It's T-minus two days, and University of Washington astronomer Don Brownlee can't help but think about things that could go wrong. A solar flare could...

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It’s T-minus two days, and University of Washington astronomer Don Brownlee can’t help but think about things that could go wrong.

A solar flare could zap the spacecraft as it approaches Earth.

The parachutes might fail, causing the capsule and its cargo of comet dust to smash into the Utah desert and shatter like an egg.

Tracking antennae could blink out, leaving no way to locate the vessel as it approaches the end of its nearly 3 billion-mile journey.

In the seven years since the NASA probe Stardust was launched, Brownlee has had ample opportunity to envision disaster. But he has also held fast to the dream of success that inspired the bold mission to grab particles from a comet and bring them back to Earth.

That dream could be realized before dawn Sunday, when the capsule is scheduled to land — gently — at a sprawling military test range southwest of Salt Lake City. It would mark the first time an American mission has returned solid material from space since Apollo 17 hauled moon rocks more than 30 years ago.

More about Stardust

The Stardust capsule will create a fireball as it plummets through the Earth’s atmosphere, but the brief show probably won’t be visible in Washington. People in southern Oregon, Northern California, Idaho, Nevada and Utah may be able to see the pinkish light, which will glow brighter than Venus.

Observing tips and maps can be found at http://reentry.arc.nasa.gov/

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Commentary, images and briefings will be broadcast live on NASA TV beginning at 1:30 a.m. Sunday. NASA TV is available on some cable networks and online at www.nasa.gov/

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More information on Stardust is at http://stardust.jpl.nasa.gov/

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The scant teaspoon of particles Stardust carries will be the closest mankind has ever come to touching the primordial stuff of the solar system.

Brownlee, the mission’s principal investigator, calls it ground truth.

The microscopic bits of the comet, dubbed Wild-2, will reveal new detail about the chemical building blocks of the sun, the planets and all living things. Theories about the solar system’s birth must mesh with those findings. So, too, must ideas about comets seeding Earth with water and the basic ingredients for life.

“It’s somebody getting out on the ground and checking to see if the theories hold up,” Brownlee said.

Ground truth is a rare commodity among astronomers, most of whom spend their lives studying impossibly distant stars and galaxies. But Brownlee has always practiced a hands-on form of science — though never before on so grand or nerve-racking a scale.

“Space is an exceedingly nasty business,” he said in his office overlooking Portage Bay. “You can do everything right and at any second, any second, things can go bad.”

Cooking rocket fuel, building missiles

Despite its perils, Brownlee is clearly captivated with the cosmos.

Posters of Neil Armstrong’s moonwalk and Jupiter’s Red Spot decorate his office walls. He reels off the names of astronauts and space programs with the reverence of a baseball fan reminiscing about the 1927 Yankees.

In the techno-mania that gripped the United States after the Russians launched Sputnik, Brownlee was one of those kids who cooked rocket fuel on the kitchen stove and built missiles out of pipe. He nearly burned down the garage of his family’s home in the Berkeley hills with a homemade Van de Graaf generator — a sphere that generates enough static electricity to stand your hair on end.

At 62, he still frequents fireworks stands, searching for the biggest possible bang.

As an astronomer interested in the origin of the solar system, Brownlee has also long sought the biggest possible research bang: a comet mission.

Balls of ice and dust, comets are thought to be what was left over when gas and dust coalesced to form the sun and planets. In the intervening 4.5 billion years, Earth and the planets have been morphed by heat, gravity and other forces. Comets, which spend most of their time in the icy reaches near Pluto, are comparatively unchanged.

“These are things that have truly been stuck in the deep freeze since the formation of the solar system,” Brownlee said.

But it took him and his colleagues nearly 25 years to persuade NASA to visit a comet. Several missions were planned then scrapped, including an ambitious rendezvous with Comet Halley in 1986.

Now, comet research is enjoying a heyday. Last summer’s Deep Impact mission fired a probe into a comet, photographing and analyzing the debris. And Stardust has already sent back the best comet close-up shots ever taken.

Curiosity and audacity

Brownlee loves to talk. His conversations ricochet as one topic after another grabs his imagination. He can describe the foot pedals that propel his recumbent kayak or Stardust’s elaborate trajectory with equal enthusiasm.

But he also has the ability to focus with intensity on a single subject.

Brownlee and Peter Tsou, of NASA’s Jet Propulsion Laboratory, worked 15 years to design a collector that could capture comet particles traveling 13,000 mph without vaporizing the fragile grains — or being destroyed itself.

The breakthrough came when Tsou, Stardust’s deputy-principal investigator, hit on a material invented in the 1930s called aerogel.

“It’s about 99 percent air,” Brownlee said, holding out a blue, translucent cube in the palm of his hand. He and Tsou fashioned grids from the material and tested them in the lab. Particles moving faster than high-powered rifle bullets burrowed into the aerogel then stopped — intact.

Brownlee has been tackling similar technical challenges throughout his career. He is one of the nation’s top astronomers because he has limitless curiosity, the creativity to devise ingenious experiments and the audacity to put them into action, said Paul Hodge, Brownlee’s first astronomy professor.

Most students who took Hodge’s class at the University of California, Berkeley, in 1964 wrote reports for their class projects. Brownlee launched weather balloons, hoping to collect cosmic dust 100,000 feet above the ground.

“People had talked about it before,” said Hodge, now an emeritus professor at the UW. “But nobody had ever done it.”

That it didn’t work hardly mattered.

When Hodge moved to Seattle, Brownlee followed to become the UW’s first astronomy graduate student.

The hunt for space dust

Hodge got Brownlee hooked on space dust.

Scientists had long known the solar system was full of the stuff — and that it must include comet particles and other primordial bits. Bigger chunks fall to Earth as meteorites, but the fiery plunge through the atmosphere scrambles their chemical structure. Smaller particles waft down unscathed, like feathers.

Up to 40,000 tons of this microscopic flotsam rain down on the Earth each year.

The trick is finding it.

Hodge and other scientists had tried various schemes to collect particles, including a type of fly paper. They were foiled by soot and other earthly contaminants.

Brownlee succeeded by rigging a balloon with a device he called the Vacuum Monster. Powered by rocket fuel, it sucked in air at half the speed of sound. On its first mission, the contraption soared 130,000 feet and snagged the first extraterrestrial particle ever collected in the atmosphere.

Later, Brownlee designed a magnetic muck rake to mine the ocean floor for tiny, metallic space spheres and built a collector that was flown on high-altitude U-2 planes retired from spying.

Back in the lab, Brownlee uses a diamond-blade microtome to carve slices from specks a sixth the diameter of a human hair. Powerful electron microscopes allow him to zero in on a kaleidoscope of minerals and crystals.

It’s a treasure hunt. Every fresh particle offers a glimpse of a dizzyingly distant past.

“He fundamentally wants to know what things are made of,” said his friend Peter Ward, a UW paleontologist.

Compared with the isolated particles Brownlee has been able to pluck from the sky and sea floor, Stardust’s payload represents the mother lode of extraterrestrial matter.

“When we open it up,” he said with awe, “we will see something nobody has ever seen before.”

Asteroid named for him

A scaled-up model of a piece of space dust sits on a filing cabinet in Brownlee’s office.

It looks like millions of grains of black sand glued together. “We think the comet dust will look like this, too,” he said, holding it up to the light like a jewel.

He doesn’t mention that the class of particles is named for him. So is an asteroid. In 1995, he was voted into the National Academy of Sciences, America’s most elite scientific society.

As principal investigator, Brownlee has ultimate authority over the $212 million Stardust mission. His scientific clout is one of the reasons the comet mission beat out 27 competing proposals for funding under NASA’s Discovery program of “faster, cheaper, better” space projects, said longtime collaborator John Bradley, of Lawrence Livermore National Laboratory. Yet in a recent group shot, Brownlee is barely visible in the back.

Prominent scientists usually attract critics, but Brownlee has few.

Perhaps his most controversial move was to co-author a popular science book with Ward, the UW paleontologist, that argues Earth is one of the only places in the universe where complex life could have evolved. “Rare Earth” earned Brownlee and Ward a modest celebrity but also attracted polite skepticism from colleagues who think they didn’t consider the many forms life might take in other worlds.

Sharing ups and downs

Among those more optimistic about the existence of other civilizations is Brownlee’s wife, Paula Szkody. Also a UW astronomer, Szkody studies star pairs hundreds of light-years away.

The couple met in graduate school.

With his weather balloons and microscopes, Brownlee wasn’t as bookish as most of their fellow students, she recalled. He wooed her with camping trips and a 3 a.m. outing to look for a passing comet.

They live five minutes from the university on Portage Bay, in a cedar-shingled houseboat built in 1915. When Brownlee began planning Stardust, their daughter had just started middle school and their son was in grade school. Allison now works as an environmental scientist, and Carson is about to graduate with a computer-science degree.

The entire family shared in the mission’s highs and lows, from the spacecraft’s flawless performance during its encounter with the comet, to the time a massive solar flare left the vehicle spinning blindly in space.

Another bad day came two years ago when the capsule from a solar wind mission, also designed and built by Lockheed Martin, crashed and shattered when its parachutes malfunctioned. Brownlee’s team conducted an exhaustive review and concluded Stardust doesn’t share the same faulty wiring. But they also laid backup plans to dig the pieces out of the ground, if necessary.

At this point, about all Brownlee can do is check weather reports, replay worst-case scenarios in his mind and wait.

He also has pondered the fate of the Stardust spacecraft after it jettisons its capsule.

Always eager for pyrotechnics, Brownlee wanted to let it burn up in the atmosphere. NASA nixed that idea. Instead, thrusters will send the vehicle into an orbit around the sun that will probably eject it from the solar system in a million years or so.

Brownlee, who is used to thinking on time scales that make most people queasy, smiles at that idea. It means that billions of years from now, after the sun becomes a red giant and incinerates the Earth, Stardust will still be floating through the galaxy.

Sandi Doughton: 206-464-2491 or sdoughton@seattletimes.com