Boost for life on Jupiter moon

Jupiter and some of its 16 or more moons

By Helen Briggs BBC News Online science reporter

The chances of finding life on other worlds have received a boost.

Data from the Galileo space probe's journey to Jupiter suggests an ocean on its moon, Europa, is somewhat Earth-like.

Scientists in the United States think the moon's icy crust is relatively thin.

There seem to be cracks and vents, which would allow gases, heat and organic matter to reach what may be water beneath.

It is informed speculation which suggests that the condition and environment will be suitable for life

Dr Mark Burchell, University of Kent

Dr Richard Greenberg and colleagues at the University of Arizona, Tucson, US, came to this conclusion after looking at images of the moon's cracked surface.

They were captured by the space probe Galileo, which has been flying past some of Jupiter's many moons over the past few years.

Dr Greenberg's team thinks the Europan sea has parallels with some of Earth's icy oceans. Surprisingly, perhaps, it appears to be more like the Arctic Ocean than Lake Vostok.

Buried bugs

Lake Vostok in Antarctica is one of the deepest-known bodies of fresh water on the planet.

At least 30 million years old, it is a model for some of the ice-covered oceans elsewhere in the Solar System.

Some have proposed that the lake might contain previously undiscovered lifeforms.

Lake Vostok has long fascinated scientists

But Vostok is now thought to be too isolated from surface influences to harbour anything more than the most primitive organisms.

Europa, though, appears more like the Arctic Ocean, the Earth's smallest ocean, which occupies the region around the North Pole.

The Arctic Ocean is exposed to air and heat by the cracking and melting of ice.

Europa too seems to have surface-to-ocean connections via cracks, thermal vents, and tidal displacement, according to the Arizona team.

Dr Cynan Ellis-Evans, of the British Antarctic Survey, is quick to see the significance.

"In thermodynamic terms life abhors equilibrium," he says. "These new interpretations suggest that a Europan ocean and its ice cap could be dynamically interacting with the moon's surface atmosphere over short time scales that increase opportunities for life to exist and evolve."

Seeds of life

One intriguing possibility is that sulphur ejected from Jupiter's volcanic moon, Io, could make it across to Europa.

"If we're getting a sulphur source going into the lake it's an exciting possibility," Dr Ellis-Evans adds. "It increases the opportunity for life".

Europa

The only body, other than the Earth, that may contain large quantities of liquid water

The most likely candidate in the Solar System for containing alien life

The lack of impact craters suggests its surface is very young

Astrobiologists had thought the ice sheet covering the moon was too thick to allow anything to get in. The new research will give them food for thought.

"It is informed speculation which suggests that the condition and environment will be suitable for life," says Dr Mark Burchell, a space scientist at the University of Kent in Canterbury, UK.

One scenario is that a meteoroid crashing into Europa could have punched through the ice, carrying the building blocks of life.

"Dust and meteorites carrying organic or volatile materials could have been delivered to the ocean below the surface," he says.

The American space agency is seriously considering sending a robotic probe to Europa to drill through the ice.

The research, published in the US journal Reviews of Geophysics, will be welcome news for the scientists lobbying Nasa to go.