Description
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The Time-Temperature Tiger Team (T4) was chartered by NASA and ESA to evaluate the risks to the scientific return of Mars Sample Return (MSR) samples if they are exposed to temperatures between +30 and +60 ⁰C. Thirteen scientists, were selected to represent the scientific disciplines that are expected to be the ones most affected if such heating were to happen. The expertise of the team helped in understanding whether exposing the MSR samples to temperatures between +30 and +60 ⁰C will pose any risk to the sample integrity and therefore, to future scientific investigations. Key processes identified by the T4 were: the release of volatiles by desorption and sublimation and release from condensed phases (interiors, decomposition, dehydration); chemical reactions including gas-gas and gas-solid; deliquescence of hygroscopic salts; acid/base interactions (potential for extreme pH conditions); aqueous redox reactions, isotopic exchange (aqueous phases, minerals, gasses, organic phases); condensation and freezing (in the after-heating cooling phase) and interactions with the sample tube materials. There is potential for multiple interactions and overlapping effects. For inorganic materials and the records they represent, over both long time scales (hours to days) and short time scales (minutes to hours) no temperature excursion above +30 °C could be accommodated without loss of science. There will be some robust constituents (feldspars, quartz, pyroxenes, etc.) that are unaffected, but also some less robust constituents (salts, phyllosilicates, radicals, etc.) that are affected across all temperature ranges ≤60 °C. For organic materials, and in particular organic biosignatures, the risks reflect that preservation is reliant on a number of processes and a change in one component within a sample tube can affect another. For organic materials, over long time scales (hours to days), no temperature excursion above +30 °C could be accommodated without loss of science, but over short time scales (minutes to hours) raising the temperature to 40 °C could be manageable without major disruption to science while temperatures above 40 °C would lead to significant losses. The findings will help to maintain the fidelity of samples returning from Mars in the future and maximize scientific return when analyzed in Earth laboratories.
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