I may be in the minority opinion but I consider planetary protection absurd. If there is life, it will be eventually found. Until large scale terraforming efforts start any bacterial life will be uniformly spread across the planet unless it was recently added. Life spreads across a body on the order of decades, not billions of years. All life on Earth shares a huge amount of its DNA. If it's based on life from Earth it will be immediately obvious. If it's actual life from Earth brought with people/rovers then we'll also immediately know.NASA should immediately remove the office of planetary protection. It's a nuisance and serves no purpose except for perpetuation of non-science appeals to nature.
A new report recommends that NASA update its policies that protect planets and other solar system bodies from possible contamination during space exploration missions.The current process for planetary protection policy development is inadequate, according to the report, which was published by the U.S. National Academies of Sciences, Engineering and Medicine. It notes that private-sector space exploration activities are another reason why planetary protection policies need re-examination.The 170-page report — "Review and Assessment of Planetary Protection Policy Development Processes" — calls for NASA to develop a strategic plan for planetary protection, assess the completeness of policies and initiate a process to formally define requirements that are missing.
Spotlighted in the report are Mars sample-return missions and exploration campaigns to the icy, ocean-harboring moons of Jupiter and Saturn.
"It's extremely unlikely that terrestrial bacteria will eat up any hypothetical martian microbes. The environment will be too hostile for terrestrial organisms to thrive, indigenous forms will out compete them. We see that on Earth. Nor is it likely that that they will eat them, biochemistry will be too alien."I agree with most of your arguments. However, there is at least one example of fast evolutionary adaptation of an organism to new potential "sources of food" on our planet: "In 2016, scientists from Japan tested different bacteria from a bottle recycling plant and found that Ideonella sakaiensis 201-F6 could digest the plastic used to make single-use drinks bottles, polyethylene terephthalate (PET). It works by secreting an enzyme (a type of protein that can speed up chemical reactions) known as PETase. This splits certain chemical bonds (esters) in PET, leaving smaller molecules that the bacteria can absorb, using the carbon in them as a food source.Although other bacterial enzymes were already known to slowly digest PET, the new enzyme had apparently evolved specifically for this job." (https://www.independent.co.uk/news/science/plastic-eating-bacteria-chemist-science-pollution-pet-recycling-a8311811.html).Therefore, we should not underestimate the ability of terrestrial life forms to adapt and evolve. In order to sustain any permanent human presence on Mars, we need to import lots of earthly life forms (plants, soil microflora and microfauna, small and medium animals). Scientist may want to conduct terraforming experiments involving genetically modified organisms artificially adapted to Mars conditions. But this is exceeding the topic of this thread.