American scientists claim to have found evidence that suggests Mars had a warm and wet climate which could have supported life some 3.5 billion years ago.

A team, led by planetary geologists at Brown University, found mounds of a mineral deposited on a volcanic cone less than 3.5 billion years ago that speak of a warm and wet past, and may preserve evidence of one of the most recent habitable microenvironments on the red planet.

Observations by the National Aeronautics and Space Administration‘s Mars Reconnaissance Orbiter enabled the researchers to identify the mineral as hydrated silica which can be dissolved, transported and concentrated by hot water or steam – a dead ringer that water was present at some time.

The mineral and the mounds’ location on the flanks of a volcanic cone provide the best evidence yet on Mars for an intact deposit from a hydrothermal environment — a steam fumarole or a hot spring, said the researchers.

Such environments might have provided habitats for some of Earth’s earliest life forms, they hoped.

“The heat and water required to create this deposit probably made this a habitable zone,” said J. R. Skok, lead author of the study, published in journal Nature Geoscience. “If life did exist there, this would be a promising spot where it would have been entombed – a microbial mortuary, so to speak.”

No studies have determined whether Mars has ever supported life, but this finding adds to accumulating evidence that at some times and in some places, Mars hosted favourable climate for microbial life.

The deposit is located in the sprawling, flat, volcanic zone known as Syrtis Major and was believed to have been left during the early Hesperian period, when most of Mars was already turning chilly and arid.

“Mars is just drying out,” Skok said, “and this is one last hospitable spot in a cooling, drying Mars.”

Concentrations of hydrated silica have been identified on Mars previously, including a nearly pure patch found by NASA’s Mars Exploration Rover Spirit in 2007. However, this is the first found in an intact setting that clearly signals the mineral’s origin.

“You have spectacular context for this deposit,” Skok said. “It’s right on the flank of a volcano. The setting remains essentially the same as it was when the silica was deposited.”

Observations by cameras on the Mars Reconnaissance Orbiter revealed patches of bright deposits near the summit of the cone, fanning down its flank, and on flatter ground in the vicinity.

The Brown researchers partnered with Scott Murchie, of Johns Hopkins University Applied Physics Laboratory, to analyse the bright exposures with the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the orbiter.

Hydrated silica identified by the spectrometer in uphill locations, confirmed by stereo imaging, indicates that hot springs or fumaroles fed by underground heating created these deposits. Silica deposits around hydrothermal vents in Iceland are among the best parallels on Earth.

“The habitable zone would have been within and alongside the conduits carrying the heated water,” Murchie said.

The surface of the moon contains not just water, but a rich mix of elements, including silver and carbon dioxide, astronomers said.

The findings to be published in the journal Science come from an analysis of data from the Lunar Crater Observation and Sensing Satellite (LCROSS) experiment that crashed into the moon last year.

Data from the experiment had already shown water is even more abundant on the moon’s craters than expected.

Scientists said that they had found light hydrocarbons, traces of sulphur and carbon dioxide in the plume of dust kicked up by the crashing craft. They have also been able to estimate more thoroughly the amount of water in the crater, which they believe makes up about 5.6 per cent of the mass in the crater. There’s enough water in the form of pure ice crystals to be useful for humans, both as pure water or separated into parts for fuel, the scientists found. Silver was found in trace amounts among the light metals that also included sodium and mercury.

The dramatic experiment in 2009 crashed the LCROSS spacecraft into the moon’s Cabeus crater, sending a huge plume of dust 10 kilometres upward to gather data about ice that was suspected to be hidden in the perpetually dark lunar craters. The components of the dust were analysed by another space craft called Lunar Reconnaissance Orbiter (LRO) that followed closely behind, gathering data.

Major telescopes around the world were also aimed at the Cabeus crater on the moon’s south pole to capture data from the dust plume. The analysis shows how rich the moon is in useful minerals and that it remains chemically active and has a water cycle, NASA scientists said.

“Seeing mostly pure water ice grains in the plume means water ice was somehow delivered to the moon in the past, or chemical processes have been causing ice to accumulate in large quantities,” said Anthony Colaprete, LCROSS project scientist and principal investigator at NASA’s Ames Research Centre in California.

“Also, the diversity and abundance of certain materials called volatiles in the plume suggest a variety of sources, like comets and asteroids, and an active water cycle within the lunar shadows.” The rocket’s impact was designed to replicate that of the large, natural asteroids that slam into the moon several times a month.

The NASA probe targeted a 100-kilometre wide, four-kilometre deep crater and was timed to strike when lighting conditions are ideal for observing the impact. The 585-kg craft created an impact crater about two metres deep.