Mars hasn’t always looked like it does today. Some 3 to 3.5 billion years ago, the planet underwent a huge tilt of 20 to 25 degrees. The gigantic Tharsis volcanic dome, which started to form over 3.7 billion years ago, grew so massive that it caused Mars’ crust and mantle to swivel around, shifting the Tharsis dome to the planet’s equator.
Mars’ gullies may be formed by dry ice processes rather than flowing liquid water, as previously thought. This is the conclusion of a study conducted by two French scientists published in Nature Geoscience. They show that, during Martian late winter and spring, underneath the seasonal CO2 ice layer heated by the Sun, intense gas fluxes can induce gas-lubricated debris flows which look like water-sculpted gullies on Earth.