Curiosity, launched by the space agency to go to Mars in 2011, is conducting research in Gale crater on the Red Planet. These studies aim to reveal the habitability potential of Mars.
To that end, Curiosity studies sedimentary rocks filled with clay minerals in Gale crater. Because clay could mean that liquid water, an essential ingredient for life, existed in the past. This is an important indicator of livability.
An accidental trajectory the spacecraft charted on the Vera Rubin ridge in 2019 made it possible to study the mudstone layer that formed in a lake about 3.5 billion years ago.
Curiosity collected soil samples from two sites less than 400 meters apart.
The mudstones in both areas belonged to the same time and the same region. Therefore, it was expected to contain similar amounts of clay minerals. But one piece of land contained only half the expected amount of minerals.
This startling observation required researchers led by Tom Bristow of NASA’s Ames Research Center to explain the missing clay.
The team speculated that the most likely explanation is water seeping into the clay layer from a sulfate deposit found above. Accordingly, extremely salty water had seeped through the grains of sand at the bottom of the old lake and replaced the mineral-rich layers below.
“We used to think that these clay mineral layers that formed at the bottom of the lake in Gale Crater remained that way and maintained the conditions they formed for billions of years,” Bristow said.
But then the salty waters in some places degraded these clay minerals and essentially reset the records in the rocks.
After the lake dried up, groundwater in the island’s Gale crater continued to carry and dissolve chemicals below the surface, according to the researchers. As a result, some mudstone areas were exposed to different conditions.
These saltwater-exposed areas went through a process called “diagenesis,” in which changing mineralogy erased the geological and possibly biological record. Diagenesis means the transformation of sedimentary rocks into different metamorphosed sedimentary rocks under the influence of temperature and pressure.
On the other hand, according to John Grotzinger, professor of geology at the California Institute of Technology and co-author of the study, diagenesis can create environments that are friendly to microscopic creatures, even though it has erased potential evidence of life.
“These are excellent places to look for evidence of ancient life and measure habitability,” Grotzinger said in a statement.
Diagenesis can erase any signs of life in the original lake, but it also creates the chemical gradients necessary to support underground life. So we’re really excited to discover this.
Source: The Independent
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