In June of 2012, the high-resolution stereo camera on Mars Express exploration probe recorded the area with bright spots resembling a surface covered with snow on the Red Planet near Charitum Montes, a large group of rugged mountains near the Gale crater and the Argyre basin. Recently scientists discovered that this effect is produced by frozen carbon dioxide.
The area is a fairly large group of rugged mountains stretching for 1,000 kilometers along the southern tip of the Argyre crater. They were first described in 1929 by Eugène Michel Antoniadi. They can be seen from the Earth through a large telescope.
To a terrestrial observer the mountains look like a terrain with old relief, including larger forms and nearly covered with craters of an impressive size. Smaller craters in the shape of pedestals are significantly more numerous. They emerge during the formation of the elevated landscape. The material in such places is resistant to erosion, and the rock is destroyed slower than in the immediate environment, hence the elevations.
Carbon dioxide that adds brightness to the Martian surface in this area is better known as carbon dioxide that we exhale into the atmosphere. On Earth it enters the underground structures of the soil and is formed by decomposition of organic matter in various reservoirs, tanks, silos and similar areas that provide for slow oxidation reaction of carbon. In addition, it is found in spring water. In household carbon dioxide is used in firefighting as it reduces concentration of oxygen in the air, making it difficult to burn. Incidentally, foam extinguishers look like snow.
How did carbon dioxide appear on Mars? First of all, this is another reason to talk about the habitability of the Red Planet, or the fact that it was once inhabited. We can say that its residents, just as humans, once inhaled oxygen and exhaled CO2. Then the climate of the planet changed, the Martians have disappeared, and the gas froze and settled on the surface.
Water was also found on Mars. Back in 2006, MARSIS radar revealed vast accumulation of water ice beneath the surface. In particular, a crater with a diameter of approximately 250 km beneath Chryse Planitia is filled with ice. Last year, experts from Germany found tracks similar to those left by canals on the slopes of a Martian canyon located in the region of Melas Chasma. At the bottom of the canals they found sulfate compounds that are usually formed from oxidation by water. This led to the conclusion that there was once a large sea in the area. Recently, researchers examined the images obtained with telemetry rover Curiosity and saw a gravel bed of a river or stream, covered with rocks.
It is located between a field to the north of the crater and the foot of a mountain. According to experts, the size and shape of the rocks on the bed give an idea of what the length of the river and the rate of water flowing into it were. If it turns out that the material includes clay and sulfates that can theoretically contain elements of organic matter, it would mean that, theoretically, life could exist on the planet.
Yet so far no microbes have been found on Mars. Besides, laser spectrometer Curiosity never recorded methane traces in the Martian atmosphere traditionally believed to be one of the main signs of presence of living organisms.
As for the presence of carbon, not that long ago a team of astronomers from the Carnegie Institute for Science in Washington, DC led by Andrew Steele discovered that the organic molecules found in Martian meteorites that have geological origin were not brought here from Earth or deep space. According to the scientists, microscopic beads of molten silicon rocks within meteorite fragments indicate their origin as a result of volcanic activity or other geological phenomena, but not biological processes.
While another discovery of specialists is an interesting surprise, it is worth remembering that Mars, being considered officially an Earth-like planet, is too different from Earth. It has different geological composition, the composition of the atmosphere and climatic conditions. So far nothing brings us closer to the evidence that there was once life on that planet.