Universe Today
Planetary scientists have plenty of theories about Mars and its environmental past. Two of the most widely accepted are that there was a carbon dioxide atmosphere and, at one point, liquid water on Mars' surface. However, this theory has a glaring problem: Where should the rocks have formed from the interactions between carbon dioxide and water? According to a new paper by scientists at several NASA facilities using data collected by the rover Curiosity, the answer is right under the rover's metaphorical feet.
According to geology, carbon dioxide and water should react together to form "carbonates," a type of mineral that contains an ion made up of carbon and oxygen. This process is relatively common on Earth and even in some manufacturing processes, but the results have never before been seen on Mars, at least not in any quantity.
That is despite a significant amount of effort spent looking for them. Rovers have looked for them to no avail. Even satellites have done spectroscopy on most of the planet and haven't seen anything that could be a carbonate anywhere near the quantities to prove that Mars had an atmosphere of carbon dioxide and liquid water at one time. That was, until the little rover that could stepped in.
Curiosity has had a hand in plenty of important discoveries on the Red Planet. Here's a video from Fraser 7 years ago that discusses some of them.
Curiosity has dug holes throughout Mars' Gale Crater for almost 13 years. During that time, some significant discoveries were made, but this latest one has dramatically impacted our understanding of the evolution of the Martian climate. At three different drill sites around Mount Sharp, Curiosity found evidence for a mineral called siderite, a carbonate material formed with iron.
Siderite itself wasn't present on the surface, though. It was only found when Curiosity drilled down 3-4cm into the surface of a rock and analyzed the resulting drill powder in its CheMin instrument. After the instruments zapped it with X-rays, the researchers found the presence of the elusive mineral that could explain where Mars' atmosphere went, at least partially.
The presence of carbonates under layers of other rock could also explain why they have been so hard to find up until now. Orbiting satellites wouldn't be able to see a few centimeters into existing rock, and most rover spectroscopy is done without drilling into a sample, so they wouldn't have been able to detect it either. But finding any does lend credence to the idea that Mars used to be habitable for basic microorganisms, at one point at least.
Here's a look back at Curiosity's first science target - Jake the Rock.
Scientists from several different NASA centers, including the Jet Propulsion Laboratory (Curiosity operation), Ames Research Center (CheMin Instrument operation), and John Space Center (data analysis) contributed to the work. According to Benjamin Tutolo, a professor at the University of Calgary, "the discovery of abundant siderite in Gale Crater represents both a surprising and important breakthrough in our understanding of the geologic and atmospheric evolution of Mars."
It certainly does, though the estimated amount of siderite and other carbonates based on this newest data isn't enough to explain where all of Mars' atmosphere went. There could be other, more abundant hiding places, or the Red Planet could have lost its atmosphere slowly over time due to the solar wind, since it has lacked a magnetic field for so long. As rovers continue to explore its surface, a steady stream of new findings will continue to intrigue planetary scientists, and hopefully help them refine their theories on how Mars came to be what it is today.
Learn More:
NASA / JPL - NASA’s Curiosity Rover May Have Solved Mars’ Missing Carbonate Mystery
Tutolo et al - Carbonates identified by the Curiosity rover indicate a carbon cycle operated on ancient Mars
UT - Could There Be Bacteria Living on Mars Today?
UT - It's Not Just Rocks, Scientists Want Samples Mars's Atmosphere
