What is one subtle but important analytical hurdle that Earth-based science must clear when analyzing returned samples?
Answer
Identifying signatures unambiguously Martian and preserved within the rock matrix
A risk exists of terrestrial contamination during the sealing, caching, and return journey; thus, the first task upon arrival will be distinguishing genuinely Martian signatures from anything introduced during the return process.

#Videos
What We Just Found on Mars - YouTube
Related Questions
What is the primary planet currently targeted in the focused search for extraterrestrial life?Where specifically is the Perseverance rover currently examining sedimentary rock layers?What type of chemical signatures have been discovered in sedimentary rocks by the Perseverance rover?The significance of the discovered organics is amplified because they were found embedded within minerals deposited in what specific type of environment?What scientific concept must be differentiated from biogenic origins when analyzing Martian organic molecules?Besides biological processes, what specific mechanism is mentioned as capable of producing organic compounds like methane on Mars?If Martian samples displayed a strong preference for one mirror-image version (isomer) of an organic molecule, what would this strongly suggest?Why are current on-the-spot rover analyses insufficient for definitive confirmation of ancient Martian life?What analytical approach is considered the "gold standard" for definitively confirming biosignatures from Mars?If fossilized microbial life is confirmed in returned samples, what would scientists immediately begin comparing it to?What is one subtle but important analytical hurdle that Earth-based science must clear when analyzing returned samples?