Tag Archives: dry ice

Evaporating dry ice chunks create gouges on Mars

Scientists think they have solved the mystery of the gouges that appear seasonally on some hillsides on Mars: Chunks of dry ice that slide down the slope and then evaporate, leaving no trace.

During the martian winter, carbon dioxide ice freezes over parts of the planet’s surface and sublimates back into a gas during the spring thaw. But according to the model presented here today at a meeting of the American Geophysical Union, chunks of warming dry ice may also break off from the crests of dunes and skid down slopes. This is no ordinary tumble—according to the model, the bases of the chunks are continually sublimating, resulting in a hovercraftlike motion that gouges the dune while propelling the ice down slopes. Solid ice that survives to the bottom settles into a pit before dissipating back into the atmosphere.

Dry ice evaporation creates the fresh gullies on Mars

New data from Mars Reconnaissance Orbiter shows that the fresh gullies that have been seen on the Red Planet are caused by dry ice evaporation, not liquid water as had been hoped.

Dundas and collaborators used the High Resolution Imaging Science Experiment (HiRISE) camera on MRO to examine gullies at 356 sites on Mars, beginning in 2006. Thirty-eight of the sites showed active gully formation, such as new channel segments and increased deposits at the downhill end of some gullies.

Using dated before-and-after images, researchers determined the timing of this activity coincided with seasonal carbon-dioxide frost and temperatures that would not have allowed for liquid water.

Frozen carbon dioxide, commonly called dry ice, does not exist naturally on Earth, but is plentiful on Mars. It has been linked to active processes on Mars such as carbon dioxide gas geysers and lines on sand dunes plowed by blocks of dry ice. One mechanism by which carbon-dioxide frost might drive gully flows is by gas that is sublimating from the frost providing lubrication for dry material to flow. Another may be slides due to the accumulating weight of seasonal frost buildup on steep slopes.

The findings in this latest report suggest all of the fresh-appearing gullies seen on Mars can be attributed to processes currently underway, whereas earlier hypotheses suggested they formed thousands to millions of years ago when climate conditions were possibly conducive to liquid water on Mars.