Officials at the European Space Agency (ESA) say that data relayed to Earth by the Venus Express orbiter point to the presence of an extremely-cold layer in the planet's upper atmosphere. Temperatures there may be low enough to allow for carbon dioxide (CO2) to freeze.
This means that precipitations could exist on our neighboring planet, either as snow or as ice. If future studies manage to confirm this hypothesis, then this would be one of the most amazing discoveries ever made at Venus, experts say.
The ESA Venus Express spacecraft was launched into space aboard a Russian-built Souyz-FG Fregat delivery system. The latter took off from the Baikonur Cosmodrome, in Kazakhstan, on November 9, 2005. Orbital insertion around the planet was achieved on April 11, 2006.
One of the things that researchers knew even before the mission started was that the neighboring world contained very large amounts of carbon dioxide in its atmosphere, and that its surface was very hot. The image scientists had did not make the planet look like a suitable candidate for finding life.
In the new study, which was based on 5 years of Venus Express data, researchers were able to identify a cold layer in the planet's atmosphere, at an altitude of around 125 kilometers (77.7 miles). Average temperatures at this altitude are around -175 degrees Celsius (-283ºF).
This means that the layer is about as cold as the surface of Titan, Saturn's largest moon, which is located several times farther away from the Sun than Venus. The atmospheric layer is also much colder than any environment on or above our planet.
By cross-referencing these data with atmospheric pressure values (for all altitudes) and CO2 concentrations, the research group, from the Belgian Institute for Space Aeronomy, was able to determine that carbon dioxide precipitations may form high in the Venusian atmosphere.
“Since the temperature at some heights dips below the freezing temperature of carbon dioxide, we suspect that carbon dioxide ice might form there,” explains BISA expert Arnaud Mahieux, who is also the lead author of the study.
A paper detailing the findings, entitled ““Densities and temperatures in the Venus mesosphere and lower thermosphere retrieved from SOIR on board Venus Express. Carbon dioxide measurements at the Venus terminator,” appears in the latest issue of the esteemed Journal of Geophysical Research.
“The finding is very new and we still need to think about and understand what the implications will be,” concludes ESA Venus Express project scientist, Håkan Svedhem.