Lake County News, California – Space News: NASA’s Curiosity takes inventory of a key ingredient for life on Mars

From a position in the shallow “Yellowknife Bay” depression, NASA’s Curiosity rover used its upright mast camera (Mastcam) to capture the combined telephoto images in this panorama of geological diversity. Credits: NASA/JPL-Caltech/MSSS.

Scientists using data from NASA’s Curiosity rover have measured total organic carbon – a key component of life’s molecules – in Martian rocks for the first time.

“Total organic carbon is one of the measures [or indices] that help us understand how much material is available as feedstock for prebiotic chemistry and potentially 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 more than the amount found in rocks in very low-lived places on Earth, such as parts of the Atacama Desert in South America, and more than has been detected in meteorites. Of March.

Organic carbon is carbon bonded to a hydrogen atom. It is the basis of organic molecules, which are created and used by all known life forms.

However, organic carbon on Mars does not prove the existence of life there because it can also come from non-living sources, such as meteorites and volcanoes, or be formed on site by surface reactions.

Organic carbon has been found on Mars before, but earlier measurements only yielded information about particular compounds or represented measurements capturing only part of the carbon in rocks. The new measurement gives the total amount of organic carbon in these rocks.

Although the surface of Mars is now inhospitable to life, there is evidence that billions of years ago the climate was more Earth-like, with a thicker atmosphere and water liquid that flowed in rivers and seas.

Since liquid water is necessary for life as we understand it, scientists believe that Martian life, if it had ever evolved, could have been supported by key ingredients such as organic carbon, if it were. present in sufficient quantities.

Curiosity advances the field of astrobiology by studying the habitability of Mars, studying its climate and geology.

The rover drilled samples of 3.5 billion-year-old mudstone rock from the Yellowknife Bay Formation of Gale Crater, the site of an ancient lake on Mars. The Gale Crater mudstone formed as very fine sediments (resulting from the physical and chemical weathering of volcanic rocks) in water deposited at 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 conditions for life, such as chemical energy sources, low acidity, and other essential elements for biology, such as oxygen. , nitrogen and sulfur.

NASA’s Mars Curiosity rover used its left navigation camera to record this view of the descent into a shallow depression called “Yellowknife Bay.” He took the image on the 125th Martian day, or sol, of the mission (December 12, 2012), just after completing the journey from that sol. Credits: NASA/JPL-Caltech.

“Basically, this place would have provided a habitable environment for life, had it ever been present,” said Stern, lead author of a paper on the research published June 27 in the Proceedings of the National Academy of Sciences. .

To make the measurement, Curiosity delivered the sample to its Sample Analysis at Mars instrument, OR SAM, where a furnace heated the rock powder to progressively higher temperatures.

This experiment used oxygen and heat to convert organic carbon into carbon dioxide, or CO2, the amount of which is measured to get the amount of organic carbon in rocks.

The addition of oxygen and heat allows carbon molecules to split apart and react carbon with oxygen to produce CO2. Some of the carbon is trapped in the minerals, so the furnace heats the sample to very high temperatures to break down these minerals and release the carbon to convert it to CO2.

The experiment was performed in 2014 but took years of analysis to understand the data and put the results in context with the mission’s other findings at Gale Crater. The resource-intensive experiment has only been performed once in Curiosity’s 10 years on Mars.

This process also allowed SAM to measure carbon isotope ratios, which helps to understand the source of the carbon. Isotopes are versions of an element with slightly different weights (masses) due to the presence of one or more extra neutrons in the center (nucleus) of their atoms.

For example, carbon 12 has six neutrons while the heavier carbon 13 has seven neutrons. Since heavier isotopes tend to react somewhat slower than lighter isotopes, the carbon of life is richer in carbon-12.

“In this case, the isotopic composition can only really 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 also cannot really be used to support a biological origin for this carbon, since the range overlaps igneous (volcanic) carbon and meteoritic organic matter, which are the more likely to be the source of that carbon. organic carbon.”

The research was funded by NASA’s Mars Exploration Program. Curiosity’s Mars Science Laboratory mission is led by NASA’s Jet Propulsion Laboratory in Southern California; The JPL is managed by Caltech. SAM was built and tested at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Charles Malespin is the Principal Investigator of SAM.

Bill Steigerwald works for NASA’s Goddard Space Flight Center in Greenbelt, Maryland.