Mars: key element of life quantified for the first time
By analyzing data from NASA’s Curiosity rover, a team of researchers was able to measure the amount of total organic carbon in the rocks of Mars. It is the first time that we have a full estimate of the presence of this key component in the molecules of life on the Red Planet. Researchers were already aware of the presence of organic carbon on Mars, but the total amount of organic carbon present in rocks had never been calculated before.
The abundance of the life molecule on Mars
As Jennifer Stern, of NASA’s Goddard Space Flight Center in Greenbelt, Maryland explains, “Total organic carbon is one of several measurements that help us understand how much material is available as feedstock for prebiotic chemistry and potentially biology. We found 200 to 273 parts per million of organic carbon. This is comparable to or even greater than the amount found in rocks in very low-life places on Earth, such as parts of the Atacama Desert in South America, and more than has been found in Mars meteorites. “
Organic carbon is the building block for organic molecules, which are created and used by all known life forms. It is carbon bonded to a hydrogen atom. Unfortunately, its existence on Mars alone is not sufficient to demonstrate that there is, or has been, life on the Red Planet. In fact, this molecule can come from even from non-living sourcessuch as meteorites, volcanoes or surface reactions.
But, even if it does not prove that there was life on Mars, the presence of sufficient organic carbon on Mars demonstrates that if Martian life had ever evolved, it could have been supported by key ingredients such as organic carbon. Although the Martian surface now seems to us the most inhospitable place for life, we know that billions of years ago the climate was more like that of Earth, with a denser atmosphere and liquid water flowing into rivers and seas. Under such conditions a sufficient presence of organic carbon it could have kept any traces of life.
Curiosity’s perforations and analyzes
Curiosity is conducting its research in the field of astrobiology by studying the habitability of Mars, climate and geology. To conduct its research, the rover drilled samples from muddy rocks dating back to approx 3.5 billion years in training “Yellowknife Bay” of the Gale Crater, the site of an ancient lake on Mars.
In addition to liquid water and organic carbon, the Gale crater featured other conditions favorable to life, such as sources of chemical energy, low acidity, and other essential elements for biologysuch as oxygen, nitrogen and sulfur.
To make its measurements on organic carbon, Curiosity analyzed the sample from the bore with its instrument Sample Analysis at Mars (SAM). This tool used oxygen and heat to convert organic carbon into carbon dioxide. By then measuring the amount of CO2 emitted, the estimate of the amount of organic carbon in the rocks taken by Curiosity was obtained. The experiment was conducted in 2014 but required years of analysis to understand the data and put the findings in the context of the other findings of the mission to the Gale Crater.
This process also allowed SAM to measure the isotope ratios of carbon, which help to understand the source of the carbon. Indeed, as Stern explains, “the isotopic composition can tell us which part of the total carbon is organic carbon and which part is mineral carbon. But, although biology cannot be completely ruled out, isotopes cannot be used for either support a biological origin for carbon. “
Ph. Credit: Nasa / Jpl-Caltech / Asu, Nasa / Jpl-Caltech / Univ. of Arizona and Scott Rowland, Nasa Jpl-Caltech / Msss