[meteorite-list] On The Trail of Cosmic Mysteries, Stardust Heading Home

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Jan 9 00:18:06 2006
Message-ID: <200601090516.k095GSq05424_at_zagami.jpl.nasa.gov>

For JPL internal use only.

http://seattlepi.nwsource.com/local/254746_stardust06.html

On the trail of cosmic mysteries, Stardust heading home
Craft carrying tiny particles with big secrets heads home

By TOM PAULSON
SEATTLE POST-INTELLIGENCER REPORTER
January 6, 2006

In about a week, a space capsule carrying the oldest material in the
solar system will create a night fireball as bright as the moon,
potentially visible from Washington to Utah, as it re-enters the
atmosphere faster than any other man-made object has ever returned to
Earth.

Everyone is hopeful the parachutes will open this time.

"It's hard to convey to people how tense these situations can be," said
University of Washington astronomer Don Brownlee, principal scientist
for NASA's Stardust mission.

Stardust mission

On Jan. 15, at 2:12 a.m. PST, Brownlee and his colleagues hope to
celebrate the successful touchdown in the Utah desert of a 100-pound
space capsule that will set all sorts of astronomical science and space
exploration records -- the first deep space sample return, the farthest
return trip of any spacecraft (nearly 3 billion miles) and the fastest
re-entry speed (28,000 mph when it first hits the atmosphere).

And that doesn't even begin to describe the potential scientific
breakthroughs to come from studying the collected dust of a pristine
comet and other interstellar particles.

The tiny particles contain big secrets. They are thought to hold the
original materials from which everything in our solar system, including
life, was created.

But before the science begins, they have to get Stardust's precious
cargo back on Earth safe and sound. The last NASA space capsule to
"land" at the same place, the Air Force Utah Test and Training Range
southwest of Salt Lake City, was the Genesis probe in September 2004.
Genesis' parachutes failed to deploy, and it smashed into the desert
floor, cracking open and contaminating some of its cargo of collected
solar wind particles. NASA officials say they are confident that
Stardust's parachutes will not fail, despite the fact that Lockheed
Martin Space Systems built both spacecraft and their chute systems.

Brownlee shrugged off the concerns, noting Stardust's parachutes are
different, simpler, so there's less to go wrong. Besides, he added, "We
really have no control over it anyway once it starts coming back in."

Launching the $212 million Stardust spacecraft Feb. 7, 1999, was much
more nerve-racking, Brownlee said. Launches have a 95 percent success
rate, he noted, which from a grimmer perspective means they don't
succeed one out of every 20 times.

When Stardust first went up, the radio signals from the craft began
fading. Everyone went silent, Brownlee said, until the signals returned.
Then, he said, there were indications the spacecraft was starting to
fire some of its thrusters (made in Redmond by what was then Primex, now
Aerojet) willy-nilly -- technically, "uncommanded thrusting."

About Stardust

"It felt like the whole thing was on the verge of disaster," Brownlee
said. "There was this guy with his finger on a button to blow the
vehicle up if it went off range. ... No one said anything for minutes."

Then, somehow, Stardust pulled itself together, began operating as
expected and headed off on its interplanetary journey to rendezvous with
a comet named Wild 2 (pronounced "vilt") that recently had come in from
the edge of our solar system.

The mission since then, Brownlee said, has been amazingly glitch-free
and has already produced new insights into comets. When Stardust finally
encountered Wild 2, on Jan. 2, 2004, the spacecraft was able to shoot
some close photos of the comet.

"They were spectacular and surprising," Brownlee said.

Wild 2 didn't look like it was supposed to, according to standard
theory. Distant analyses of other comets such as Halley's had led
scientists to think of comets as loose, unstructured piles of ice, dust
and rocks. Wild 2 had craters and spires hundreds of feet tall --
indicating a firm structure. Numerous gas jets were shooting out of it.

"It was really weird-looking," Brownlee said.

But the real scientific prize was obtained not by looking, but by snatching.

"The primary purpose of the Stardust mission was to collect comet dust,
the most basic material of the solar system, and bring it back to Earth
for study," said Brownlee, as if repeating the proposal he made to NASA
more than a decade ago.

The UW astronomer, a member of the National Academy of Sciences, is
world-renowned for his work studying cosmic dust, interstellar particles
-- stardust. But all of the particles studied so far have been collected
relatively close to home.

Earth's proximity to the sun alters these particles, chemically and
physically.

Brownlee wanted to get his hands on some pure stardust, the
unadulterated material from which everything -- including life itself --
was created.

"Virtually all of the atoms in our bodies came from the kind of grains
we collected from the comet," he said. Billions of years ago, he said,
our solar system was mostly a swirl of comets and cosmic dust that
eventually aggregated into stars and planets.

But exactly how this happened, how the solar system came to be, how the
Earth formed to retain a little water (and, relative to the size of our
planet, the water is just a thin film), how biological life first came
about and all the rest, Brownlee said, is still not fully understood.
The public paid little attention to Stardust when it encountered the
3-mile-wide Comet Wild 2 in 2004, likely because of competing space news
that NASA's Mars rover Spirit was about to land for an extended hike
about the red planet. But many in the scientific community were more
focused on Brownlee's spacecraft, anxiously waiting to hear if it
succeeded.

The best way to imagine what it took for Stardust to capture and
preserve the comet dust is to think of a ballet dancer being shot from a
cannon into an active combat zone and told to execute a perfect "tours
en l'air" while getting sandblasted.

The spacecraft approached to within 150 miles of Wild 2, flying through
the coma -- the cloud of dust, gas and water vapor at the front of the
comet. Most of the spacecraft was shielded from the particles striking
it at high speeds. But one instrument, a tennis-racket shaped collector,
was exposed to meet the particle storm head on.

In this instrument were trays of aerogel, an aerosolized glass-like
substance that is the lightest solid material on Earth (99.8 percent air
trapped in a silicon framework). Based on flyby measurements taken at
the time of the space rendezvous, Brownlee and his colleagues believe
the aerogel captured thousands of comet particles. Scientific teams
around the world have been promised samples and are eagerly awaiting
Stardust's return.

Once the capsule is recovered, the UW astronomer and his colleagues will
head to NASA's Johnson Space Center in Houston where it will be opened
inside a clean room. Some observations could be made within days, but
study will go on for years, perhaps decades.

Will Wild 2 provide startling new insights about our origins? Will the
dust have more than simple carbon molecules? Could we find more complex
biological precursors, say a helical molecule or some other chemical
clues as to where we came from?

The Joni Mitchell song "Woodstock," which contains the lyrics "We are
stardust" and which, besides being golden, we are "billion-year old
carbon," also says:

"I don't know who I am, but you know life is for learning."

"This is when the real science begins," Brownlee said. "And I wouldn't
be surprised if what we find includes some surprises."
Received on Mon 09 Jan 2006 12:16:26 AM PST