Observations by NASA’s Mars Reconnaissance Orbiter have detected carbon-dioxide snow clouds on Mars and evidence of carbon-dioxide snow falling to the surface – the only evidence of dry-ice snowfall anywhere in our Solar System.
Using an infrared spectrometer a team lead by Paul Hayne took observations of clouds around the southern pole of Mars, looking at information about temperatures, particle sizes and their concentrations. They found a tall carbon dioxide cloud about 300 miles (500 kilometers) in diameter persisting over the pole and smaller, shorter-lived, lower-altitude carbon dioxide ice clouds at latitudes from 70 to 80 degrees south.
Crucially, the infrared spectrum signature existed in particles all the way to the Martian surface, indicating carbon dioxide snowfall. The precise mechanism is not known – whether the dry ice forms crystals and falls as snow in the way we would immediately recognise, or whether it hits the cold ground of the Mars southern pole and then crystallises as frost.
The study is being published in the Journal of Geophysical Research. The Lead Author is Paul Hayne.
This article summarised from materials provided by NASA.