Thats because its possible for geological featuresproduced by non-biological processes to resemble fossils.
These are referred as pseudofossils.
Thats why Perseverance isnt just looking for fossils on site: its collecting samples.
Perseverance’s view of ‘unsen Peak.Image: NASA/JPL
This rock unit may have formed alongthe shoreline of the ancient lake.
But whats so special about carbonates?
One ingredient in habitability is the availability of water.
Carbonate and silica minerals can both form by direct precipitation from liquid water.
Second, we know from examples on Earth that ancient sedimentary carbonates can yield wonderful fossils.
Such fossils include stromatolites composed of carbonate crystals precipitated directly by bacteria.
Perseverance hasnt seen convincing examples of these.
There are someconcentric circular patternsin the Margin Unit but they are almost certainly an effect of weathering.
The small grain size of the Comet Geyser sample indicates a higher potential to preserve delicate fossils.
Modified mission architectures are now being evaluated to meet these challenges.
Mars sample returnremains NASAs highest planetary science priorityand is strongly supported by the planetary science community around the world.
The samples from Perseverance may revolutionise our view of life in the universe.
Lets hope NASA and the U.S. government can live up to the name of their rover, and persevere.
Sean McMahon, Chancellors Fellow in Astrobiology,The University of Edinburgh.
This article is republished fromThe Conversationunder a Creative Commons license.
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