Alien fossils: Evidence of ancient life on Mars could be trapped on slopes of volcano



Scientists have pinpointed a region on Mars where ancient lifeforms may be trapped under a layer of mineral deposits.

The climate on the red planet 3.5 billion years ago changed dramatically from a relatively warm, wet period to one that was arid and cold.

Now a team of scientists has discovered mounds of a mineral deposited on a volcanic cone less than 3.5 billion years ago that may preserve evidence of one of the most recent habitable microenvironments on Mars.

This volcanic cone in the Nili Patera caldera on Mars has hydrothermal mineral deposits on its southern slopes

Observations by NASA's Mars Reconnaissance Orbiter enabled researchers to identify the mineral as hydrated silica, a clear sign that water was present at some time. Silica deposits around hydrothermal vents in Iceland are among the best parallels on Earth.

The discovery of the mineral on the flanks of a volcanic cone provide the best evidence yet found on Mars for an intact deposit from a hydrothermal environment — a steam vent or a hot spring.



Silicate deposits have been discovered before but these new findings are in an area which would have been also very warm - a perfect environment for life.

'The heat and water required to create this deposit probably made this a habitable zone,' said J.R. Skok, a graduate student at Brown and lead author of the paper in 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 environments 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.'

A three-dimensional image of a trough in the Nili Fossae region of Mars shows purple colours which indicate the presence of silicates in the area

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.'



The small, degraded cone rises about 100 metres from the floor of a shallow bowl named Nili Patera. Before the cone formed, free-flowing lava blanketed nearby plains.

The collapse of an underground magma chamber from which lava had emanated created the bowl.

Subsequent flows of liquid coated the floor of Nili Patera. The cone grew from even later flows, apparently after evolution of the underground magma had thickened its texture so that the erupted lava would mound up.

A colour-enhanced image of the delta in Jezero Crater, which once held a lake, scientists believe

'We can read a series of chapters in this history book and know that the cone grew from the last gasp of a giant volcanic system,' said John Mustard, professor of geological sciences and a co-author of the paper.

'The cooling and solidification of most of the magma concentrated its silica and water content.'

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.

Silica can be dissolved, transported and concentrated by hot water or steam. Hydrated silica identified by the spectrometer in uphill locations indicates that hot springs or fumaroles fed by underground heating created these deposits.

