A NASA spacecraft
destined to crash into a moon crater in the hunt for hidden caches of water ice
has a new target, the space agency announced Monday.
The
decision means that NASA's LCROSS probe and its spent Centaur rocket stage will now crash
into the large crater Cabeus, and not the nearby (and smaller) Cabeus A crater previously
targeted, when they slam
into the moon on Oct. 9.
Scientists
pulled the lunar
switcheroo based on a continuing analysis of data from recent moon-watching
spacecraft. The data suggests the new target Cabeus has the highest
concentration of hydrogen - an indication of possible water ice - than anywhere
else at the lunar south pole.
"The LCROSS
team concluded that Cabeus provided the best chance for meeting its mission
goals," mission managers said in a statement.
The news
comes less than a week after scientists announced the discovery
of water on the moon in the form of water molecules bound to the lunar dirt.
Cabeus is a
large crater about 60 miles (98 km) in diameter that sits at 84.9 degrees
south, 35.5 degrees west at the moon's south pole. It has two nearby satellite
craters: the 25-mile (40-km) wide Cabeus A - LCROSS' original target - and Cabeus
B, which is about 38 miles (61 km) in diameter.
A small
valley etched into the otherwise tall crater ridge of Cabeus should allow sunlight
to shine on the ejecta cloud kicked up when LCROSS and its Centaur rocket stage
crash into the moon in successive impacts. The shadow of a large hill along the
ridge should provide enough contrast for Earth-based measurements of the plume's
composition, NASA officials added.
"During the
last days of the mission, the LCROSS team will continue to refine the exact
point of impact within Cabeus crater to avoid rough spots, and to maximize
solar illumination of the debris plume and Earth observations," NASA officials
said.
NASA's
LCROSS probe - officially known as the Lunar Crater Observation and Sensing Satellite
- is actually a pair of vehicles headed for what maybe one of the most watched
cosmic collisions in history.
The $79
million mission launched in June along with NASA's powerful Lunar
Reconnaissance Orbiter as part of the agency's first new missions to explore
the moon. Finding usable water ice on the moon would be a boon for future
manned missions to the lunar south pole since it could be used as a resource to
supply astronauts with drinking water, or split into oxygen and hydrogen to create
rocket fuel.
LCROSS and
its spent Centaur rocket stage have been making sweeping orbits around the
Earth as they fly ever-closer
to impact day. The Centaur stage will crash into the target first, with
LCROSS expected to fly through the resulting debris cloud before meeting its
own demise a few minutes later.
Data beamed
to Earth from LCROSS during the two impacts, as well as observations from a
flotilla of spacecraft and telescopes on Earth and in space, will be recorded
to determine whether the two vehicles kick up any water ice among the ejecta
from their successive crashes.
LCROSS
scientists have dedicated their mission to the memory of the late CBS anchorman
Walter Cronkite.
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