In the “Valley of Life” Gale Crater, the Curiosity rover has discovered new evidence regarding the climatic evolution of the red planet.
Curiosity is one of the warriors in the search for life that NASA has sent to Mars, and the Gale Crater area it is exploring used to be an ancient river plain.
Although it found “building blocks of life” here several years ago, Curiosity is still on a quest for something more specific, including evidence of ancient organisms and geological signs of a Mars that may have once had a climate similar to that of ancient Earth.
Curiosity Rover on Mars – (Graphic: NASA/JPL-Caltech).
Recently, several samples of carbonate-rich minerals collected by Curiosity and preliminarily analyzed by its onboard “laboratory” have been further examined by scientists using indirect tools from Earth.
“The isotopic values of these carbonate minerals indicate extreme evaporation, suggesting that they could only have formed in a climate that could temporarily support liquid water” – Dr. David Burtt from NASA’s Goddard Space Flight Center stated.
This new discovery is not good news for life. “Our samples do not match the biosphere on the surface of Mars, although this does not rule out the possibility of a subsurface biosphere or a surface biosphere that began and ended before these minerals formed” – Dr. Burtt explained.
As water evaporates, lighter isotopes of carbon and oxygen are more likely to escape into the atmosphere, while the heavier isotopes remain, accumulating in greater masses.
Thus, carbonate rocks have inadvertently recorded the climatic history of the area in which they exist.
The isotopes that NASA recently recorded indicate that at least in Gale Crater, there are two plausible scenarios related to the formation mechanisms of carbonates.
- In the first scenario, carbonates formed through a series of wet-dry cycles.
- In the second scenario, carbonates formed in very salty water under cold conditions, leading to ice formation.
These mechanisms represent two different climate regimes and also two different scenarios for a biosphere that is believed to have once existed on the planet.
The wet-dry cycle would indicate a shift between more habitable environments and harsher living conditions, suggesting that any organisms here may have experienced tumultuous environmental phases similar to those on Earth.
In the colder second scenario, ancient Martian life would have had to “struggle” much more than Earth life if they ever did exist.
Regardless of which scenario is correct, the journey of Curiosity and other life-searching robots is still far from over.
