Supercritical CO2 Cleaning for planetary protection and contamination control

We have designed and built a new Supercritical CO2 Cleaning (SCC) system1,2 to conduct cleaning efficiency studies using Supercritical CO2 and liquid CO2 to remove trace amounts of microbial and organic contaminants from spacecraft material surfaces. The objective of this task is to develop an effective CO2 cleaning method and to demonstrate and validate its ability to achieve ultra-clean surfaces of sample handling devices, sample storage units, and science instruments. This new capability will meet planetary protection and contamination control requirements for future Astrobiology science missions. The initial cleaning test results using this new cleaning device showed that both supercritical CO2 and liquid CO2 could achieve cleanliness levels of 0.01 µg/cm2 or less for hydrophobic contaminants. Experiments under supercritical condition using compressed Martian air mix, which consists of 95% CO2, produced similar cleaning effectiveness on the hydrophobic compounds. This opens up the possibility of further development potential for in situ CO2 cleaning and sterilization using Martian air for future Mars missions. We plan to further investigate the cleaning condition for hydrophilic compounds and bacterial spores, as well as introducing polar co-solvent to the cleaning apparatus.