It was recently discovered by scientists that the Red Planet, Mars, is quite peculiar in that towards its southern hemisphere, nearer its southern pole, it snows, but unlike the usually water-based snow that we see on Earth, it snows carbon dioxide on Mars. Known to have frozen carbon dioxide on its surface, Mars was seen, through data collected by satellites, to snow CO2 during the winter months, with CO2 snow clouds forming and regular CO2 snowfall and accretion on its surface. Of course, how this happens is not known, but at the time of its discovery, it was assumed that this type of snowfall was particularly unique to Mars, but now it seems that European scientists have discovered signs of CO2 snowfall on another planet in the solar system, Venus.
Using the European Space Agency's Venus Express satellite, researchers have observed a cold spot in the higher climes of the planet, where it is likely to be cold enough for carbon dioxide to freeze and as a result lead to CO2 snowfall.
Venus itself is otherwise known to be quite hot, seeing as how close it is to the sun, but using the Venus Express satellite, scientists noted a particularly cold region in the planet’s atmosphere and being almost entirely enveloped in a CO2-rich atmosphere, it was likely that because of this cold region, the CO2 in the atmosphere could actually solidify and freeze, leading to possible CO2 snowfall.
The Venus Express detected the cold region some 125 kilometers above the planet’s surface, where temperatures reached around -175C. Arnaud Mahieux of the Belgian Institute for Space Aeronomy, who led the institute, explained the discovery, saying, “Since the temperature at some heights dips below the freezing temperature of carbon dioxide, we suspect that carbon dioxide ice might form there.”
The cold layer was found to be sandwiched between two warm layers, Dr. Mahieux said, adding, “The temperature profiles on the hot dayside and cool night side at altitudes above 120 km are extremely different, so at the terminator we are in a regime of transition with effects coming from both sides. The night side may be playing a greater role at one given altitude and the dayside might be playing a larger role at other altitudes,” but the researchers were keen to add that it is not yet confirmed whether this cold layer and the ice within is actually CO2, as at higher altitudes, oxygen, nitrogen and carbon monoxide are more prevalent.