[meteorite-list] New Impact Site Selected for LCROSS

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 29 Sep 2009 12:37:34 -0700 (PDT)
Message-ID: <200909291937.n8TJbYfi028891_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/lcross/090928crater/

New impact site for LCROSS water-hunting mission
BY STEPHEN CLARK
SPACEFLIGHT NOW
September 28, 2009

Officials have shifted the target for next week's smash into the moon by
the LCROSS lunar impactor mission after a new analysis showed another
crater has a better chance of yielding results verifying the existence
of water at the south pole.

NASA announced on Sept. 11 the probe would be targeting a crater named
Cabeus A near the moon's south pole. In an update posted to the LCROSS
Web site Monday, the agency said scientists agreed to select a new
crater based on the latest data from current and retired lunar orbiters.

The impact is scheduled to occur around 1130 GMT (7:30 a.m. EDT) on Oct. 9.

The new crater, called Cabeus, was on the short list of candidate
targets considered by the science team before officials made their
initial decision earlier this month.

"The LCROSS team concluded that Cabeus provided the best chance for
meeting its mission goals," the statement said.

Cabeus is not far from Cabeus A near the moon's south pole. Both craters
have floors that never receive light due to the low sun angles at the
polar regions.

Scientists made the change based on the latest understanding of hydrogen
concentrations in the region from information recently collected by the
Lunar Reconnaissance Orbiter and archived data from the Lunar Prospector
mission more than 10 years ago.

"The general consensus of lunar experts led by the LCROSS science team
is that Cabeus shows, with the greatest level of certainty, the highest
hydrogen concentrations at the south pole," the Web update said.

New terrain models compiled from topographic information from LRO and
Japan's Kaguya spacecraft also show a small valley along the Cabeus
perimeter rim. The previously-unseen notch will allow sunlight to
illuminate material propelled above the surface by the high-speed impact
of the mission's Centaur rocket stage.

"While the ejecta does have to fly to higher elevations to be observed
by Earth assets, a shadow cast by a large hill along the Cabeus ridge,
provides an excellent, high-contrast, back drop for ejecta and vapor
measurements," the posting said.

The LCROSS shepherding spacecraft is towing the Centaur stage, part of
its Atlas 5 launch vehicle, through space and aligning its trajectory to
hit the moon next Friday.

Officials will continue to refine the exact point of impact over the
next few days to avoid rough spots and to maximize lighting conditions,
NASA said.

The probe will release the Centaur a few hours before impact and back
away from the inert rocket. A suite of instruments on the spacecraft,
along with telescopes on Earth, will observe the Centaur's explosive
collision and the resulting cloud of lunar debris sent skyward by the
event.

The spacecraft will fly through the lunar dust on the way to its own
impact, streaming live data back to Earth about the material's composition.

Scientists hope to confirm the debris contains water ice, a hypothesis
established from data showing hydrogen inside permanently shadowed
craters at the moon's poles.

NASA last week announced new results indicating lunar water is more
widespread than earlier thought, including detections of potential water
further away from the poles.

The $79 million LCROSS mission is designed to provide more answers in
the search.
Received on Tue 29 Sep 2009 03:37:34 PM PDT