New data from NASA's Curiosity rover provides critical insights into the climate history of Mars. Currently exploring the Gale Crater, a 154-kilometer impact site, the rover has revealed details about how Mars' potentially habitable climate transformed into an inhospitable surface.
According to NASA, the findings suggest that although Mars' surface is currently hostile to life as we know it, researchers are diligently searching for signs of past life. A researcher speculates that NASA may have inadvertently destroyed evidence of life found during missions in the 1970s.
On October 7, a study was published in the Proceedings of the National Academy of Sciences, based on isotopic measurements of carbon-rich minerals from the crater. These measurements offer insights into the climatic changes that Mars has undergone.
David Burtt from NASA's Goddard Space Flight Center, the study's lead author, stated, "The isotopic values of these carbonates indicate extreme evaporation, suggesting that these carbonates likely formed in a climate that could temporarily support liquid water," which is crucial for potential life.
Isotopes are variations of elements with different masses. As water evaporates, lighter isotopes of carbon and oxygen escape into the atmosphere, while heavier isotopes remain, accumulating in carbonate rocks. These isotopes serve as a climate record, preserving characteristics of their environment, including temperature, acidity, and the composition of water and atmosphere.
The rover's data suggests two mechanisms for the formation of carbonates in Gale Crater. The first scenario involves the formation of carbonates through cycles of wet and dry conditions. The second scenario suggests formation in highly saline water under cold, ice-forming conditions.
Jennifer Stern from NASA Goddard, a co-author of the study, explained, "These formation mechanisms represent two different climatic regimes that could indicate varying habitability scenarios." The first scenario would show a transition between habitable and less habitable environments.
If the carbonates formed under the second scenario, it would indicate a less habitable environment in Mars' mid-latitudes, suggesting that most water was trapped in ice, making it unavailable for chemistry or biology, and that any available water was extremely saline and inhospitable for life.
The heavy isotope values on Mars are significantly higher than those on Earth, representing the highest recorded carbon and oxygen isotope values for the planet. Burtt noted, "The fact that these carbon and oxygen isotope values are higher than anything else measured on Earth or Mars points to a process that was pushed to the extreme," such as extreme evaporation on the Martian surface. Researchers have also found evidence of a vanished Martian atmosphere, which would have been essential for life on the planet.