Scientists have found a plausible explanation for how Mars has lost its atmosphere, after discoveries showing that the Red Planet might have had an atmosphere even thicker than Earth’s.
Researchers now believe that Mars has once been a warm and watery planet, with a thick atmosphere. However until now there was no explanation for how did that change, transforming the planet into the cold, dry place that it is today.
A possible explanation has been formulated by a team of scientists from NASA’s Jet Propulsion Laboratory (JPL) and California Institute of Technology.
They think that they discovered a photochemical process that could have made the dense atmosphere Mars once had to evolve to the one it has now by removing the excess of carbon dioxide.
They formulated two different scenarios. One is that the carbon dioxide had been incorporated into rocks as what is called carbonates. The other possible scenario is that the carbon dioxide has been lost in space.
However, a previous study has shown that the upper layer of Martian surface doesn’t contain such a high quantity of carbon as it would require for the theory to be validated.
To verify the theory of the carbon dioxide being lost in space, scientists start measuring carbon-12 and carbon-13. These are two carbon isotopes with the same number of protons but a different mass.
Chemical processes are generally able of changing the amounts of the two isotopes. Researchers start measuring their ratio at different times in the far history of Mars’ existence, using meteorites from its surface that contain gases from the planet’s mantle. Comparing the findings from the present and the past, scientists have been able to conclude that the ratio of carbon-13 in the Red Planet’s atmosphere is unusually high.
The theory of the solar winds ripping off Mar’s atmosphere – called Sputtering – has been ruled off since the scientists believe that their effect wouldn’t have enough strength to create such an enormous deficit of carbon.
However, the last theory of Caltech and JPL might be the most concluding. They argue that a chemical process between the CO2 and the ultraviolet light could be involved. When hit by UV molecules of CO2 raise to the superior part of the atmosphere. There, its molecule absorbs the energy of the photon and divides into carbon monoxide (CO) and oxygen (O). When another UV strikes the CO, it is finally divided into carbon (C) and oxygen (O). The carbon produced by this chemical process can have enough energy to escape the atmosphere.
The study also shows that carbon-13 isotopes escape harder than carbon-12, which can explain their higher presence. This is in accordance with the findings of NASA’s Curiosity rover in the Martian atmosphere.
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