Details of a proposed mission to Jupiter and its moons to search for hints of life have been announced by NASA scientists.
The Jupiter Icy Moons Orbiter (JIMO) will be the first spacecraft to be powered by a uranium nuclear reactor. NASA plans to launch the vessel after 2011 to sniff out life or its potential toeholds on Jupiter and three of its moons.
JIMO will also be the largest spacecraft ever sent to the outer Solar System, and the first in a series of nuclear-powered spacecraft that form "Project Prometheus," a programme NASA initiated earlier in 2003.
The huge probe will journey to Jupiter and its moons Callisto, Ganymede, and Europa - suspected of harbouring subsurface water oceans.
The three planet-sized moons are also among the largest of Jupiter's 61 satellites. Besides water, the icy moons show signs of containing key chemicals and energy sources. These qualities make them tantalising targets in the search for extraterrestrial life.
"We don't know if life is there. But this mission will allow us to ask that question with some pretty sound tools," NASA's Christopher McKay told the Associated Press.
Scientists outlined the priorities and goals of JIMO at a meeting of the American Geophysical Union in San Francisco, US on Monday.
"In order to even begin searching for life on these icy moons, we must answer the basic questions," says William Moore at the University of California and Nicholas Makris at the Massachusetts Institute of Technology.
"How thick is the ice? And how and where and when does the ocean communicate with the surface?" Radar, thermal imaging, and seismic sensors placed on the moons might answer these questions, they suggested during a commentary at the meeting.
Moore and Makris say Europa holds the most promise for life because it may have the most dynamic oceans due to the intense tug of Jupiter's gravity. The giant planet's gravity is so strong it deforms another moon, Io, to the extent that it boasts the most volcanic activity in the Solar System.
This destabilising force appears to make Europa's putative ocean more dynamic, suggests indirect evidence. Callisto and Ganymede's suspected oceans appear to be sandwiched more firmly between layers of ice.
"If Europa has an ocean, and if that ocean contains life, and if water from the ocean is carried up to the surface, then signs of life may be contained in organic material on the surface," suggest McKay and colleagues.
JIMO will be powered by a fission reactor that will split uranium atoms, releasing heat that can be converted into electricity. The fission reactor would deliver more than a hundred times more power than a non-nuclear source of similar size, according to NASA. Such power is crucial for propelling the spacecraft - which may be 30 metres long - a billion or more kilometres to Jupiter.
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18:00 07 October 2008
17:56 07 October 2008
