Newly published research quantifies the presence of organic carbon in the rocks of Mars. For the first time, scientists using data from NASA’s Curiosity rover measured total organic carbon – a key component in life molecules – on the rocks of Mars. “Total organic carbon is one of the many measurements [or indices] “They help us understand how much material is available as a raw material for prebiotic chemistry and possibly biology,” said Jennifer Stern of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We found at least 200 to 273 parts per million of organic carbon. “This is comparable or even greater than the amount found in rocks in places with very low life on Earth, such as parts of the Atacama Desert in South America, and more than what has been detected in Mars meteorites.” Organic carbon is carbon attached to a hydrogen atom. It is the foundation for organic molecules, which are created and used by all known life forms. However, because organic carbon can also come from non-living sources, its presence on Mars does not prove the existence of life there. For example, it may come from meteorites, volcanoes, or be formed in its place by surface reactions. Organic carbon had been found on Mars in the past, but previous measurements produced information only for specific compounds or represented measurements that capture only part of the carbon in rocks. The new measurement gives the total amount of organic carbon present in these rocks. NASA’s Curiosity Mars rover used its History Camera, or Mastcam, to capture this area on the edge of a site nicknamed “Yellowknife Bay.” The image is a combination of three mosaics taken on December 24, 25 and 28, 2012 (the 137th, 138th and 141st Martian day, or sols, of the mission). Credit: NASA / JPL-Caltech / MSSS Although the surface of Mars is currently inhospitable to life, there are indications that billions of years ago the climate was more like Earth, with a thicker atmosphere and liquid water flowing in rivers and seas. Since water in liquid form is essential for life as we understand it, scientists believe that life on Mars, if it had ever evolved, could have been maintained by key ingredients such as organic carbon, if it had existed in sufficient quantity. Curiosity promotes the field of astrobiology by researching the habitability of Mars, studying its climate and geology. The rover drilled samples of 3.5 billion-year-old mudstones into the “Yellowknife Bay” formation of Gale Crater, the site of an ancient lake on Mars. The mudstone in the Gale Crater formed as a very fine sediment (from the physical and chemical erosion of volcanic rocks) in water that settled to the bottom of a lake and was buried. Organic carbon was part of this material and was incorporated into the mudstone. In addition to liquid water and organic carbon, Gale Crater had other life-threatening conditions, such as chemical energy sources, low acidity, and other elements necessary for biology, such as oxygen, nitrogen, and sulfur. “Basically, this site would provide a habitable environment for living, if it ever existed,” said Stern, lead author of a paper on this research published June 27 in the Proceedings of the National Academy of Sciences. NASA’s Curiosity rover for Mars used its left Navigation Camera to capture this view of the staircase in a shallow cavity called the “Yellowknife Bay.” The descent into the basin crossed a step about 2 feet high, visible in the upper half of this image. NASA’s Curiosity Mars rover used the Navigation Camera to capture this view after entering a site nicknamed “Yellowknife Bay” on December 12, 2012, the 125th Martian Day, or sol, of the mission. Credit: NASA / JPL-Caltech To perform the measurement, Curiosity delivered the sample to the Sample Analysis at Mars (SAM) instrument, where an oven heated the pulverized rock to progressively higher temperatures. This experiment used oxygen and heat to convert organic carbon to carbon dioxide (CO2), the amount of which is measured to obtain the amount of organic carbon in rocks. The addition of oxygen and heat allows carbon molecules to decompose and react carbon with oxygen to create CO2. Some carbon is locked in minerals, so the furnace heats the sample to very high temperatures to decompose these minerals and release the carbon to convert it to CO2. The experiment took place in 2014 but it took years of analysis to understand the data and put the results in the context of the other discoveries of the Gale crater mission. The resource-intensity experiment was performed only once during the 10 years of Curiosity on Mars. This process also allowed SAM to measure carbon isotope ratios, which help to understand the carbon source. Isotopes are versions of an element with slightly different weights (masses) due to the presence of one or more additional neutrons in the center (nucleus) of their atoms. For example, carbon-12 has six neutrons while heavier carbon-13 has seven neutrons. As heavier isotopes tend to react a little slower than lighter isotopes, the carbon from life is richer in carbon-12. “In this case, the isotopic composition can really only tell us which part of the total carbon is organic carbon and which part is mineral carbon,” Stern said. “While biology cannot be completely ruled out, isotopes cannot really be used to support the biological origin of this carbon, because the range overlaps with volcanic carbon and meteoric organic material, which is very likely to be the source. his. organic carbon “. The research was funded by NASA’s Mars Exploration Program. Curiosity’s mission to Mars Science Laboratory is led by NASA’s Jet Propulsion Laboratory in Southern California. JPL is managed by Caltech. The SAM was built and tested at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Charles Malespin is the lead researcher at SAM.
