A daring plan to have helicopters snag a space capsule as it plunged toward Earth went awry Wednesday when its parachutes failed to open and it slammed into the desert floor.

The catastrophic descent left the Genesis capsule (search) buried halfway underground and exposed its collection of solar atoms to contamination. The capsule held billions of atoms collected from the solar wind during a mission that was designed to reveal clues about the origin and evolution of the solar system.

Scientists were hopeful they could salvage the broken disks that held the atoms, and perhaps still unravel the mystery of the solar system.

"This is actually not the worst-case scenario," said Andrew Dantzler, director of NASA's (search) solar system division, noting the capsule embedded itself in soft desert soil and avoided hitting anything harder that would have made it a "total loss."

Flight engineers suspect a set of tiny explosives failed to trigger the capsule's parachutes, and the capsule slammed into the Utah desert at 193 mph.

Helicopters flown by Hollywood stuntmen were supposed to grab Genesis almost a mile above the Utah desert and lower it gently to the ground by snatching its parachute with a hook. But before the retrieval team learned of the parachute failure, the speeding capsule had plummeted into the Utah desert.

"There was a big pit in my stomach," said physicist Roger Wiens of Los Alamos National Laboratory (search), which designed the atom collector plates. "This just wasn't supposed to happen. We're going to have a lot of work picking up the pieces."

A recovery team that includes Genesis project members was dispatched to the crash site Wednesday afternoon on a salvage mission. It was uncertain whether the capsule could be brought quickly to a clean room for an inspection.

NASA planned to appoint a "mishap review board" within 72 hours that could take two to four months to determine a reason for the failure of the six-year, $260 million mission.

The spacecraft was designed and built by Lockheed Martin Space Systems near Denver. A company spokeswoman said engineers were beginning to analyze the failure with NASA, but had no immediate comment.

The Genesis mission, launched in 2001, marked the first time NASA has collected any objects from farther than the moon for retrieval to Earth.

Together, the charged atoms captured over 884 days on the capsule's five disks were no bigger than a few grains of salt, but scientists say that would be enough to reconstruct the chemical origin of the sun and its family of planets.

The five disks were of different thicknesses, which could make it easier for scientists to sort out shattered remnants and put pieces back together like a puzzle, Wiens said.

The solar wind is a stream of highly charged particles that are emitted by the sun. Scientists hoped the charged atoms gathered in the capsule -- a "billion billion" of them -- would shed important light on the solar system, said Don Burnett, Genesis' principal investigator and a nuclear geochemist at California Institute of Technology.

"We have for years wanted to know the composition of the sun," Burnett said before the crash. He said scientists had expected to analyze the material "one atom at a time."

Scientists had expected to study the material for five more years.

The mishap also raised questions about the durability of another NASA sample-return capsule called Stardust, due to land here in 2006. But that capsule was built to be more rugged and will land on its own with a parachute.