In Situ Analysis

Pros. The advantages of in situ analyses on Mars include the following:

  • Feasibility of analysis on shorter timescale because of funding levels; more missions can be flown to multiple sites;

  • Possibility of time-resolved measurements of variable processes;

  • Possibility for analysis of more samples, which would provide additional context and flexibility;

  • Ability to look at labile components, with no storage issues;

  • Opportunity for active experimentation (manipulation of materials and observation of response);

  • No planetary-protection issues associated with Earth return; and

  • In situ instrument development that feeds forward for other future missions.

Cons. The disadvantages of in situ studies of martian samples include the following:

  • Requirement for additional instrument and spacecraft technology development;

  • Possibility that sample handling may be too complex for the types of analyses desired;

  • Inability to adjust analytical capabilities in response to discoveries;

  • Long lead times for instrument development;

  • Inability of mission to carry more than a limited number of instruments; and

  • Likelihood that some desirable analyses will never be possible in situ on Mars.

Value of Complementary Approach

In situ measurements conducted in the context of a sample-return mission have the following desirable characteristics:

  • Selection of the most valuable return samples;

  • Understanding of the detailed geological context in which the samples are found; and

  • Potential to maximize the scientific return from the chosen samples.

precursor to any human exploration of Mars.2224 As such, it must be integrated into the long-term strategic planning for Mars exploration.

Various methods have been proposed to acquire martian samples. These include grab sampling (using a scoop or arm on a lander or collection of airborne dust during a flyby through the upper atmosphere), sampling a variety of rocks and soils by using a rover, obtaining subsurface samples using a drill, conducting a Phobos sample return that might contain Mars ejecta from large impacts, or collection by astronauts.

To maximize the astrobiological potential of a sample return from Mars, it will be important to recover a wide range of materials from a well-characterized site of astrobiological interest. This requirement immediately raises a longstanding strategic question: Is it appropriate to wait until sufficient knowledge has accumulated to identify the “right sample” or to get a sample from the best place identifiable today? Proponents of the “right sample” approach typically argue that spending billions of dollars to return the “wrong sample” would be a major setback to the Mars Exploration Program. The biggest concern about getting the “right sample” is that, once this approach

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