The red tinge of Europa, one of Jupiter’s moons, could be caused by frozen
bits of bacteria. Their presence would also help explain Europa’s mysterious
infrared signal. Europa is mostly frozen water, but it absorbs infrared
radiation differently to how normal ice does. Researchers think this is
because something is binding the water molecules together. Salts of
magnesium sulphate frozen within the ice, for example, would make the
molecules vibrate at different frequencies. But no one has managed to come
up with the perfect mix of salts to explain all of Europa’s spectrum.
Astrogeophysicist Brad Dalton wondered if something else was bound up with
the water molecules. “Just on a lark, I asked a colleague of mine at
Yellowstone if he had any IR spectra of extremophile bacteria,” he says, and
he was shocked by how well they matched Europa’s mysterious spectrum. Then
he analysed three kinds of bacteria under the same sort of conditions as
Europa: its temperature is about -170 °C and at 0.01 millibars it has
virtually no atmosphere.
Preliminary results show that all three species, the ordinary gut bacteria
Escherichia coli, and extremophiles Deinococcus radiodurans and Sulfolobus
shibatae, are just as good at explaining Europa’s IR spectrum as the salts.
However Dalton says the two species that thrive under extreme conditions are
obviously more likely candidates for life on the icy moon. They also happen
to be pink and brown, which would help explain the red patches on the moon’s
face.
Bacteria couldn’t survive on Europa’s surface, but there might be liquid
water inside Europa’s icy crust capable of supporting life. “They could be
blasted out to the surface in some kind of eruption and flash frozen,” says
Dalton. He plans to present his results at the Lunar and Planetary Science
conference next spring.
Glenn Teeter from the Pacific Northwest National Laboratory in Washington
state says bacteria aren’t the simplest explanation for Europa’s spectrum.
“It does strike me as a bit far fetched,” he says. But it can’t be ruled out
until we go there to see.
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Author: Nicola Jones
New Scientist issue: 8th December 2001
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