NASA's latest comet hunter won't be left in cosmic dust
Artist's concept of Contour as it approaches the nucleus of a comet
LAUREL, Maryland (CNN) -- A mission slated to fly by the nuclei of three comets won't be left in the dust like an earlier robot ship that sputtered near Halley, project managers promise.
The Comet Nuclear Tour (Contour) spacecraft should approach to within 100 km (62 miles) of two or three comets, cosmic chunks of ice and rock that scientists think could have served as building blocks for planets in the solar system and life on Earth.
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Mission managers plan to launch Contour aboard a Delta rocket
in July 2002. It will travel about 30 million miles (48
million km) from Earth to study the comets.
Onboard instruments will collect and analyze comet gases and
dusts while a camera obtains closeup photos of their nuclei.
Contour could also provide clues about how comets evolve and
how some of their ice evaporates when they approach the sun.
"When we see comets up in the sky they're really
spectacular," said Dr. Joseph Veverka of Cornell University,
the principal investigator for the mission. "But unless you
get close to a comet, you can't really figure out what's
Other comet missions
The Stardust spacecraft will collect comet dust and
interstellar dust particles during a close encounter with
Comet Wild 2 in 2004 and return it to Earth in 2006 for
scientific analysis. Launched in 1999, the NASA robot ship
began collecting interstellar dust in February 2000.
NASA's Deep Impact mission aims to crash a half-ton copper structure
into Comet Tempel 1, creating a huge crater and revealing the
internal composition of the comet. Deep Impact will launch in
2004 and use a camera and infrared spectrometer to collect
data on the icy spray from the crash, set to occur in 2005.
The Rosetta spacecraft will study the composition of the
comet Wirtanen and land a small probe on its surface. Rosetta
is scheduled for launch in 2003 and begin a two-year orbit of
the comet in 2012. On its long journey, the European Space
Agency spacecraft will also encounter a pair of asteroids in
2006 and 2008.
Only one spacecraft, the Giotto in 1986, has viewed a comet nucleus before. Launched by the European Space Agency, the robot ship studied Halley, a fairly young but well-known comet that zooms by the sun every 76 years from the outer depths of the solar system.
Giotto flew within 600 miles (1,000 km) of the comet but
lost much of its data during the final approach due to a
barrage of comet debris.
Different comets, different personalities
"Halley is very active with lots of dust," Veverka said. "We
intentionally chose one (comet) that produces a lot less gas
and dust. That will give us a better chance of carrying out
all the studies we want."
Contour will fly by Comet Encke in November 2003 and Comet Schwassmann-Wachmann-3 in June 2006 as they visit the inner solar system. It will take nucleus pictures at resolutions of 13 feet (4 meters), 25 times better than those from Giotto.
With different personalities, the two comets should offer
scientists clues about comet diversity. Encke is considered
an extremely evolved comet and has maintained a stable
orbit for thousands of years.
The less predictable Schwassmann-Wachmann-3, however, split
up into at least three pieces in 1995. Parts of its internal
structure could still be exposed.
The robot could then continue on, visiting Comet d-Arrest in 2008 or an as-yet undiscovered comet. That decision will depend in large
part on NASA funds, project managers said.
Sky watchers on the ground won't be left in the dark. When Contour makes its passes, the comets will be well situated in the heavens for astronomers to observe them.
Lessons from asteroid rendezvous
The $158 million mission received a major boost this month when NASA gave final approval to build the small, mostly solar-powered Contour ship.
With preliminary design review and independent assessment completed, mission engineers should begin building the spacecraft this month.
The Johns Hopkins University Applied Physics Laboratory (JUAPL) in Laurel, Maryland, is managing the project for NASA.
Mark Holdridge, the Contour operations director, said the spacecraft's designers have applied valuable lessons from the Near
Earth Asteroid Rendezvous (NEAR) mission, another JUAPL project. Earlier this month, NEAR became the first man-made satellite to orbit an asteroid.
For example, NEAR lost recorded information
when it powered down during a low voltage emergency. Contour
will make use of Flash memory, which is non-volatile and can
store data during a power outage, said Holdridge, also a member of the NEAR team.
The Contour will blaze by the comets at speeds between 31,000
and 62,000 mph (50,000 and 100,000 km/h), which makes
planning, design and testing critical parts of the mission.
The high rates of speed give project operators little room
for error. "It's a time critical operation," said Holdridge.
"It's either all or nothing (for each comet rendezvous). You
either get it or you don't."
Building blocks of planets, life?
Scientists think comets, which mostly reside beyond the
planets, can help unlock secrets about the origin of the
solar system and perhaps life on Earth.
Planets are thought to have been formed as comets and
asteroids grouped together billions of years ago.
"If you understand what comets are really made of, it will
tell you the original materials of the Earth," Veverka said.
The ancient ice balls could have originally provided gases
and liquids essential to life, like oxygen, nitrogen and
"The gases we breathe, the water that we drink -- comets
probably made a significant contribution to that," Veverka
Besides providing the conditions of life, comets could have
seeded the Earth with key ingredients in the primordial soup
from which life sprang.
Complex carbon molecules like amino acids, the building
blocks of life, could have originated from comets.
"The evidence is tantalizing but far from complete at this point,"
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Comet Nucleus Tour (CONTOUR)
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