Calling all stunt pilots to catch solar dust

Somewhere over a wide stretch of Arizona desert Thursday morning, the Jet Propulsion Laboratory will perform its best impersonation of James Bond.

For a scientific facility best known for shipping six-wheeled rovers to Mars and flinging probes to the far corners of the solar system, the terrestrial exercises might seem a bit mundane. Then again, none of those missions ever involved stunt pilots or helicopters snatching a space probe from mid-air.

If all goes as planned, two helicopters will do just that - sort of. Actually, Thursday is just a test run for the real thing, which will take place in September, but it is one of the final steps toward a feat that has never been attempted in the name of science.

The dramatic catch is necessary because of this mission's precious cargo: samples of solar dust that must not be shaken or stirred by a rough landing.

But it also marks a frontier in space exploration.

This will be the first sample of space material returned to Earth since Apollo 17 came back from the moon in 1972.

Other samples, however, will follow - from comets and asteroids and even Mars - as scientists seek to bring extraterrestrial materials back to Earth, where the full array of scientific instruments can be brought to bear on every rock and cosmic mite.

"This is just the beginning of a new era," says Don Burnett, the mission's chief scientist.

The advantages of bringing samples back to Earth-bound labs has been highlighted during the current rover mission on Mars. The two rovers are the most sophisticated machines ever sent into space, carrying spectrometers and sensors on a cart that can trundle up slopes and over rocks.

In three months, they have established a scientific record unprecedented in scope and detail. On Earth, however, a geologist could probably do the same thing in an afternoon.

So the idea is to bring the interesting stuff back. And that's where the helicopters come in.

The Genesis probe, when it finally arrives Sept. 8, will bring samples of the solar wind. But it will need a soft landing, or two years of data could be turned into a potluck of parts and particles. Genesis will fizz into the atmosphere like the manned capsules of old with a heat shield to keep the probe from burning up and a parachute to slow its entry down to a gentle drift.

Helicopters will be dispatched to a specific staging area depending on where the probe is last tracked, and will then lift off to scour the skies. In Thursday's training run, the staging area will be in the Yuma Proving Ground on the border with California. On Sept. 8, the real probe will come down in the Utah Test and Training Range, northwest of Salt Lake.

The drill will be the same Wednesday as in September, though. When the pilots - stunt and military pilots by training - locate the probe, one helicopter will sweep up behind it and snatch the parachute with a special hook that fastens shut with explosive bolts. The other helicopter will stand by as backup.

Decades ago, during the early days of the space race, military jets did much the same thing, capturing film canisters that had been jettisoned by spy satellites and left to parachute through Earth's atmosphere. Since then, though, helicopters have made the process easier, and mission planners expect no problems. Instead, they hope that success will lead to bigger things.

Sample returns are already planned for a comet and an asteroid this decade, and the rovers' discoveries on Mars have scientists talking about bringing back pieces of the Red Planet next decade.

For its part, Genesis turned its face to the Sun. For two years, it orbited around an empty point in space between the Earth and Sun - the point where gravity from each are balanced.

It unfolded tennis-racket shaped arms that held wafers of gold, sapphire, silicone, and diamond. The wafers collected particles that streamed by on the solar wind - the constant flow of solar dust and detritus that courses into the outer reaches of the solar system.

All told, the particles should weigh no more than a few grains of salt, but they could unlock the mysteries of how the Sun and planets formed.

So far, scientists have only been able to theorize about the composition of these materials. Knowing for certain will open a window on the past because the materials in the solar wind come from the surface of the sun, which is the only part of the solar system that has remained largely unchanged since it was formed. That makes Genesis a time capsule holding 4.5 billion-year-old clues as it heads back toward Earth.

"This is something we've been waiting for," Dr. Burnett says, "for quite a few years."