Life on Mars?
Do you believe therewas past life on Mars? Here’s what new NASA evidence indicates.
Dry, cold and barren.Mars doesn’t seem like a haven for life—at least not the kind humans arefamiliar with.
Scientists havewondered for decades if microbial life could have inhabited Mars in the distantpast. One study, based on data collected by NASA’s Curiosity rover, is peelingback a layer of the mystery. Researchers measured the isotopic composition ofcarbon-rich minerals found in Gale Crater. This region is laced with driedrivers and gullies and was explored by the rover.
The findings Curiositysent to Earth were not optimistic about the potential for life above ground.But that doesn’t rule out the possibility of an underground biosphere or even asurface biosphere that began and ended before the carbonates were formed.
This suggests twopossible ways carbon-rich minerals could have form at Gale crater: a series ofalternating wet and dry periods or salty-ice conditions. These two climatescenarios could be called ‘bleak’ and ‘bleaker’ when it comes to supportinglife.
In an environment thatswings from wet to dry, the region would shift from more habitable to lesshabitable. In the frigid temperatures near Mars’ equator, that environmentwould be hostile for life because most water would be frozen and inaccessiblefor chemistry or biology. Plus, what water was there was extremely salty, notpleasant for life.
This isn’t the firsttime scientists have theorized these climate scenarios for ancient Mars.Previous computer models have indicated these conditions before, but now theyhave isotopic evidence from Martian rocks.
Scientists have soughtlife on Mars since the first spacecraft touched down there in 1976. Mountingevidence from robotic explorers has shown the Red Planet to have been warmerand wetter, perhaps more than 3 billion years ago.
The Perseverance rover discovereda spotted rock with compelling signs of ancient dead Martian life, but a samplewould need to be shipped to Earth for confirmation. A research team alsoreported evidence of a vast ocean of water below the planet’s surface. OnEarth, where there’s water, there’s often life.
Scientists areinterested in Mars’ carbon-rich rocks because they can hold clues about theenvironment in which they formed, such as the temperature and acidity of thewater, and ingredients in the water and air.
The sampled rocksindicate lots of evaporation, suggesting a climate that could only supporttransient liquid water—that is, ice that melts when temperatures rise and thesurface pressure is right.
The heavy isotopevalues in the rocks are much higher than what’s seen on Earth. They are theheaviest carbon and oxygen isotope values recorded for any Martian materials.Although evaporation can cause oxygen isotope changes on Earth, the changes inthe Martian samples were two to three times greater.
But this doesn’t negatethe possibility of life. Mars has a network of deep caves formed by ancientvolcanic vents. Within the caves could be liquid water, traces of long-deceasedbacteria or fungi, or perhaps even existing microbial life.
Caves can host complexecosystems, including extremophiles that munch on rocks and convert thematerial into energy for life. So, many astrobiologists want to go spelunkingon Mars. Would you like to join them?
