Mitigation of the Impact of Terrestrial Contamination on Organic Measurements from the Mars Science Laboratory

Abstract

The objective of the 2009 Mars Science Laboratory (MSL), which is planned to follow the Mars Exploration Rovers and the Phoenix lander to the surface of Mars, is to explore and assess quantitatively a site on Mars as a potential habitat for present or past life. Specific goals include an assessment of the past or present biological potential of the target environment and a characterization of its geology and geochemistry. Included in the 10 investigations of the MSL rover is the Sample Analysis at Mars (SAM) instrument suite, which is designed to obtain trace organic measurements, measure water and other volatiles, and measure several light isotopes with experiment sequences designed for both atmospheric and solid-phase samples. SAM integrates a gas chromatograph, a mass spectrometer, and a tunable laser spectrometer supported by sample manipulation tools both within and external to the suite. The sub-part-per-billion sensitivity of the suite for trace species, particularly organic molecules, along with a mobile platform that will contain many kilograms of organic materials, presents a considerable challenge due to the potential for terrestrial contamination to mask the signal of martian organics. We describe the effort presently underway to understand and mitigate, wherever possible within the resource constraints of the mission, terrestrial contamination in MSL and SAM measurements.

Solid-Phase Microextraction for Organic Contamination Control Throughout Assembly and Operational Phases of Space Missions

“…Other techniques are also employed in these cases, using plasma, accelerated CO2 snow, radiation, or electron beams to remove organic compounds (National Research Council, 2000ten Kate et al, 2008;Dworkin et al, 2018). Repeated wiping of surfaces with clean room cloths saturated with propan-2-ol or ethanol during assembly prevents the rebuild-up of certain molecular contaminants, although this does not protect against all species, for example, silicones are unlikely to be removed in this manner.…”

“…Inventories of materials used during construction of spaceflight hardware and their potential for contamination are also required to be stored for potential future testing to allow for identification of suspected contaminants in experimental results from spacecraft instruments (Mahaffy et al, 2003). Such a materials database was created for monitoring during the ongoing MSL mission (ten Kate et al, 2008). Potential materials for use in the most contamination sensitive parts of the ExoMars rover were thoroughly tested to determine their appropriateness for use and to calculate contamination budgets (Guarnieri et al, 2009).…”

Mars Science Laboratory Mission and Science Investigation

“…Steps have been taken to ensure that the SAM measurements of soil and rocks on Mars do not contain terrestrial contaminants above the SAM detection levels (ten Kate et al 2008). However, it is likely that a slight amount of terrestrial contamination may be present despite our best efforts.…”

Determining the local abundance of Martian methane and its’ 13C/12C and D/H isotopic ratios for comparison with related gas and soil analysis on the 2011 Mars Science Laboratory (MSL) mission

“…To that end, in addition to the fastidious planetary protection requirements and implementation for MSL instruments, the SAM team have developed a contamination model, a material archive, and created a library of organics used on MSL that may show up on Mars (Ten Kate et al, 2008). This has involved the analysis of numerous MSL materials, with dozens of GCMS pyrolysis runs and hundreds of compounds, an effort that will continue into the mission.…”