Text on graphical abstract:

Mars may resemble Earth's coldest driest deserts: small niches for life adapted to extreme conditions, perhaps habitable at microbial scales only.

Earth is protected from a Mars sample return by numerous laws to protect Earth's biosphere that didn't exist in 1969.

Solution 2: study in a safe orbit above GEO first.

Above GEO. No risk to Earth's biosphere.
Tele-operated "in situ" studies of sample in satellite.
Sterilized subsamples can be returned immediately.

Legal process starts 2022. Technology decided ≥ 2028, return ≥ 2039
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NASA haven't allowed enough time to complete the legal process and build the facility to return unsterilized samples to Earth before 2039.

So we can
1. sterilize all samples or
2. check for life first - to do this, return samples to a safe orbit above GEO to study remotely with miniature instruments like those designed by astrobiologists to search for life on Mars.

With 2. we can return sterilized sub-samples from the orbital facility immediately.

In 2, a return to the ISS doesn't break the chain of containment with Mars and COSPAR decided the Moon must be kept free of contamination for future astronauts and tourists. Above GEO solves both these issues.

1. and 2. both have simple legal processes.
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Legal process starts in 2022 with the Environmental Impact Statement. Legal process ≥ 6 years. Final decision on technology ≥ 2028

By NASA regulations, build can't start until technology is decided. Build estimate: 9+ years + 2 years to train technicians.

Earliest date ready: 2028 + 11 = 2039.

Technology doesn't exist yet for ESF requirement of 100% containment of 0.05 micron particles.