One study, published in the recent edition of Nature, shows regions of Mars' ancient highlands held clay minerals that can form only when water is present, NASA said Wednesday in a news release

Lava buried clay-rich regions, but impact craters exposed the regions scattered across Mars, NASA said. The data for the study is from images taken by the Compact Reconnaissance Imaging Spectrometer for Mars and other instruments on the Mars Reconnaissance Orbiter, managed by NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"The big surprise from these new results is how pervasive and long-lasting Mars' water was, and how diverse the wet environments were," said Scott Murchie, CRISM principal investigator at Johns Hopkins University Applied Physics Laboratory.

The minerals, called phyllosilicates, recorded water's interaction with rocks dating back approximately 4.6 billion to 3.8 billion years ago, Murchie said.

"This is really exciting because we're finding dozens of sites where future missions can land to understand if Mars was ever habitable and if so, to look for signs of past life," said John Mustard, a CRISM member from Brown University and lead author of the Nature study.