Des fleurs sur Europe ?

Could flowers bloom on icy moon Europa?

* 18:02 05 May 2009 by Rachel Courtland, Cambridge
* For similar stories, visit the Solar System and Astrobiology Topic Guides

Physicist and futurist Freeman Dyson says we should search for extraterrestrial life where it is easiest to find, even if the conditions there are not ideal for life as we know it. Specifically, he says spacecraft should look for flowers – similar to those found in Earth's Arctic regions – on icy moons and comets in the outer solar system.

"I would say the strategy in looking for life in the universe [should be] to look for what's detectable, not what's probable," he said on Saturday at a conference in Cambridge, Massachusetts.

"We have a tendency among the theorists in this field to guess what's probable. In fact our guesses are likely to be wrong," Dyson said. "We never had as much imagination as nature."

He said spacecraft should hunt for signs of life on Jupiter's ice-covered moon Europa, since it would be detectable there.
Cracks in the ice

Europa, which is thought to have an ocean of liquid water beneath its icy shell, has long been a target for astrobiologists, who suspect the interior could be salubrious for life.

But digging deep into the moon's icy shell could be difficult. Estimates of the thickness of the ice have ranged between less than a kilometre to more than 100 km.

Life could be visible from orbiting spacecraft, however, if it made a home in cracks in Europa's shell that connect the surface to the interior, Dyson said.
Parabolic flowers

Such life might take the form of flowers with a parabolic shape that focuses the dim sunlight falling on Europa on the interior of the plant. Flowers with such shapes (pictured) are found in Arctic climes on Earth, where the plants have evolved to maximise solar energy.

Europa flowers could be detectable through a phenomenon called retroreflection, in which light gets reflected back to its source, Dyson said.

This optical effect is seen in light reflected from animals' eyes, and was used in the design of road signs and mirrors left behind on the moon by Apollo astronauts.
Orbiter missions

Although Dyson's 'sunflowers' may get their start on Europa, they could conceivably spread elsewhere in the solar system. "You can imagine once you have flowers that get nourished from below, they could evolve in the direction of being independent," Dyson said.

If plants spread to smaller, more distant objects in the solar system's two cometary reservoirs, the Kuiper belt and the Oort cloud, they would be less subject to gravity and could easily grow in size to maximise solar collection, Dyson said.

Europa will be one of two moons explored in depth by a planned collaboration between NASA and the European Space Agency beginning in 2026, when a pair of orbiters are set to reach Jupiter.

lambda0 a écrit:...Enfin, il peut très bien quand même trainer quelques graines sur Europe, et un peu partout dans le système solaire, même si ça ne risque pas germer : certains impacts d'astéroides sur Terre ont pu expédier dans l'espace des millions de tonnes de matériaux...