Scientists have found diverse minerals on Mars, suggesting that conditions changed on the planet over time.
This was unveiled after scientists examining initial samples collected by NASA's Curiosity rover from rocks in the lowermost layers of a Martian mountain dabbed Mount Sharp.
Curiosity landed near Mount Sharp in the Gale Crater in August 2012 and reached the base of the mountain in 2014. It began to drive toward uphill destinations on Mount Sharp since its second two-year mission extension commenced on Oct. 1, 2016.
In a paper published recently in Earth and Planetary Science Letters, scientists from the Astromaterials Research and Exploration Science (ARES) Division at NASA's Johnson Space Center reported the first four samples collected from the lower layers of Mount Sharp.
"We went to Gale Crater to investigate these lower layers of Mount Sharp that have these minerals that precipitated from water and suggest different environments," Elizabeth Rampe, lead author of the new study and a NASA exploration mission scientist at Johnson Space Center, said in a press statement.
"These layers were deposited about 3.5 billion years ago, coinciding with a time on Earth when life was beginning to take hold. We think early Mars may have been similar to early Earth, and so these environments might have been habitable," Rampe said.
The team said that the minerals found in the four samples drilled near the base of Mount Sharp suggest several different environments were present in ancient Gale Crater. There is evidence for waters with different pH levels and other varying conditions.
Studying such rock layers can yield information about Mars' past habitability, and determining minerals found in the layers of sedimentary rock yields much data about the environment in which they formed.
According to the U.S. space agency, at the base are minerals from a primitive magma source; they are rich in iron and magnesium, similar to basalts in Hawaii. Moving higher in the section, scientists saw more silica-rich minerals. In the "Telegraph Peak" sample, scientists found minerals similar to quartz.
In the "Buckskin" sample, scientists even found a mineral called tridymite, which was somewhat perplexing. Tridymite is found on Earth in rocks that formed from partial melting of Earth's crust or in the continental crust -- a strange finding because Mars never had plate tectonics.
That's not all. Scientists found clay minerals in the "Confidence Hills" and "Mojave 2" samples. The minerals generally form in the presence of liquid water with a near-neutral pH, and therefore could be good indicators of past environments that were conducive to life.
The other mineral discovered here was jarosite, which "indicates that there were acidic fluids at some point in time in this region."
In addition, there are different iron-oxide minerals in the samples as well. The presence of hematite, found near the base, and magnetite, found at the top, may tell scientists about the oxidation potential of the ancient waters.
"We have all this evidence that Mars was once really wet but now is dry and cold," Rampe said.
"Today, much of the water is locked up in the poles and in the ground at high latitudes as ice. We think that the rocks Curiosity has studied reveal ancient environmental changes that occurred as Mars started to lose its atmosphere and water was lost to space," Rampe added.
Data gathered by Curiosity over the past five years have allowed scientists to construct a detailed portrait of the history of Gale Crater and the lowermost layers of Mount Sharp where the rover had been traversing.
Mineral samples collected with the Chemistry and Mineralogy instrument on the rover have shown very diverse environments over the history of the Red Planet.
With the help of orbital infrared spectroscopy, it was found that the mountain's lowermost layers had variations in minerals.