The U.S. spacecraft "Stardust" has now begun a two-year journey back to Earth carrying pieces of a comet. The first-ever samples of a celestial body other than the moon were snatched during a dramatic flyby through the comet's tail last week. Yet the mission's spectacular success has to some degree been overshadowed by the successful 4 January landing on Mars by the "Spirit" rover.
London, 7 January 2004 (RFE/RL) -- In a remarkable operation taking place some 390 million kilometers from Earth, the U.S. robot spacecraft "Stardust" sailed through the tail of a comet -- a torrent of dust, ice, and gas particles -- and grabbed a small sample.
The spacecraft came within 240 kilometers of the rocky nucleus of the Wild-2 comet. A member of the "Stardust" science team, Thanasis Economou, described it to the Associated Press as something "like driving a car during a severe hail storm" -- but 100 times worse.
"Stardust" took photographs of the comet's heavily cratered surface -- the best comet pictures ever taken and "better than we had hoped for in our wildest dreams," according to project scientist Ray Newburn. The "ancient dirty snowball," as comets are called by astronomers, is also being subjected to probing by other instruments to help reveal the origins of our solar system.
Lucy Owens is assistant editor of the monthly "Spaceflight" magazine of the British Interplanetary Society. She described the significance of the mission by saying, "It is the first mission designed to bring back samples from a known comet, and the comets provide the best-preserved raw materials in the solar system, so [the] cometary and interstellar dust samples will help provide answers to the fundamental questions of the solar system."
Owens says the $200 million "Stardust" craft contains a device shaped like a tennis racket that is filled with a sterile, spongelike foam called aerogel. Thousands of particles from the comet stuck in the gel when "Stardust" passed through the comet's tail.
The samples are now in storage inside the spacecraft, along with samples of interstellar particles collected on the way to the comet. The samples will be returned to Earth in January 2006. Owens added that "Stardust" also took pictures of an asteroid it encountered just over a year ago, so it really has been a "remarkably successful mission."
"It is fantastic to have some good news, really, regarding a mission of this kind. Particles and dust will reveal [a rich mixture of things,] and I guess we are looking forward to 2006 when it lands -- I think it is in the Utah desert -- and scientists can begin to learn a lot more about the origins of the universe," she said.
Scientists are now processing the information gleaned from the cometary flyby and are studying some 70 detailed pictures taken of the comet's 5-kilometer-wide surface that show deep depressions, which appear to have been caused by the rapid evaporation of ice heated by the sun. The geysers or jets that spurt from these holes dissipate into the comet's tail, a thin veil of gas and particles that sometimes stretch for several million kilometers.
Dr. Richard Taylor is a member of the Probability Research Group, which studies solar-system phenomena. For him, the samples heading to Earth may also hold important clues to the origins of life.
"The whole 'Stardust' mission is really part of all our work of looking at, really, the origin of materials that led to life within the solar system. The important thing is that we do not have a fully detailed understanding of the nature of the original dust from which the planetary bodies condensed, [whether] this dust was fairly uniform or in fact varied from one place to the other in the solar system as it [was] forming," Taylor said.
Comets, Taylor says, contain matter dating from the origins of the universe, which is why the samples are so important. "We are now aware that the very first generations of objects, which were larger than any stars we have now and which detonated very early on, produced more than enough of the heavy elements that are necessary to provide the basic requirements of life -- elements we condense into the lovely acronym CHENOPS, which simply stands for carbon, hydrogen, nitrogen, oxygen, sulphur and phosphorus," he said. "These are present in every form of life, no matter what it is, and they have been present in sufficient quantities for microbial life to exist in the universe since almost the time it began."
Taylor believes there could be microscopic life preserved inside comets, since some scientists think comets may have helped to spread life throughout the solar system. He feels that microscopic life is likely to be found on most bodies in our solar system, but deep beneath the surface, where it can be protected from radiation and other hazards.
This, he said, is "almost certain. At least 10 of the bodies in the solar system -- ranging from the polar regions around Mercury, out to the satellite of Pluto -- have subsurface conditions in which microbial life can exist. On Earth, 56 percent of all the mass of life is microbial, very deep under the surface."
Taylor says he's very happy that the "Stardust" spacecraft -- launched back in 1999 -- survived its encounter with Wild-2. But he says he's very impatient to see what the samples may reveal.
As project manager Tom Duxbury said: "We took a spacecraft and flew it five years. But in these five years, we went back to the origin of time -- to the origin of our solar system."
(More information and photographs can be found on the Internet at http://stardust.jpl.nasa.gov)