What creates these long and nearly straight grooves on Mars?
linear gullies, they appear on the sides of some sandy slopes during Martian spring, have nearly constant width, extend for as long as two kilometers, and have raised banks along their sides.
Unlike most water flows, they do not appear to have areas of dried debris at the downhill end.
A leading hypothesis -- actually
being tested here on Earth -- is that these linear gullies are caused by chunks of carbon dioxide ice
breaking off and sliding down hills while
sublimating into gas, eventually completely evaporating into thin air.
If true, these natural
dry-ice sleds may well provide
future adventurers a smooth ride on cushions of escaping carbon dioxide.
The above recently-released image was taken in 2006 by the
HiRISE camera on board the
Mars Reconnaissance Orbiter currently orbiting Mars.
LPL (U. Arizona),