by Playfuls Staff |
9th January 2006
People have always been fascinated by comets, and by the ancient mysteries they might hold. Everyone remembers the highly spectacular “Deep Impact” mission, when scientist blew a hole in a comet, in order to gather information about the materials contained within. And now, another dust-collecting mission is about to reach its end.[more]
Thus, the first mission to fly to deep space and collect samples from a “cosmic traveler” will be returning home on Jan. 15, heading for the Utah desert.
As reported by the Washington Post, NASA's Stardust spacecraft flew two years ago through the halo of gas, dust and debris, or "coma," enveloping comet Wild 2, and on Sunday it will send a capsule containing the samples on a parachute descent into the U.S. Army's Dugway Proving Ground. Its sample compartments are filled with an ultra-frothy spun glass called aerogel, which has caught, and contains, thousands of particles of comet dust, virtually all of them considerably less than the width of a human hair.
Stardust has had a lot of challenges. Under NASA's cost-saving Discovery program, the project spent only $168.4 million, using off-the-shelf components where possible and a relatively small Delta II launch rocket for the 850-pound spacecraft.
The probe lifted off from Cape Canaveral Air Force Station on Feb. 7, 1999, "parked" in a holding orbit 115 miles above Earth for half an hour, then ignited its upper-stage rocket to escape Earth's gravity.
But Stardust traveled 2.1 billion miles over nearly five years to catch its quarry, Wild 2, a comet that originated beyond Pluto and migrated to the inner solar system after receiving a gravity push from Jupiter in 1974.
Stardust carried a two-sided, tennis-racket-shaped particle collector with about 100 small aerogel-filled compartments, "like a giant ice cube tray". Aerogel is 99 percent empty space, and has a unique capacity to "swallow" high-speed particles and bring them to a gentle stop without causing damage to either the particles or itself.
On each of Stardust's first two orbits, engineers deployed one side of the collector to catch interstellar dust, composed of tiny grains of material from beyond the solar system. Scientists can use these grains to study the composition of the stars where the particles originated.
The encounter with Wild 2 took place on Jan. 2, 2004. Engineers had opened the collector nine days earlier and had pointed the unused side in the direction of the comet's coma. When Wild 2 hurtled by Stardust at a relative speed of 13,684 mph, particles whooshed into the aerogel.
The spacecraft's cameras captured 72 images of the comet's surprisingly craggy cliffs, house-size boulders, pinnacles, craters and overhangs, and 20 jetlike "geysers" spewing gas and dust into space.
If everything goes according to plan, the Stardust spacecraft will release the 101-pound return capsule about 68,000 miles from Earth, then fire its thrusters to put itself into orbit around the sun. Four hours later -- at 4:57 a.m. Jan. 15 -- the capsule will arrive at the top of Earth's atmosphere at an altitude of 410,000 feet.
"Our return capsule is very small but very rugged," said project manager Tom Duxbury of the Jet Propulsion Laboratory, and it is unlikely to be critically damaged by the descent. Helicopters will fetch the capsule and bring it to a Dugway "clean room" where the sample collector will be removed, and samples will be taken to a laboratory for analysis. And then the real difficult work of making something of these particles will begin.
