Most people will think of a dry, arid landscape when they think of Mars. From orbit, dry river channels and lakebeds can be seen, as well as mineral deposits thought to have been formed by the presence of liquid water. A team of researchers now suggests that liquid carbon dioxide could also explain the observed features. On Earth, a process known as carbon sequestration liquefies CO2 that is buried underground. There are a number of mechanisms that could explain the liquid CO2 underground, the researchers suggest.
Because of its visual appearance, Mars is often referred to as the “Red Planet”. It is the fourth planet from the sun and has been a real focus of research and research for decades. The red color is caused by iron oxide (rust) on its surface, which is often lifted into the atmosphere by the Martian winds, creating stunning pink skies. It is just over half the size of Earth, has a thin atmosphere made up mostly of carbon dioxide, and a surface made up of deserts and volcanoes like Olympus Mons. One of the main focuses of Mars exploration has been to determine whether the conditions are suitable for life, have been suitable in the past, or whether liquid water is present on the surface.
A full disk view of Mars, courtesy of VMC. Photo credit: ESA
The presence of dry river and lake beds suggests a surface where fluid flowed long ago. Exactly what this liquid is has been a source of debate. Observations of minerals from orbit and more direct analysis on the surface suggest that the liquid was simply water. However, a team of researchers has published a paper in Nature Geoscience that suggests otherwise. They explain that water is only one of two possible liquids that could have existed on ancient Mars. The other is liquid carbon dioxide or CO2. Given the atmospheric conditions, it may have been more likely and easier for CO2 in the atmosphere to condense into a liquid than for surface ice to melt into water.
A topographic image of an area of former riverbeds on Mars. Created using data from the Mars Express Orbiter's high-resolution stereo camera. Image source: ESA/DLR/FU Berlin http://www.esa.int/spaceinimages/ESA_Multimedia/Copyright_Notice_Images
There is general consensus that the minerals indicate liquid water. The paper suggests that processes such as carbon sequestration and liquid CO2 underground can change the composition of minerals even faster than water. Lead author Michael Hecht, a research scientist at MIT's Haystack Observatory, said: “Understanding how sufficient liquid water could flow on early Mars to explain the morphology and mineralogy we see today is probably the biggest unanswered question of the planet.” Mars science. “There is probably no right answer and we are simply suggesting another possible piece of the puzzle.”
Image of the Martian atmosphere and surface taken by the Viking 1 orbiter in June 1976. (Source: NASA/Viking 1)
The article examines our current understanding of the Martian atmosphere and combines it with research on carbon sequestration to conclude that the processes support the evidence and mineralogy observed on Mars. However, they note that this suggestion does not suggest that all of Mars' surface liquid was CO2, but rather that there may have been a combination of the two.
They explain that liquid CO2 could exist on the Martian surface as a stable surface liquid, as molten CO2 under CO2 ice, or in underground reservoirs. What actually took place depended entirely on the CO2 distribution at the time and also on the surface conditions. The paper acknowledges that further testing under more realistic Martian conditions is needed to test whether the same processes still occur.
Source: The liquid on Mars wasn't necessarily just water
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