An Accounting of Contamination Control Requirements, Implementation, and Verification of the Sample Tubes for the Mars 2020 Mission and Future Return Sample Science.

The Sample Tubes on the Mars 2020 Perseverance rover were required to meet strict cleanliness standards for possible organic and inorganic contamination introduction to collected samples. There were also strict planetary protection cleanliness standards required to limit possible biological contamination. Together, these sets of standards also applied to associated hardware, like the Sample Tube hermetic seals. This created unique challenges to manufacturing, cleaning, and verifying the final cleanliness state of the Sample Tubes, which are the main focus of this publication. Documenting the final cleanliness state of the Sample Tubes is critical for future analysis of collected martian samples, of significant interest to the scientific community, and will have implications for possible future missions like Mars Sample Return. An accounting of events that led to the final delivered state of the Sample Tubes on Earth with regard to contamination control cleanliness requirements, precision cleaning, processing, and verification are provided.

Universal Strength Scaling in Carbon Nanotube Bundles with Frictional Load Transfer.

Carbon nanotubes (CNTs) individually display exceptional mechanical properties, but the strength of their mesoscale assemblies such as bundles has a fundamental disconnect, with limited understanding of its scaling. Here we use coarse-grained implementation of a CNT interface with prescribed length distributions and parametrized cross-link density, providing two essential control parameters. It is shown that a linear relationship between strength of the bundles and these control parameters exists, across multiple hierarchies of nanotube interfaces. Furthermore, all geometrical perturbations caused by length distribution and bundle dimensions result in a net stress concentration effect, without influencing the scaling behavior.