The NASA Curiosity Rover has been exploring Mars for many years. One of the key experiments that the rover has been conducting is a multi-year experiment happening in the chemistry lab inside the rover’s belly called the Sample Analysis at Mars (SAM). Scientists have used the results of that test to make insights into answering some of the biggest questions about Mars, such as are there organic compounds, if the planet had liquid water, and could it have supported life in the distant past.
The team of scientists studying the results of the Curiosity experiment has found that certain minerals in the rocks at Gale Crater may have formed in an ice-covered lake. Scientists believe that the minerals may have formed during a cold stage between warmer periods or after Mars lost most of its atmosphere and began to turn permanently cold. Gale Crater is the location where Curiosity landed in 2012 and is massive at the size of Connecticut and Rhode Island combined.
That site was chosen due to signs of past water, including clay minerals that might help trap and preserve ancient organic molecules. While some of the features in crater hint at a planet that was warm and humid for millions of years, other geological features in the crater hint at a past that included cold and icy conditions. When exactly the surface of Mars transitioned from warm and humid to cold and dry as it is now is a key question scientist want to answer.
The scientists found evidence for a cold ancient environment after the SAM lab extracted gases carbon dioxide and oxygen from 13 dust and rock samples collected over five Earth years. Scientists are finding there’s a carbon lifecycle on Mars and are working to understand it.
Studies have suggested that the ancient Martian atmosphere contained mostly carbon dioxide and could have been thicker than the atmosphere the Earth has today. When SAM heated the specimens and liberated gases inside of them, scientists can look at temperatures that released CO2 and oxygen to tell what minerals the gases were coming from to understand the carbon cycle on Mars. The carbonates that were discovered are believed to have been formed in a freezing lake because the oxygen isotopes are lighter than those in the Martian atmosphere today.