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JET PROPULSION LABORATORY
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Contact: Diane Ainsworth
FOR IMMEDIATE RELEASE
July 22, 1999
SUN NEVER SETS, FOR LONG, ON FAST-SPINNING, WATER-RICH ASTEROID
Spinning faster than any object ever observed in the solar
system, a lumpy, water-rich sphere known as 1998 KY26, about the
diameter of a baseball diamond, is rotating so swiftly that its
day ends almost as soon as it begins, NASA scientists report.
Asteroid 1998 KY26, where the Sun rises or sets every five
minutes, was observed June 2-8, 1998, shortly after it was
discovered and as it passed 800,000 kilometers (half a million
miles) from Earth, or about twice the distance between Earth and
the moon. Publishing their findings in tomorrow's issue of
Science magazine, Dr. Steven J. Ostro of NASA’s Jet Propulsion
Laboratory, Pasadena, CA, and an international team of
astronomers used a radar telescope in California and optical
telescopes in the Czech Republic, Hawaii, Arizona and California
to image the 30-meter (100-foot), water-rich ball as it twirled
through space. It is the smallest solar system object ever
studied in detail.
"These observations are a breakthrough for asteroid science
and a milestone in our exploration of the small bodies of the
solar system," Ostro said. "Enormous numbers of objects this
small are thought to exist very close to Earth, but this is the
first time we've been able to study one in detail. Ironically,
this asteroid is smaller than the radar instruments we used to
The asteroid's rotation period was calculated at just 10.7
minutes, compared to 24 hours for Earth and at least several
hours for the approximately 1,000 asteroids measured to date. In
addition to these findings, the minerals in 1998 KY26 probably
contain about a million gallons of water, enough to fill two or
three olympic-sized swimming pools, Ostro said.
"This asteroid is quite literally an oasis for future space
explorers," he said. "Its optical and radar properties suggest a
composition like carbonaceous chondrite meteorites, which contain
complex organic compounds that have been shown to have nutrient
value. These could be used as soil to grow food for future human
outposts. And among the 25,000 or so asteroids with very
reliably known orbits, 1998 KY26 is in an orbit that makes it the
most accessible to a spacecraft."
The solar system is thought to contain about 10 million
asteroids this small in orbits that cross Earth's, and about 1
billion in the main asteroid belt between Mars and Jupiter.
However, only a few dozen of these tiny asteroids have ever been
found and, until now, hardly anything was known about the nature
of these objects.
Ostro and his colleagues used the 70-meter-diameter (230-
foot) Goldstone, CA, antenna of NASA's Deep Space Network to
transmit radar signals continuously to the asteroid and turned a
34-meter-diameter (112-foot) antenna on it to collect echoes
bouncing back from the object.
1998 KY26's color and radar reflectivity showed similarities
to carbonaceous chondrites, primordial meteorites which formed
during the origin of the solar system, and unlike any rocks
formed on Earth. They contain complex organic compounds as well
as 10 percent to 20 percent water. Some carbonaceous chondrites
contain amino acids and nucleic acids, which are the building
blocks of proteins and DNA, and hence, are of interest to
scientists trying to unravel the origins of life.
A second team of astronomers used optical telescopes to
track 1998 KY26, which was discovered by the University of
Arizona's Spacewatch telescope, the world's first instrument
dedicated to searching for near-Earth asteroids. Dr. Petr Pravec
of the Czech Republic's Academy of Sciences said collisions
likely gave 1998 KY26 its rapid spin.
But one way or another, Pravec said, this object's 10.7-
minute "day" is the shortest of any known object in the solar
system. "The motion of the sky would be 135 times faster than it
is on Earth," he said. "Sunrises and sunsets take about two
minutes on Earth, but on 1998 KY26, they would take less than one
second. You'd see a sunrise or sunset every five minutes."
Dr. Scott Hudson of Washington State University in Pullman
found the asteroid's shape particularly surprising. Asteroids
thousands of times larger have spherical shapes as a result of
their large masses and strong gravitational fields, he said. 1998
KY26 is very unusual, however, because gravity and mass play no
significant role in its shape. Instead, the spheroid shape is the
result of collisions with other asteroids.
While much larger near-Earth asteroids could pose a long-
term collision hazard, 1998 KY26's size makes it harmless if it
were on a collision course. The asteroid would most likely
explode in the upper atmosphere and its fragments would fall
harmlessly to Earth. Moreover, 1998 KY26 is in an orbit whose
shape and low inclination with respect to the ecliptic plane make
it unusually easy to intercept.
Tracking of 1998 KY26 by Ostro and his colleagues in the
international scientific community was supported by NASA's Office
of Space Science, Washington, DC, and by the Czech Republic's
Academy of Sciences in Prague. JPL is a division of the
California Institute of Technology, Pasadena, CA.