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NASA's moon-smashing mission may have been doomed from the start |
Reports indicate that the NASA's LCROSS moon-smashing mission might have been doomed from
the beginning, as some scientists involved with the mission were predicting very
little, if anything, would be seen from the impact, despite a well publicized
observing campaign. According to a report in New Scientist, LCROSS ended today
morning when a two-tonne Centaur rocket hit the floor of a perpetually shadowed
crater near the lunar south pole, in an attempt to extract water. Scientists hoped
that dust and vapour kicked up by the impact would climb high enough to catch
sunlight, allowing a satellite that trailed behind the rocket to hunt for traces
of lunar water in the ejected debris. The Hubble Space Telescope and many Earth-based
observers were recruited to watch for a plume of debris rising from the impact
site. But while scientists voiced disappointment when no obvious plume was spotted
from any vantage point, some were not surprised. "We had a meeting in August where
we reported what we thought would be the scenario," said LCROSS team member Peter
Schultz of Brown University. He said that the new estimate for the mass that would
be lofted to a visible elevation was 100 to 1000 times lower than estimates that
had originally informed the mission. Schultz and his team derived their numbers
from projectile experiments using a high-speed vertical gun at NASA. Their results
differed strikingly from models that assumed debris would fly outward from the
impact site a 45 degrees angle. Instead, the team found that the fastest debris,
ejected at the initial stages of crater formation, tended to depart at an angle
closer to 30 degrees more of a sideways spray than an upward trajectory. Another
potential problem is that the 10 metre-long rocket was expected to produce a crater
only 20 to 30 m in diameter. That crater size is small enough for the shape and
orientation of the rocket to have played a role in how the debris was ejected,
confounding expectations. "Under those circumstances, the usual scaling relations
may not have applied as well as we thought, even though we tried to take that
into account," said LCROSS team member Don Korycansky of the University of California,
Santa Cruz. According to Paul Spudis of the Lunar and Planetary Institute in Houston,
Texas, a positive detection of water would not provide any information about the
extent and distribution of ice on the moon's surface, which is the point of looking
in the first place. "That tells me the fundamental rationale behind the mission
was flawed," he said. |
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