It is pointed out in the passage that Clementine and Lunar Prospector ----.

The entire future of human space exploration rests
on a patch of lunar ice. For the past two years NASA
has focused on designing a new crew vehicle and
launch system that could return astronauts to the
moon by 2018. The agency's ultimate goal is to
establish a permanent lunar base and use it for a
human mission to Mars. But the grand plan depends
on a risky prediction that NASA will find water ice in a
permanently shadowed crater basin at one of the
moon's poles. Plentiful ice deposits would be an
asset for lunar colonists, who could use the water for
life support or convert it to hydrogen and oxygen
rocket fuel. And two orbiters sent to the moon in the
1990s, Clementine and Lunar Prospector, found
evidence of ice in perpetually shadowed polar areas
where consistently frigid temperatures would
preserve the water carried to the moon by comet and
meteorite impacts. But some scientists have disputed
Clementine's radar data, and the anomalous neutron
emissions observed by Lunar Prospector could have
been caused by atomic hydrogen in the lunar soil
instead of ice.