Since landing in 2012, the Curiosity rover has been collecting samples from the Martian surface as part of its ambitious search for life mission. Now, after analyzing those sediments, NASA has announced the detection of a type of carbon that is associated with biological processes on Earth.
The finding is intriguing because carbon is the chemical basis of life on our planet, yet Mars is so different that the same environmental, chemical, and physical rules don’t apply. In consecuense, Scientists have developed three hypotheses that attempt to explain this phenomenon: one biological, inspired by terrestrial life, and two non-biological.
What are the carbon hypotheses on Mars?
The biological hypothesis says that a series of ancient bacteria located on the surface of Mars produced a unique carbon footprint product of the release of methane from the soil into the atmosphere. After this process, the scientists explain, the ultraviolet light transformed the gas into larger and more complex molecules that were later deposited on the surface and preserved in the Martian rocks.
One of the non-biological hypotheses suggests that the carbon footprint could have resulted from the interaction of ultraviolet light with carbon dioxide gas in the Martian atmosphere. This had produced new molecules containing the carbon that would have settled on the surface.
The other says that the carbon could be the result of an event millions of years ago in which the Solar System passed through a galactic molecular cloud on its last transit of the inner planets. A hypothetical Mars in which there was water would have cooled and part of the carbon in the cloud would have been deposited on the planet’s glaciers.
All three explanations fit the data. dice Christopher House, a Curiosity scientist at Penn State headquarters who led the carbon study. However, he points out that more data is needed to rule out and that at the moment no conclusive evidence of ancient biological presence on Mars has been found.
For his part, former Sample Analysis at Mars (SAM) chemistry lab researcher Paul Mahaffy says: “We’re finding things on Mars that are tantalizingly interesting, but we really need more evidence to support that we’ve identified life.”
How were the samples analyzed?
If all goes as planned, Perseverance will bring back to Earth a series of rock samples she has collected. Meanwhile, we can remotely analyze the martian surface thanks to the Sample Analysis at Mars (SAM) chemistry lab aboard Curiosity.
SAM used its Tunable Laser Spectrometer (TLS) instrument to heat the 24 samples collected over the past few years to about 850 degrees Celsius. heating product, Carbon isotopes were measured, revealing the existence of carbon-12 and carbon-13.
Carbon is one of the most abundant elements in the universe.. On Earth it flows through air, water, and soil thanks to the carbon cycle, but what is carbon-12 and carbon-13? To understand it, we must remember what isotopes are.
Isotopes are atoms that they have the same number of protons but different numbers of neutrons. Since the atomic number is equal to the number of protons, and the atomic mass is the sum of protons and neutrons, isotopes have different mass numbers.
For example, carbon-12 is the most abundant of the stable isotopes of carbon. It is made up of 6 protons, 6 neutrons and 6 electrons, and is the basis for living beings on Earth to metabolize food or for photosynthesis.
Carbon-13, meanwhile, contains 6 protons and 7 neutrons, making up only 1.1% of all carbon on Earth. Observing the ratio of these two carbon isotopes helps scientists to know what kind of life they are observing on Earth.
But this model is complicated to apply on Mars. The planet may have originated with a different mix of carbon isotopes than on Earth. Being a smaller, colder planet with weaker gravity, this chemical element may not be associated with life.
However, these latest findings will serve to better understand what the unusual carbon cycles are like on the red planet and, eventually, to know whether the identified carbon footprints are evidence that there was once life or not on the red planet..
More information | NASA