. Deployment of exobiologically-focused experiments, and search for biomarkers of formerly living organisms, and extant life.
 * Phase 4. Robotic Return of Martian Samples to Earth, to improve characterization of organic compounds, and verify any evidence for biomarkers and extant life discovered in Phase 3.
 * Phase 5. Human exploration for detailed scientific characterizations of sites of unusual biologic interest, or inaccessible to robotic exploration.

Paige reasons that Mars exploration is still in phases 1 and 2, and that we need to complete phase 3 before going on to phase 4.

Suggested near future methods for selection of samples of biological interest
Some of the decadal review white paper, and Paige's concerns (but not all) have been addressed by the Final report of the MSR End-to End International Science Analysis Group in 2011. They stress the importance of observations to understand the geological context, They also plan to include the ESA Pasteur payload (developed for ExoMars) which includes some life detection instruments. It will for instance able for instance to detect many specific molecules likely to be associated with past or present life, with its Life Marker Chip.

The focus of this report was on missions they considered practical, so, unlike Jeffrey Bada's suggestion, they don't require deep drilling, and don't require the MSR to be delayed until unambiguous biosignatures are found.

Contamination of a returned sample by terrestrial DNA (Craig Venter)
Craig Venter (famous for sequencing the human genome) is in process of developing a miniaturized gene sequencer small enough to fit on a rover to Mars. Craig Venter's view is that this is best done in situ on Mars.

His motivation for this is that current gene sequencers are now so sensitive, that if a single micro-organism from Earth landed on the sample returned from Mars, it would ruin any experiments to test for presence of martian DNA on the sample.

Space Studies Board recommendations to avoid biological contamination of the returned sample
The Space Studies Board raise similar concern but believe biological contamination of the returned sample can be avoided by suitable decontamination procedures. This is from the 2011 review of the Space Studies Board,

Alternatives to a Mars sample return to Earth
There are proposals to study the sample extensively on the surface of Mars. There are also proposals to return the sample to quarantine facilities in Mars orbit or to Earth orbit, either before or after study on the surface.

With most of these approaches, Mars sample return would be expected eventually. The timing depends on the approach. For instance with the Bada and Paige suggestions, sample return would occur once samples are found with clear evidence of present or past life, or evidence of biosignatures in the present or past. With the telerobotics approach, sample return is done to Earth after preliminary study in orbit around Mars.

Other approaches are suggested by Zubrin and Levin (of the ICAMSR) but will be left for the separate article devoted to their views.

Extensive study of the samples first on the Mars surface


We have seen that several authors recommended in situ survey first and and Paige predicted that new instruments under development will make it possible to analyse rocks in situ on Mars, permitting a flexible approach where rovers can make new choices of targets of potential biological interest on the surface of Mars based on findings for the samples encountered earlier in the mission.

This is list of a few of the instruments under development for future Mars missions that permit or will permit preliminary study of samples with greater sensitivity than any instruments currently in use on the rovers.


 * NASA Marshall Space Flight Center is leading a research effort to develop a Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM) for future lunar and martian missions.


 * Jonathan Rothberg, and J. Craig Venter, are separately developing solutions for sequencing alien DNA directly on the Martian surface itself.


 * Levin is working on updated versions of the Labeled release instrument flown on Viking. For instance versions that rely on detecting chirality. This is of special interest because it can enable detection of life even if it is not based on standard life chemistry.


 * The Urey Mars Organic and Oxidant Detector instrument for detection of biosignatures has been descoped, but was due to be flown on ExoMars in 2018. It is designed with much higher levels of sensitivity for biosignatures than any previous instruments


 * Astrobionibbler

Vigorous study of the Mars surface instead of a sample return
Dirk Schulze-Makuch has taken this view, that a vigorous continuing study of the Mars surface would be more beneficial than a MSR at the current stage of exploration of Mars, though for rather different reasons.

Dirk Schulze-Makuch's view that from an atrobiological standpoint, in-situ research is better and cheaper than MSR
This view was given in an interview for space.com of astrobiologist Dirk Schulze-Makuch

He (along with other researchers) has published his own proposal for a mission called BOLD to send many penetrator probes to Mars to sample it sub surface and seek signs of life

Study via telepresence from Mars orbit, followed by return of the sample to Mars orbit


During the “Exploration	Telerobotics	Symposium" in 2012 experts on telerobotics from industry, NASA and academics met to discuss telerobotics, and its applications to space exploration. Amongst other issues, particular attention was given to Mars missions and a Mars sample return.

They came to the conclusion that telerobotic approaches could permit direct study of the samples on the Mars surface via telepresence from Mars orbit, permitting rapid exploration and use of human cognition to take advantage of chance discoveries and feedback from the results obtained so far.

They found that telepresence exploration of Mars has many advantages. The astronauts have near real-time control of the robots, and can respond immediately to discoveries. It also prevents contamination both ways and has mobility benefits as well.

Return of the sample to orbit has the advantage that it permits analysis of the sample without delay, to detect volatiles that may be lost during a voyage home. This was the conclusion of a meeting of researchers at the NASA	Goddard	Space	Flight	Center in 2012.

For more about exploration of Mars via telepresence, see Exploration of the surface from orbit, via telerobotics and telepresence

Decadal review conclusions in favour of near term Mars sample return
Some researchers and mission planners have put forward strong advocacy for an early Mars sample return. In particular this was one of the main conclusions of the 2011 decadal survey, an extensive survey of the community of active planetary scientists carried out every ten years in the USA.

The 2011 survey strongly advocated a Mars Sample Return program as the top flagship mission, to be carried out in several stages (with the mission to Europa proposal second).

In this survey, it was descoped due to cost considerations but the science value was considered high.

In favour of the value of sample return they cite results from previous sample returns and their analogues (e.g., of meteorites, the Moon, cometary dust, and the solar wind) and point out that the Martian meteorites known are from a limited range of rock types, so that carefully selected samples returned from Mars can greatly increase our understanding of the planet. To assist editors with verification

Some quotes from the survey report follow to show how highly the mission was valued in the survey:

These views were later summarizes as:

In the summary of the final report of the Mars Program Planning Group in September 2012, two main possibilities were considered:


 * Search for signs of past life with samples collected from a site identified using exising data and returned to Earth for analysis (pathways A1 and A2)


 * Sample Return commences only after in situ measurements and sampling of multiple sites and Science Community decision process as to which to return to Earth (pathway A3)

They comment that the first option (their pathways A1 or A2) is most directly responsive to the NRC Decadal Survey recommendations.