After traveling 1.5 million kilometers beyond Earth to obtain bits of the solar wind, NASA's first automated sample-return mission, Genesis, ended in a crash in the Utah desert on September 8. Researchers do not know just why the parafoil failed to deploy, but they say they feel confident that they can still accomplish the major goals of the mission despite the damaged capsule. Any conclusion stemming from the mission, however, may remain dubious because of the mere possibility of contamination.
Genesis had onboard an estimated 20 micrograms of solar-wind particles collected over three years in space. These particles came from the sun's visible surface, called the photosphere. Ninety-nine percent of it consists of the original material from the primitive nebula that coalesced into the sun and planets; an analysis of the samples would therefore provide a baseline of information about the building blocks of our solar system.
The original retrieval plan had called for a helicopter to snag Genesis's parachute in midair. Once secured, the capsule would have been placed in a specialized shipping container and transported to a clean room at the NASA Johnson Space Center in Houston.
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But because the parafoil failed to open, Genesis slammed into the desert at 311 kilometers an hour, half-burying itself. On impact, sand, dust and other contaminants entered the capsule. Engineers carefully excavated it and brought it to the nearby U.S. Army Dugway Proving Grounds, where an initial inspection with mirrors revealed a 7.6-centimeter-wide hole in the sample container. Peering inside revealed more bad news: many of the hexagonal wafers, which collected the solar-wind samples, were broken. (Genesis carried a total of 275 sample wafers, each 10 centimeters on a side, placed on five collector arrays.) Broken up, they were even more directly exposed to contamination.
Roger Wiens, project flight payload leader for Genesis, notes that "this kind of contamination can overwhelm the amount of signal we have in the solar-wind sample. We will certainly be doing some cleaning of the samples, probably with ultrapure water." Wiens says that the particles get embedded in the wafers to a depth of about 50 nanometers and that the penetration might provide some protective distance from small amounts of surface contamination. Bruce Barraclough, a principal investigator on the Genesis mission, remains optimistic: "I am sure that some, if not most, of the science will be able to be recovered from the samples."
Gilbert V. Levin, a former astrobiologist on two NASA Mars missions, thinks the Genesis team is mistaken. "It is unlikely that any such sample recovery will be without controversy," remarks Levin, now chairman of Spherix, a Beltsville, Md., biotechnology company. He points to the Martian meteorite ALH 84001 as an example. In 1996 some scientists concluded that fossilized forms of unusual bacteria were inside; however, other researchers attributed the forms to earthly contamination. The Martian debate "is a strong harbinger of the same issue arising with the Genesis material," Levin says.
Meanwhile determining the cause of the crash will take several months, and how the incident might affect future sample-return missions is unclear. An investigation might prove useful for NASA's Stardust craft, which is carrying precious samples of comet Wild 2. It will land on Earth on January 15, 2006. Although no midair retrieval is planned--Stardust is less sensitive to shock than Genesis--the capsule will still rely on a parachute. According to Stardust principal investigator Donald Brownlee, the sample-return capsule has parachute-releasing pyrotechnic charges similar to those that failed on Genesis. "One thing the Genesis team is looking at is the temperature readings from the battery area on the spacecraft while it was gathering samples," Brownlee states. The sun may have cooked the batteries, causing them to malfunction. So far the Stardust team has not observed any temperature anomalies with the craft's batteries. Concerns will remain high, however, until the Genesis investigation board finds out exactly what went wrong.
