Using images provided by the Mars Reconnaissance Orbiter (MRO), researchers at the California Institute of Technology detected salt signatures on the surface of the Red Planet, which is 2-2.3 billion years old.
This is the first mineral-based evidence of water on Mars and it challenges previous studies, which suggest there was liquid water on the planet 3-3.5 billion years ago.
Lead researcher Ellen K. Leask and Caltech professor Bethany L. Ehlmann mapped chloride salts left on the barren planet's surface after water that existed on Mars evaporated for an unknown reason.
After studying images accumulated over the last 15 years, researchers have found chloride salt deposits across the southern highlands, a heavily channelled part of the Martian surface, which constitutes two-thirds of the planet. They have also found salt signatures on top of the younger volcanic region.
"Chloride salt deposits on Mars are intriguing because they dissolve very readily and thus record the last stage of liquid water present at Mars' surface," the research paper published in the journal AGU Advance states.
The two researchers have also listed reasons to support their claim that these chloride salt deposits came from surface runoff rather than an underwater source.
Caltech researchers said these salt signatures are often found in small depressions, including perched above much deeper craters where no chloride is observed.
"These craters were one key to dating the salts: The fewer craters a terrain has, the younger it is. By counting the number of craters on an area of the surface, scientists can estimate its age," NASA has said in a statement.
Researchers "unexpectedly found spectral signatures for water ice" in several images associated with chlorides in the search for hydrated minerals.
"While the current climate of Mars is too cold/low pressure for liquid water to occur seasonally today, seasonal deposits in the past may have been able to melt, providing a possible source of localised, small volumes of water across the southern hemisphere of Mars," they write in the finding published in AGU Advances, a cross-disciplinary, open-access journal.
This new finding has fuelled curiosity among scientists involved in searching for the possibility of life on Mars and the timeline of microbial l if there ever was one.
The Caltech researchers' study coincides with a discovery based on powered rock samples collected from Mars surface by NASA's Curiosity Mars rover. NASA scientists said that several rock samples are "rich in a type of carbon that on Earth is associated with biological processes."
"On Earth, processes that would produce the carbon signal we're detecting on Mars are biological," Christopher House, a scientist at Penn State who led the study of Curiosity's findings, said.
"We have to understand whether the same explanation works for Mars, or if there are other explanations, because Mars is very different," he added.