Desorption of Terrestrial Noble Gases in Mars 2020 Sample Tubes: Implications for Mars Sample Return.

The Mars Sample Return (MSR) Campaign aims to collect and transport to Earth samples of martian atmosphere contained in sample tubes onboard the Mars 2020 rover, Perseverance. Understanding and mitigating the potential impact of terrestrial noble gas contamination is critical to ensuring the scientific integrity of these samples. This study quantifies the desorption of terrestrial argon (⁴⁰Ar) and xenon (¹²⁹Xe) from the interior of a flight-like Mars 2020 sample tube under high vacuum and provides critical insights into the potential contamination risks for returned martian atmospheric samples. Our results show that desorption rates decrease exponentially with time over ∼19 months and that desorbed terrestrial ⁴⁰Ar and ¹²⁹Xe will contribute less than 0.01% and 0.1%, respectively, to the martian noble gas inventory within a sealed sample tube that consists of martian atmosphere at a pressure of ∼7 mbar. This study suggests that the Mars 2020 sample tubes are suitable for capturing and preserving atmospheric samples from Mars for future scientific investigation.