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

In this story: Different comets, different personalities Lessons from asteroid rendezvous Building blocks of planets, life? RELATED STORIES, SITES

By Richard Stenger
CNN Interactive Staff Writer

March 6, 2000
Web posted at: 7:40 a.m. EST (1040 GMT)

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 going on."

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.

"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.

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."

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 water vapor.

"The gases we breathe, the water that we drink -- comets probably made a significant contribution to that," Veverka said.

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," Veverka said.

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