The chances that life exists on Jupiter's moon Europa look better than ever. The moon's icy crust may be just a few kilometres thick - perhaps thin enough to crack open under tidal stresses and allow life in the oceans below to flourish by absorbing the Sun's energy. Astrobiologists fear that if the crust is too thick, any possible life would be limited to organisms that use chemical energy from hydrothermal vents, a very restricted niche. Now a team from the University of Arizona's Lunar and Planetary Laboratory, led by Richard Greenberg, have been studying data from NASA's Galileo probe, which is in orbit around Jupiter. They have built up a strong case over the past few years that Europa's ice is less than 10 kilometres thick. And they outlined their most recent results in two talks at the conference last week, as well as in Reviews of Geophysics (vol 40, p 1).
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