Helium Leak Rate Measurements of Flight-like Mars 2020 Sample Tubes

The sample tubes on board NASA's Perseverance rover are designed to contain rocks, regolith, and atmospheric gases and are hermetically sealed on the surface of Mars to minimize sample loss, alteration, and contamination. Following a robust testing program during mission development, it was determined that the helium (He) leak rates of flight-like sample tubes sealed under a range of conditions were typically no greater than ∼10^-10 standard cubic centimeters per second (scc/s); leak rates below this value could not be measured since this is the detection limit of commercially available He leak detectors. This limit was adequate to meet mission requirements. However, some scientific objectives could be compromised by sample tube leak rates even below 10^-10 scc/s, thus motivating a more sensitive technique for establishing leak rates. This study investigated He leak rates on six flight-like sample tubes using a static mode mass spectrometer. Room temperature He leak rates of the six sample tubes ranged from ∼8.8 × 10^-17 to ∼4.6 × 10^-14 scc/s. One sample tube was analyzed at eight different temperatures, ranging from -51°C to +42°C, and yielded He leak rates correlated with temperature that varied from ∼1.7 × 10^-15 to ∼1.4 × 10^-13 scc/s, respectively. Our results confirm and extend previous findings demonstrating that the Mars 2020 sample tube seals are likely to be very leak-tight, with leak rates <10^-13 scc/s. These leak rates are sufficiently low that the impact of gas egress or ingress is expected to be negligible.