IN DEPTH: New Life for Old Probes

Nov. 13, 2006 — For scientists planning a trio of new space missions, the hard part already is over: The probes are safely in space.

Idling in orbit since their complementary comet missions, NASA's Deep Impact and Stardust space probes may soon have new leases on life.

The space agency last week approved funding to develop two follow-on missions for Deep Impact, which blasted a projectile into the core of Comet Tempel-1 in July 2005, and one extension flight for Stardust, which this year returned samples of Comet Wild-2 that were collected during a January 2004 close encounter.

Deep Impact, Take Two

If the new missions are approved, Deep Impact would use its three working science instruments and remaining fuel for an extended flyby of Comet Boethin in December 2008.

"This mission is a very cost-effective way to provide new results that can be directly compared to the Deep Impact findings," said project lead scientist Michael A'Hearn, with the University of Maryland.

Researchers have been surprised by the diversity of the few comets studied to date — an indication the icy objects, which are believed to be leftover remains from the formation of the solar system, evolved differently.

"Even on Tempel 1, the comet we've imaged the best, there is shocking variability in its surface," A'Hearn said.

Scientists want to know what comets originally looked like and what happened to them as they traveled through space. The information is key to understanding if comets did indeed deliver the organic molecules that ultimately gave rise to life on Earth, as many researchers suspect.

En route to its new target, the spacecraft would have another mission unrelated to comets. A team of scientists led by Drake Deming at NASA's Goddard Spaceflight Center in Greenbelt, Md., wants to use Deep Impact to look for Earth-like planets around stars in other solar systems.

The scientists would use Deep Impact's electronic camera to measure photons of light radiating from stars already known to have giant Jupiter-class planets in orbit.

The instrument is sensitive enough to not only detect the big planets' passage in front of their mother stars, but even relatively tiny, Earth-like worlds.

If approved, the two Deep Impact extension missions would cost NASA up to $70 million — less than a quarter of the original mission cost. The contracts recently awarded were for $250,000 per project.

Stardust Returns

NASA also approved funding to develop a mission to send Stardust back to Deep Impact's original target to see what the comet looks like since it was gouged by an 800-pound projectile that smashed into the comet's nucleus with the force of 4.5 tons of dynamite.

Several months after the impact, Comet Tempel 1 made its closest approach to the sun. The higher temperatures may have also changed the comet's surface.

It's not just comets that have caught NASA's eye. Managers awarded $1.2-million study contracts for three missions, including an asteroid sample return flight closely patterned after the original Stardust flight.

Asteroids, Then and Now

Like comets, asteroids also could have showered early Earth with organic materials as they smashed into the planet's surface.

Scientists, led by Michael Drake with the University of Arizona in Tucson, would like to send a probe to asteroid RQ36 — a former main belt asteroid that now orbits the sun in a path that brings it relatively close to Earth.

"This is the sort of object that might have delivered organic material to Earth," Drake said.

One of the primary goals of the mission would be to acquire pristine samples of organic material for detailed studies in laboratories on Earth.

"We're looking for the building blocks of life. We don't expect to find a strand of DNA," said Dante Lauretta, the deputy principal investigator also with the University of Arizona. But "we've never been able to show that the building blocks of DNA and RNA could have an extraterrestrial source."

The asteroid also may have resources that could be used by future astronauts for water, fuel and construction.

NASA plans to redirect its human space program from microgravity research carried out in low-Earth orbit aboard the space station to exploration of the moon, Mars and other bodies.

"Asteroids may be the next place people go," Drake said. "Some of them are easier to get to than the moon."

If selected, the mission would be launched in 2011 and rendezvous with the asteroid in 2013.

Study contracts also were awarded for missions to probe the chemistry of Venus' oppressive atmosphere and to study the interior structure and history of Earth's moon.