NASA's Mars Reconnaissance Orbiter has returned data back to NASA suggesting that the current gullies on Mars were not formed due to liquid flowing water. Gullies look like former streams with debris and no water; Earth has gullies too that are replete with H2O, but Mars' physical features appear to have been created differently than Earth's landforms.


Image Source: By NikoLang (Own work (Screenshot)) [GPL (], via Wikimedia Commons