Scientists are chomping at the bit for tomorrow's Earthly return of a sample capsule from NASA's Genesis spacecraft, hoping the star stuff it carries will help answer questions on the origins of the solar system and we who live in it.

After more than three years in space, the Genesis capsule has collected samples of solar wind blown from the Sun and is poised for a daring mid-air capture by a hook-laden helicopter above the Utah desert Tuesday morning.

If all goes well, the capsule and its precious pieces of the Sun will be delivered into the waiting arms of mission scientists before lunch.

"We have one parachute between us and being able to do what we want to do," said Don Burnett, Genesis principal investigator at the California Institute of Technology, in a telephone interview. "The mission starts when we get back on the ground."

Burnett, a researcher at the California Institute of Technology in Pasadena, and other mission researchers are eagerly looking forward to studying the composition of elements and isotopes within the Genesis samples. Because the material came from the Sun, they say, it represents the most pristine form of matter in the solar system since its formation.

"What we've been missing is the starting point," said David Lindstrom, program scientist for the Genesis mission at NASA headquarters in Washington D.C. "The first [goals] are to learn how the Sun and its family of planets originated and determine how the solar system evolved."

The mission marks the first time in three decades NASA has returned space samples to Earth.

Snatching solar wind

Launched in July 2001, the Genesis spacecraft has spent the bulk of its time orbiting a region known as Lagrange point, a point between the Earth and Sun where the gravitational pull from both objects balances out.

For more than two years during its flight, Genesis exposed a series of collector plates designed to trap solar wind particles that strike them.

"We'll bring back a few micrograms embedded in these plates," said Bob Corwin, recovery systems engineer for Lockheed Martin, which built the spacecraft.

The collector plates are made of extremely pure material, primarily silicone but also synthetic diamonds, to make it easier for researchers to isolate the tiny particles of solar wind from their surroundings, Corwin added.

Atoms at a time

Although Genesis is returning a seemingly tiny amount of material, scientists expect to be drowning in solar samples.

"We've got to think in terms of atoms," Burnett said, adding that the micrograms of solar wind could contain billions of individual particles on the atomic level. "So you see, we have a lot to go around.

Genesis researchers said the wind samples snatched by their spacecraft can be representative of the solar system when it was still a solar nebula, a vast cloud of interstellar gas and dust 4.5 billion years ago before the Sun or planets formed.

"All the matter in the solar system, including us, was part of this vast cloud," Burnett said, adding that the nebula eventually coalesced into a whole range of different planetary material. "We want to understand how that happened."

Until now, researchers have had to rely on remote observations of stars using telescopes to study target spectrums that then yield information on an object's composition. Through Genesis, however, astronomers expect a look at have an up close look at that material in their own lab.

The research program is planned through 2008.

Genesis vs. Stardust

While researchers are eager to get their hands on the Genesis samples, they are also looking forward to compare their results with future space sample return efforts like NASA's Stardust mission.

Stardust, which is bring back samples of the comet Wild 2 in 2006, will allow researchers to the chance not only to compare solar wind particles with those from an icy body from the depths of space, but also with Earth and lunar material as well.

"Stardust and Genesis are brother and sister," Burnett said, adding that the two missions give astronomers a peek at material from both ends of the solar system. "Our planetary knowledge is highly biased because we have sampled only things from the inner solar system...the Moon, Earth, Mars."

Meanwhile, Genesis researchers plan to hit the ground running. Once helicopters snag the Genesis sample return capsule from the sky, it will be taken to makeshift clean room at Michael Army Air Field near Dugway Proving Ground in Utah. There, waiting researchers check the container before sending it down to a dedicated clean room Johnson Space Center in Houston for further study.

"With some luck, we'll have something to report in six months," Burnett said.