Lichen survives harsh Mars environment

Lichen exposed to harsh Mars-like conditions in a laboratory have been found to survive, preferring to cling to cracks in rocks and in gaps in the simulated Martian soil. The lichen collected from Antarctica were placed inside the German Aerospace Center’s Mars Simulation Laboratory for 34 days.

Surviving lichen in the German experiment. Credit: German Aerospace Center (DLR)

There they were subjected to the same atmospheric, temperature, radiation and pressure conditions they would experience if they were on the Martian surface.

“They adapted to the artificial martian environment and demonstrated the same activity that they would in their natural environment,” research scientist Jean-Pierre Paul de Vera told the European Geosciences Union (EGU) Meeting in Vienna today.

The lichen were most successful at surviving in small cracks in rocks and gaps in the simulated Martian soil, where they were offered some protection from the harsh radiation environment.

Billions of years ago, Mars was warmer and wetter and so much more favourable for life as we know it to exist. “If life arose on Mars four billion years ago, it could have remained to the present day in these niches,” said de Vera.

He warned that the results presented a serious challenge for future missions to Mars. “We must be extremely careful not to transport any terrestrial life forms to Mars that might contaminate the planet,” he said.

Elsewhere in the Solar System there is potential for life on moons around the two largest gas planets Jupiter and Saturn, the conference was told.

Jupiter’s icy moon Europa may host life within its deep ocean, which is kept warm by being constantly massaged by the gravitational pull of the giant planet. Lakes of liquid water are thought to exist just a few kilometres below the surface, embedded within the icy crust. They are likely connected to the surface through a rapid recycling process that can exchange material between the surface and ocean, suggesting that the distant moon may still be active today.

Neighbouring moons Callisto and Ganymede may also be hiding oceans below their rocky crust. A mission proposed by ESA, called JUICE (short for JUpiter ICy moon Explorer), could evaluate the potential of these worlds for hosting life. The fate of the JUICE mission, which is competing against two other missions, will be decided next week.

Around Saturn, Titan, with its thick atmosphere and surface seas of liquid methane and ethane, is a hot favourite for life. A new model discussed at EGU today speculates that late in Titan’s history the moon’s rocky core heated up sufficiently to release water, melting portions of an internal layer of ice.

“The bursting forth of hot water from the deep interior might eventually affect the crust of Titan at the top of the ocean, leading to the release of methane seen in the air, clouds, seas and lakes of Titan,” said Jonathan Lunine from Cornell University.

Lunine described a new mission proposed by NASA, the Titan Mare Explorer (TiME), which will land in one of Titan’s seas – the first time a ship will sail on an alien sea. Like ESA’s JUICE, however, TiME is also competing against two other NASA missions and will learn its fate later this year.

Coupled with Saturn’s moon Enceladus and its water-rich plumes bursting into space, the argument for life elsewhere in the Solar System – particularly on icy worlds in the outer Solar System – is compelling.

Related: Life could have survived in vents on Mars

Related: Did life on Earth begin on Mars?

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