There’s Proof That Mars As soon as Had an Ambiance With Much less Oxygen. A Potential Biosignature For Life?

There's Evidence That Mars Once Had an Atmosphere With Less Oxygen. A Possible Biosignature For Life?

Remote sensing is only useful when scientists have an idea of ​​what they are looking at. This knowledge is particularly important for remote sensing applications on other planets such as Mars, where it is extremely difficult to collect information about an observed object in any other way. To compensate for the inability to conduct other tests on site, scientists conducted laboratory experiments with different environments and materials and compared the remote sensing data with the remote objects observed.

That is exactly what Jiacheng Liu, a PhD student at the University of Hong Kong, did with remote sensing data from the Martian surface. What he found gave new weight to a novel theory – that Mars previously did not have a significant amount of oxygen in its atmosphere. The fact that it is now raises the question of where all of the oxygen in the atmosphere today comes from. One possible answer is the same place on earth – photosynthetic life.

UT video about the Martian atmosphere.

Mars is commonly referred to as the “red planet” because most of its surface is covered in iron oxide, commonly known as rust, which is a red hue. Not all parts of the planets are red, however – there are some volcanic rocks that do not contain a lot of iron and therefore are not subject to the oxidation reaction that covers so much of the rest of the planet.

The same volcanic rocks are also revealing windows into Mars’ atmospheric chemistry that is unaffected by oxygen. Dr. Liu discovered that the development of basalt and other minerals on the island of Hainan in southwest China were good proxy for the exposed volcanic rock on Mars.

Remote sensing image showing the clays, including the iron-rich, non-oxidized ones that were recently exposed to the Martian atmosphere.
Photo credit: University of Hong Kong

What is important is that this exposed rock on Mars was old and last would have interacted with the Martian atmosphere billions of years ago. Its structure showed that it was last exposed to an environment that did not contain much oxygen, as the iron contained in the rocks had not yet oxidized.

Such an oxygen-poor environment also existed on Earth billions of years ago. Then, about 2.5 billion years ago, there was a switch to an oxygen-rich atmosphere, known as the Great Oxidation Event. Scientists believe that the impetus for this transition was the multicellular life that photosynthesized and replenished oxygen in the atmosphere as it was also trapped in iron oxide.

Image of Mar's surface from the Viking Orbiter.The image was taken by the Viking 1 orbiter in June 1976 and shows the thin Martian atmosphere and the dusty, red surface. Credits: NASA / Viking 1

So far there has been no such explanation as to why the Martian atmosphere gained so much oxygen. There are non-biological processes that could be responsible for such a transition. But it opens up the tantalizing possibility that long ago when Mars was warmer and more humid, Mars experienced an explosion of life that caused its atmosphere to change to what it is today. However, as with so much other scientific evidence, more data is needed because “exceptional claims require exceptional evidence”.

Learn more:
UHK: Planetary researchers discover evidence of a reduced atmosphere on ancient Mars
UT: What’s the atmosphere like on Mars?
Syfy: Mars may look like an alien wasteland, but we now have more evidence that it might once have been a different earth

Mission statement:
Layers on Mars showing iron-rich rocks (blue) that have long been buried next to longer-exposed rocks (yellow).
Photo credit: University of Hong Kong

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