(News from Mars that isn’t Curiosity related!) New data from the Mars Reconnaissance Orbiter provides firm evidence of carbon dioxide snow falling on the south pole of Mars. The atmosphere of Mars is about 95% CO2 and it has long been known that in the winter time CO2 freezes directly out of the atmosphere onto the residual polar ice caps. But snow??
Paul Hayne of NASA JPL and collaborators have for the first time detected CO2 ice clouds that are thick enough to produce snow that would fall and accumulate on the surface. Using infrared observations from the Mars Climate Sounder on the Mars Reconnaissance Orbiter from the southern Martian winter of 2006-2007, the team studied a number of “cold spots”, which are regions of anomalously low infrared brightness temperatures. They found a large CO2 cloud about 500 km in diameter that persisted over the south polar cap throughout the winter, as well as a number of smaller, shorter-lived CO2 ice clouds at latitudes between 70 and 80 degrees. The Mars Climate Sounder measures optical and infrared radiation from directly overhead as well as “sideways” (by looking towards the Martian horizon from orbit) to provide information about the temperature, pressure, particles and gases in the atmosphere.
The authors argue that the CO2 ice particles in the clouds are large enough to fall to the ground as snow over the lifetime of the cloud. The sideways views of the clouds also show that the CO2 ice particles extend all the way to the surface. These new results suggest that snowfall at the south pole likely builds up the extended winter polar ice cap.
For more details, see
- NASA Observations Point to ‘Dry Ice’ Snowfall on Mars, MRO news
- Carbon dioxide snow clouds on Mars: South polar winter observations by the Mars Climate Sounder, Hayne et al. (2012), Journal of Geophysical Research, 117, E08014, 23