Planning Implications Related to Sterilization-Sensitive Science Investigations Associated with Mars Sample Return
Michael A Velbel1,2, Charles S Cockell3, Daniel P Glavin4
1Michigan State University, Earth and Environmental Sciences, East Lansing, Michigan, USA.
Astrobiology
|December 14, 2021
Summary
Sterilizing Mars samples with heat or radiation compromises most life-detection and paleoenvironmental measurements, corrupting evidence of Martian life and its history. Unsterilized sample analysis within containment is crucial for accurate scientific results from the Mars Sample Return Campaign.
Area of Science:
- Astrobiology and Planetary Science
- Geochemistry and Astromaterials Analysis
- Space Mission Science Operations
Background:
- The NASA/ESA Mars Sample Return (MSR) Campaign aims to determine if life ever existed on Mars.
- Planetary Protection requirements may necessitate sterilization of returned Martian samples before terrestrial laboratory analysis.
- The impact of sterilization on the scientific integrity of returned samples is a critical consideration for mission success.
Purpose of the Study:
- To assess the effects of proposed sterilization methods (dry heat and gamma irradiation) on the scientific value of returned Martian samples.
- To identify which types of measurements are sterilization-sensitive and which are sterilization-tolerant.
- To inform the design and capabilities of the Sample Receiving Facility (SRF) for the MSR Campaign.
Main Methods:
- Evaluation of sterilization effects on organic molecules, minerals, and volatile-rich materials.
- Consideration of two dry heat regimes (180°C for 3 hours; 250°C for 30 min) and gamma irradiation (1 MGy).
- Analysis of impacts on measurements of biosignatures, paleoenvironmental indicators, and elemental/isotopic compositions.
Main Results:
- Over half of life-detection measurements (86% for extant life) are sterilization-sensitive and cannot be reliably performed on sterilized samples.
- Approximately 72% of geological and atmospheric measurements are sterilization-tolerant.
- Both heat and gamma irradiation significantly compromise measurements of organic molecules, redox-sensitive elements, and isotopes, corrupting evidence of past life and environmental conditions.
Conclusions:
- Sterilization methods critically compromise key scientific objectives of the Mars Sample Return Campaign, particularly those related to life detection and paleoenvironmental reconstruction.
- Measurements of sterilization-sensitive properties must be performed on unsterilized samples within biocontainment, necessitating additional analytical capabilities in the SRF.
- Sterilization-tolerant measurements can be performed on sterilized samples outside containment, optimizing resource allocation and safety protocols.
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