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I recently read of a company in Canada using robotic technology to study freshwater microbialites. Their claim is that greater understanding of terrestrial microbialites could help in the search for extraterrestrial microbialite fossils (if they exist) on Mars.

If a rover encountered a microbialite fossil on Mars, how would it identify the rock as being a fossil?

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I'm basing this answer off an article: Kevin Lepot, Karim Benzerara, Gordon E. Brown Jr., Pascal Philippot (2008). 'Microbially influenced formation of 2.7 billion-year-old stromatolites'. Nature Geoscience Vol.1 No.2, pp.118–121. DOI: http://dx.doi.org/10.1038/ngeo107

Instruments that are desirable (and are actually used) to study stromatolites/freshwater microbialites:

  • Raman microspectroscope
  • Confocal laser scanning microscope
  • Scanning transmission X-ray microscope
  • Transmission electron microscope (TEM), including high-resolution TEM
  • Near-edge X-ray absorption fine structure spectroscope
  • The usual sets of fine analytical chemistry and microcutting tools

As you might suspect, this may require rather massive, power-hungry and bulky rovers. There is a solution and it's called sample return. Although the tools and instruments are constantly evolving and undergoing miniaturization, a skilled and attentive lab researcher will find out more back here on Earth than a rover on Mars.

Another consideration in favor of sample return is the verifiability of possibly sensational results - the sample will be curated and subdivided between universities and labs worldwide, applying diverse techniques and not relying on a single set of ultra-costly but possibly systematically biased hardware.

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  • $\begingroup$ Thanks for including the reference, unfortunately that uri is unavailable (both here and on Wikipedia.) $\endgroup$ – Mark Rovetta Jul 14 '14 at 19:30
  • $\begingroup$ I understand how SEM and TEM could provide morphological evidence for a biological origin, but what features would we look for? I don't see how Raman or X-ray spectroscopy would be applicable - are you suggesting it might show evidence of organic material? $\endgroup$ – Mark Rovetta Jul 14 '14 at 19:36
  • $\begingroup$ I take your answer as: "sample return." Which is reasonable, if also a bit disappointing. I'm marking this as answered. $\endgroup$ – Mark Rovetta Jul 14 '14 at 19:41
  • $\begingroup$ @MarkRovetta - the article looks for nanoscale structures, hence the choice of instruments. It is possible to pack a robotic lab on a Mars lander (6-7 metric tonnes). $\endgroup$ – Deer Hunter Jul 15 '14 at 2:39

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