Photo credit: arstechnica.com
The Curiosity rover’s mission commenced at the lower reaches of Gale Crater, specifically at the base of Mount Sharp, also known as Aeolis Mons. NASA’s initial expectation was to uncover some of the oldest geological samples in this region. The strategy involved a meticulous ascent of Mount Sharp, collecting evidence from progressively younger geological layers as the rover advanced, thereby mapping Mars’ history of habitability and the planet’s transition to its current arid state. During this journey, Curiosity discovered carbon that had previously eluded satellite observations.
A Complex Carbon Cycle
Researchers, led by Tutolo, concentrated on four sediment samples that the Curiosity rover extracted after journeying over a kilometer up Mount Sharp. These samples underwent analysis using the rover’s Chemistry and Mineralogy instrument, which employs X-ray diffraction to identify mineral compositions. The findings revealed that the samples contained approximately 5 to 10 percent siderite, an iron carbonate mineral analogous to calcite found in terrestrial sedimentary rocks like limestone. “Siderite contains iron instead of calcium, which aligns with the composition of Mars, as the planet is rich in iron—and hence its distinctive red hue,” Tutolo clarified.
The purity of the siderite detected in these samples led Tutolo to theorize that it formed through an evaporation process similar to what is observed in Earth’s evaporated lakes. This discovery serves as the first confirmation of an ancient carbon cycle on Mars. “We now have tangible evidence supporting the theoretical models,” Tutolo stated, pointing out that atmospheric carbon was being sequestered in Martian rocks parallel to processes seen on Earth. However, a significant difference lies in the fate of the carbon: while Earth has mechanisms to release this carbon back into the atmosphere, Mars does not.
“On our planet, subducted oceanic plates lead to the recycling of limestone into the mantle, allowing carbon dioxide to re-enter the atmosphere via volcanic activity,” Tutolo explained further. In contrast, Mars has historically lacked effective plate tectonics, resulting in a substantial proportion of carbon becoming permanently integrated within Martian rocks. This geological quirk significantly contributed to the thinning of Mars’ atmosphere, suggesting that while the planet may have had its own carbon cycle, it was flawed—ultimately leading to its current desiccated and barren landscape.
Source
arstechnica.com