In a risky flyby, NASA’s ailing Deep Space 1 spacecraft
successfully navigated past a comet, giving researchers the
best look ever inside the glowing core of icy dust and gas.
The space probe’s close encounter with comet Borrelly
provided the best-resolution pictures of the comet to date.
The already-successful Deep Space 1, without protection from
the little-known comet environment, whizzed by just 2,200
kilometers (1,400 miles) from the rocky, icy nucleus of the
10-kilometer-long (more than 6-mile-long) comet.
Exceeding the team’s expectations of how this elderly
spacecraft would perform, the intrepid spacefarer sent back
black-and-white photos of the inner core of the comet. It
also measured the types of gases and infrared waves around
the comet, and how the gases interacted with the solar wind.
“Deep Space 1 plunged into the heart of comet Borrelly and
has lived to tell every detail of its spine-tingling
adventure!” said Dr. Marc Rayman, the project manager of Deep
Space 1 at the Jet Propulsion Laboratory (JPL), Pasadena,
Calif. “The images are even better than the impressive images
of comet Halley taken by Europe’s Giotto spacecraft in 1986.”
Rayman added, “After years of nursing this aged and wounded
bird along — a spacecraft not structured to explore comets,
a probe that exceeded its objectives more than two years ago
— to see it perform its remarkably complex and risky
assignment so well was nothing short of incredible.”
“It’s mind-boggling and stupendous,” said Dr. Laurence
Soderblom, the leader of Deep Space 1’s imaging team, and a
geologist with the U.S. Geological Survey, Flagstaff, Ariz.
“These pictures have told us that comet nuclei are far more
complex than we ever imagined. They have rugged terrain,
smooth rolling plains, deep fractures and very, very dark
material.”
Scientists also realized that Borrelly was different than
they expected as Deep Space 1 flew through the coma, the
cloud of dust and gas surrounding the nucleus. They had
expected that the solar wind would flow symmetrically around
the cloud, with the nucleus in the center.
Instead, they found that though the solar wind was flowing
symmetrically around the cloud, the nucleus was off to one
side shooting out a great jet of material forming the cloud
that makes the comet visible from Earth. “The formation of
the coma is not the simple process we once thought it was,”
said Dr. David Young of the University of Michigan, Ann
Arbor, leader of the team that made the measurements. “Most
of the charged particles are formed to one side, which is not
what we expected.”
Deep Space 1 completed its primary mission testing ion
propulsion and 11 other advanced, high-risk technologies in
September 1999. NASA extended the mission, taking advantage
of the ion propulsion and other systems to undertake this
chancy but exciting encounter with the comet.
Deep Space 1, launched in October 1998 as part of NASA’s New
Millennium Program, is managed by JPL for NASA’s Office of
Space Science in Washington. The California Institute of
Technology manages JPL for NASA.
More information can be found on the Deep Space 1 Internet
home page at:
