NASA scientists have finally seen in their data a debris plume created
by the impact of a moon probe last week.
The faint plume was seen in the data from the engineered
crash one week after the impact
of the LCROSS probe.
Scientists are hoping that analysis of the plume will show
signs of water ice ejected from the probe's
target crater, named Cabeus, at the lunar south pole.
The debris plume, created by the probe's Centaur stage
rocket, was captured by the LCROSS ultraviolet/visible and near infra-red
spectrometer. Its signature was faint, but distinct.
"There is a clear indication of a plume of vapor and
fine debris," said Anthony Colaprete, LCROSS principal investigator and
project scientist.
The magnitude, form, and visibility of the debris plume add
additional information about the concentrations and state of the material at
the impact site.
"Within the range of model predictions we made, the ejecta
brightness appears to be at the low end of our predictions and this may be a
clue to the properties of the material the Centaur impacted," Colaprete
said.
The LCROSS spacecraft also captured the Centaur impact flash
in both mid-infrared (MIR) thermal cameras over a couple of seconds. The
temperature of the flash provides valuable information about the composition of
the material at the impact site.
LCROSS also captured emissions and absorption spectra across
the flash using an ultraviolet/visible spectrometer. Different materials
release or absorb energy at specific wavelengths that are measurable by the
spectrometers.
With the spacecraft returning data until virtually the last
second, the thermal and near-infrared cameras captured excellent images of the
Centaur impact crater at a resolution of less than 6.5 feet (2 m). The images
indicate that the crater was about 92 feet (28 m) wide.
"The images of the floor of Cabeus are exciting,"
Colaprete said. "Being able to image the Centaur crater helps us
reconstruct the impact process, which in turn helps us understand the
observations of the flash and ejecta plume."
The LCROSS team will continue combing through and examining
the probe's data in the coming weeks to see if they can find signs of water ice.
"We are blown away by the data returned,"
Colaprete said. "The team is working hard on the analysis and the data
appear to be of very high quality."
Water has already
been detected in small quantities all over the lunar surface, bound to the
particles of dirt that coat the moon.
And evidence from other spacecraft suggests there is water ice in permanently shadowed craters like Cabeus.
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