If Mars has no life, must we keep Earth germs off it, and who benefits?

"To help with this effort, NASA requested that the NRC examine existing planetary protection measures for Mars and recommend changes and further research to improve such measures."

"This report discusses policies, requirements, and techniques to protect Mars from organisms originating on Earth that could interfere with scientific investigations."

"Coupled with advances in biology and life-detection techniques, these developments place increasing importance on the need to protect Mars from contamination by Earth-borne organisms."

"Protecting other bodies from terrestrial contamination (also known as forward contamination) has been a high priority for space agencies when sending spacecraft into the solar system. Even with planetary protection protocols in place to limit the prelaunch bioburden, spacecraft are being launched with terrestrial microorganisms on the surface"

"for example, the Perseverance Rover had a pre-launch bioburden of 3.86 x 10 4 spores (1)."

"After the first 24 hours on Mars, sun-facing surfaces of each spacecraft had a bioburden reduction of approx. –20 logs, indicating UVC rapidly sterilized external surfaces of each spacecraft."

"Microbes within the spacecraft themselves, or microbes that dislodged upon landing and became covered under UVC-attenuating regolith, are likely to not yet be affected by the biocidal factors of the Martian surface."

"If the internal temperature of a spacecraft was kept at 313 K, a –12 log reduction (referred to as the Sterility Assurance Level) was reached within a few sols. Colder components, such as those kept around 233 K, had a –2 log bioburden reduction after one Mars Year (668 sols), meaning colder components are sterilized much more slowly than warmer components."

"Minimizing the forward contamination of Mars from terrestrial microorganisms is a key objective of planetary protection."

"During cruise phases, the exteriors of spacecraft aeroshells were sterilized owing to solar UVC irradiation, accumulating several Sterility Assurance Levels (SALs; defined as –12 log reductions from initial starting populations of 10 6 spores per replicate) even before arriving at Mars."

"Over one Mars year, all external surfaces on all landers were likely sterilized by UVC."

"Internally, heated components of the spacecraft may reach one SAL in ∼100 sols, but nonheated internal components might take as long as 25 Mars years to be sterilized."

"Its tasks encompass sample sterilization, unsealing, processing and biological risk assessment."

"The facility is designed to support the implementation of major deep-space missions and to enable scientific research on Martian samples. Li Hang, director of the development planning department at DSEL, said the laboratory will serve scientific research findings from extraterrestrial samples."

"ensure that scientific investigations of possible extra-terrestrial life forms, precursors, and remnants are not jeopardized"

"Since the 1980s, national and international planetary protection policies have sought to avoid contamination by terrestrial organisms that could compromise future investigations regarding the origin or presence of Martian life."

"Earth is protected from the potential hazard posed by extra-terrestrial matter carried by a spacecraft returning from an interplanetary mission"

"NASA maintains a planetary protection policy to avoid the forward biological contamination of other worlds by terrestrial organisms, and back biological contamination of Earth from the return of extraterrestrial materials by spaceflight missions."

"Understanding and mitigating the potential impact of terrestrial noble gas contamination is critical to ensuring the scientific integrity of these samples."

"to preserve the integrity of Earth’s biosphere."

"Although harmful contamination is most likely to occur due to proliferation, dormant cells are also important as they can be transported to a potential habitable environment e.g., Special Regions"

"The potential for large-scale effects on Earth's environment by any returned entity released to the environment;"

"will contribute less than 0.01% and 0.1%, respectively, to the martian noble gas inventory within a sealed sample tube"

"As missions to Mars increase and diversify, national and international processes for developing planetary protection measures recognize the need to consider the interests of scientific discovery, commercial activity, and human exploration."

"We contend that at present there is neither sufficient new evidence in the literature nor scientific community consensus to conclude that the bioburden recommendation for Mars needs to be changed at this point."

"Forward-contamination issues related to Mars missions were addressed in a 2006 National Research Council (NRC) book, Preventing the Forward Contamination of Mars. However, it has been more than 10 years since back-contamination issues were last examined."

"Our results show that desorption rates decrease exponentially with time over ∼19 months"

"At the request of NASA, this report identifies criteria for determining locations on Mars potentially suitable for landed robotic missions that satisfy less stringent bioburden requirements, which are intended to manage the risk of forward contamination."

"Robotic Mars sample return missions will involve technical and design challenges in all phases of the mission in order to comply with planetary protection (PP) policies aimed at avoiding both forward and back contamination."

"This study suggests that the Mars 2020 sample tubes are suitable for capturing and preserving atmospheric samples from Mars for future scientific investigation."

"Planetary protection concerns also translate into unusual technical challenges in the design of a Sample Receiving Facility (SRF) where martian materials will be handled during screening and testing based on a Draft Protocol."