The Galileo space probe, which has been orbiting Jupiter for nearly three years, has sent back the strongest evidence yet that salt-water oceans exist on Europa and Callisto. Finding deep oceans is vital in the search for lifeforms as organisms could not evolve without the benefit of liquid water.
Scientists have already gathered indirect geological evidence that Europa has an icy ocean, which is liquid beneath its frozen surface.
Now researchers from the American National Aeronautics and Space Administration (Nasa) and the University of California, Los Angeles (UCLA) have analysed disturbances of Jupiter's magnetic fields created by Europa and Callisto, indicating that the moons have subsurface oceans.
The moons do not have magnetic fields of their own so finding that they can disturb Jupiter's magnetic field suggests they must be able to have fields induced in them as a result of deep "conducting layers" under their surface - in other words oceans of salty water.
Oceans would raise the prospect of life being able to evolve near any hot thermal vents emerging from their floors. Nasa has already identified Europa as a possible site of life and is planning to send a probe there.Reuse content