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Don Savage
Headquarters, Washington             February 20, 2003
(Phone: 202/358-1727)

DC Agle 
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  818/393-9011)

RELEASE: 03-077

NASA SOLVES HALF-CENTURY OLD MOON MYSTERY

     In the early morning hours of Nov. 15, 1953, an amateur 
astronomer in Oklahoma photographed what he believed to be a massive, 
white-hot fireball of vaporized rock rising from the center of the 
moon's face. If his theory was right, Dr. Leon Stuart would be the 
first and only human in history to witness and document the impact of 
an asteroid-sized body impacting the moon's scarred exterior.

Almost a half-century, numerous space probes and six manned lunar 
landings later, what had become known in astronomy circles, as 
"Stuart's Event" was still an unproven, controversial theory. Skeptics 
dismissed Stuart's data as inconclusive and claimed the flash was a 
result of a meteorite entering Earth's atmosphere. That is, until Dr.
Bonnie J. Buratti, a scientist at NASA's Jet Propulsion Laboratory 
(JPL) in Pasadena, and Lane Johnson of Pomona College, Claremont, 
Calif., took a fresh look at the 50-year- old lunar mystery.

"Stuart's remarkable photograph of the collision gave us an excellent 
starting point in our search," said Buratti. "We were able to estimate 
the energy produced by the collision. But we calculated that any 
crater resulting from the collision would have been too small to be 
seen by even the best Earth-based telescopes, so we looked elsewhere 
for proof."

Buratti and Lane's reconnaissance of the 35-kilometer (21.75- mile) 
wide region where the impact likely occurred led them to observations 
made by spacecraft orbiting the moon. First, they dusted off 
photographs taken from the Lunar Orbiter spacecraft back in 1967, but 
none of the craters appeared a likely candidate. Then they consulted 
the more detailed imagery taken from the Clementine spacecraft in 
1994.

"Using Stuart's photograph of the lunar flash, we estimated the object 
that hit the moon was approximately 20 meters (65.6 feet) across, and 
the resulting crater would be in the range of one to two kilometers 
(.62 to 1.24 miles) across. We were looking for fresh craters with a 
non-eroded appearance," Buratti said.

Part of what makes a moon crater look "fresh" is the appearance of a 
bluish tinge to the surface. This bluish tinge indicates lunar soil 
that is relatively untouched by a process called "space weathering," 
which reddens the soil. Another indicator of a fresh crater is that it 
reflects distinctly more light than the surrounding area.

Buratti and Lane's search of images from the Clementine mission 
revealed a 1.5-kilometer (0.93 mile) wide crater. It had a bright 
blue, fresh-appearing layer of material surrounding the impact site, 
and it was located in the middle of Stuart's photograph of the 1953 
flash. The crater's size is consistent with the energy produced by the 
observed flash; it has the right color and reflectance, and it is the 
right shape.

Having the vital statistics of Stuart's crater, Buratti and Lane 
calculated the energy released at impact was about .5 megatons (35 
times more powerful than the Hiroshima atomic bomb). They estimate 
such events occur on the lunar surface once every half-century.

"To me this is the celestial equivalent of observing a once-
in-a-century hurricane," observed Buratti. "We're taught the moon is 
geologically dead, but this proves that it is not. Here we can 
actually see weather on the moon," she said. 

While Dr. Stuart passed on in 1968, his son Jerry Stuart offered some 
thoughts about Buratti and Lane's findings. "Astronomy is all about 
investigation and discovery. It was my father's passion, and I know he 
would be quite pleased," he said.

Buratti and Lane's study appears in the latest issue of the space 
journal, Icarus. 

The NASA Planetary Geology and Planetary Astronomy Programs and the 
National Science Foundation funded Buratti's work. The California 
Institute of Technology manages JPL for NASA.

More information about NASA's planetary missions, astronomical 
observations, and laboratory measurements is available on the Internet 
at:

http://pds.jpl.nasa.gov

Information about NASA programs is available on the Internet at:

www.nasa.gov

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