Not so long ago, Venus was thought to be a lush Earth-like place thanks to its atmosphere and similar size to our planet. Hopes for a new outer-space Eden were dashed once the first man-made probes found that its atmosphere was mostly carbon dioxide and that temperatures on the Venusian surface can get up to around 425 degrees Celsius (797 degrees Fahrenheit). It's not exactly where you’d want to build your summer home.
But now, Venus has offered up another surprise. Turns out this hot planet has a bit of a cold streak.
The European Space Agency orbiter Venus Express has spotted a layer of atmosphere 77 miles above the Venusian surface that is a cool -175 degrees Celsius (-283 Fahrenheit).
“Since the temperature at some heights dips below the freezing temperature of carbon dioxide, we suspect that carbon dioxide ice might form there,” Belgian Institute for Space Aeronomy researcher Arnaud Mahieux said in a statement Monday.
Mahieux and several colleagues reported the find in the Journal of Geophysical Research.
The Venus cold streak may also be a bright streak; the researchers think that if carbon dioxide ice or snow is forming in the cold layer, it would be more reflective than other parts of the atmosphere. However, such reflections could also be caused by atmospheric disturbances, so researchers have to be cautious, according to Mahieux.
Future observations will also look at how other components of Venus’ atmosphere, including carbon monoxide, nitrogen and oxygen, interact with the cold layer and its surrounding regions.
But the finding “is special, as we do not see a similar temperature profile ... in the atmospheres of Earth or Mars, which have different chemical compositions and temperature conditions,” ESA scientist Hakan Svedhem said in a statement.
SOURCE: Mahieux et al. “Densities and temperatures in the Venus mesosphere and lower thermosphere retrieved from SOIR on board Venus Express. Carbon dioxide measurements at the Venus terminator,” Journal of Geophysical Research – Planets 117: E07001, 2012.