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Thursday, 31 October, 2002, 12:54 GMT
Jupiter moon's 'elevator of life'
Europa, Nasa
Europa's icy crust may cover a life-filled ocean
If life does exist on Jupiter's moon Europa, evidence of it may be found near to the surface and within the grasp of visiting spacecraft, say scientists.

There is good evidence that Europa hides a liquid ocean many kilometres below its icy crust.

Scientists would like to one day explore this ocean for signs of life, but even if a lander could reach the moon, the practical problems of drilling through the vast ice sheet are immense.

But new research suggests this may not be necessary as there could be processes at work on the satellite that regularly bring deep-seated material to the surface.

Life on the elevator

Scientists at the University of Colorado at Boulder, US, have spotted phenomena on surface images of Europa taken by the Galileo probe on its flybys in the late 1990s.


Organisms might be carried on a slow ride from the bottom to the top of Europa's icy crust

Professor Robert Pappalardo, Colorado University
They believe that these mysterious pits among the cracks and ridges of the ice sheet could indicate where matter from the ocean below is churned upwards towards the surface.

If this is true, then evidence of organisms from the ocean might be found much closer to the surface than previously thought.

Professor Robert Pappalardo, who led the research, said that closer examination of these "elevators" - some of which are several kilometres in diameter - might reveal "dormant organisms" if they are present in the ocean.

'Like a lava lamp'

He said: "Organisms might be carried on a slow ride from the bottom to the top of Europa's icy crust.

"Sampling the surface composition may provide direct insights into the nature of the ocean deep below.

He added: "Europa acts like a planetary lava lamp, carrying material from near the surface down to the ocean, and, if they exist, potentially transporting organisms from the ocean up toward the surface.

"Just a mile or two beneath the surface, the conditions may be warm enough to allow organisms to survive the journey."

Finding food

Other research at the university is investigating the possibility that ice irradiation at the surface of Europa might create potential nutrients which could be carried downwards by warping and shifting of the ice.

Other research has suggested that holes punched through the crust by large space rocks could have refilled with water from the ocean beneath - again offering an opportunity for evidence of life to be transported closer to the surface.

These rocks might also be sources of the materials needed to construct life.

The reason why Europa's core is likely to be surrounded by a 26-km-deep ocean of water lies in the intense gravitational forces exerted on the satellite by Jupiter.

The giant planet pulls and stretches the moon through its 3.5-day oblong orbit, generating heat deep down that should be sufficient to keep any water in a liquid state.

The US space agency plans a Europa orbiter mission in 2010, which will hopefully confirm the presence of the ocean and spot promising sites for a landing.

See also:

26 Jun 98 | Science/Nature
10 Dec 99 | Science/Nature
01 Oct 02 | Science/Nature
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