[meteorite-list] Public to Look for Dust Grains in Stardust Detectors

[Ron Baalke]

Media Relations
University of California-Berkeley

Media Contacts:
Robert Sanders
(510) 643-6998, (510) 642-3734

FOR IMMEDIATE RELEASE: Tuesday, January 10, 2006

Public to look for dust grains in Stardust detectors
By Robert Sanders, Media Relations

BERKELEY -- Astronomy buffs who jumped at the chance to use their home 
computers in the SETI at home search for intelligent life in the universe 
will soon be able to join an Internet-based search for dust grains 
originating from stars millions of light years away.

In a new project called Stardust at home, University of California, Berkeley, 
researchers will invite Internet users to help them search for a few dozen 
submicroscopic grains of interstellar dust captured by NASA's Stardust 
spacecraft and due to return to Earth in January 2006.

Though Stardust's main mission was to capture dust from the tail of comet 
Wild 2 -- dust dating from the origins of the solar system some 4.5 
billion years ago -- it also captured a sprinkling of dust from distant 
stars, perhaps created in supernova explosions less than 10 million years 
ago.

"These will be the very first contemporary interstellar dust grains ever 
brought back to Earth for study," said Andrew Westphal, a UC Berkeley 
senior fellow and associate director of the campus's Space Sciences 
Laboratory who developed the technique NASA will use to digitally scan the 
aerogel in which the interstellar dust grains are embedded. "Stardust is 
not only the first mission to return samples from a comet, it is the first 
sample return mission from the galaxy."

"Like SETI at home, which is the world's largest computer, we hope 
Stardust at home will also be a large computer, though more of a neural 
network, using brains together to find these grains," said Bryan Mendez of 
the Center for Science Education at the Space Sciences Laboratory. Mendez 
and Nahide Craig, assistant research astronomer at the laboratory, plan to 
create K-12 curricula around the Stardust at home project and to reach out to 
local astronomy groups to boost participation.

Mendez and Craig will describe their educational outreach program in a 
poster session on Jan. 10 at the national meeting of the American 
Astronomical Society in Washington, D.C.

Based on previous measurements of interstellar dust by both the Ulysses 
and Galileo spacecrafts, Westphal expects to find approximately 45 grains 
of submicroscopic dust in the collector, a mosaic of tiles of lightweight 
aerogel forming a disk about 16 inches in diameter -- nearly a square foot 
in area -- and half an inch thick. Though those searching for pieces of 
Wild 2's tail will easily be able to pick out the thousands of cometary 
dust grains embedded in the front of the detector, finding the 45 or so 
grains of interstellar dust stuck in the back of the detector won't be so 
easy.

Thanks to a grant from NASA and assistance from the Planetary Society, 
however, Westphal and his colleagues at the Space Sciences Laboratory have 
created a "virtual microscope" that will allow anyone with an Internet 
connection to scan some of the 1.5 million pictures of the aerogel for 
tracks left by speeding dust. Each picture will cover an area smaller than 
a grain of salt.

"Twenty or 30 years ago, we would have hired a small army of microscopists 
who would be hunched over microscopes focusing up and down through the 
aerogel looking for the tracks of these dust grains," said Westphal. 
"Instead, we developed an automated microscope to scan the aerogel and 
hope to use volunteers we have trained and tested to search for these 
tracks."

The Web-based virtual microscope will be made available to the public in 
mid-March, even before all the scans have been completed in a cleanroom at 
Houston's Johnson Space Center. In all, Westphal expects to need some 
30,000 person hours to look through the scanned images at least four 
times. Searching each picture should take just a few seconds, but the 
close attention required as the viewer repeatedly focuses up and down 
through image after image will probably limit the number a person can scan 
in one sitting.

To insure that the volunteer scanners know what they're doing, each must 
pass a test where he or she is asked to find the track in a few test 
samples. To judge the reliability of each volunteer -- and to provide some 
reward in what for most will be a fruitless search -- the team also plans 
to throw in some ringers with and without tracks.

"We will throw in some calibration images that allow us to measure the 
volunteers' efficiency," Westphal said.

If at least two of the four volunteers viewing each image report a track, 
that image will be fed to 100 more volunteers for verification. If at 
least 20 of these report a track, UC Berkeley undergraduates who are 
expert at spotting dust grain tracks will confirm the identification. 
Eventually, the grain will be extracted for analysis. Discoverers will get 
to name their dust grains.

The dust grains were collected in two phases during the Stardust 
spacecraft's seven-year journey to and from Wild 2 as the spacecraft 
turned its Stardust Interstellar Dust Collector (SIDC) into the 
interstellar dust stream, which courses through the solar system at a 
speed of about 20 kilometers (12 miles) per second. The dust grains will 
have made carrot-shaped trails in the aerogel, which is a novel, 
silicon-based sponge 100 times lighter than water.

In the early morning hours of Jan. 15, 2006, the Stardust payload will 
parachute into Utah's Salt Lake Desert and be airlifted to Houston, where 
teams will open it so as to minimize contamination from other dust. When 
launched in 1999, NASA was unsure how to remove from the aerogel the 
micron-sized cometary grains and the nearly invisible interstellar dust 
grains.

"It's amazing that Stardust flew without anyone having a clue as to how to 
get particles out of the aerogel after it came back," Westphal said. "You 
have to give NASA credit for taking a risk."

During Stardust's quiet journey to a rendezvous with a comet, however, 
Westphal led a team that created tools for extracting both comet grains 
and interstellar dust grains. Working with Chris Keller, formerly at the 
Berkeley Sensor and Actuator Center and now at MEMS Precision Instruments, 
he developed microtweezers and what he calls micro-pickle forks to pull 
comet grains from the aerogel for detailed analysis of their elemental and 
isotopic composition. The abundances and composition within comet grains 
will tell scientists about the conditions in the early solar system.

These same techniques will be used to extract interstellar dust grains, 
but first they have to be found. Based on earlier work with glass 
cosmic-ray detectors on the Mir space station, Westphal developed an 
automated microscope to digitally photograph the entire area of the 
aerogel in patches -- the size of a salt grain -- that can be viewed later 
in search of dust particles. The lengthy but exciting search for dust 
grains will be conducted by Internet volunteers.

Once the grains are identified and analyzed, Westphal hopes the 
information will tell about the internal processes of distant stars such 
as supernovas, flaring red giants or neutron stars that produce 
interstellar dust and also generate the heavy elements like carbon, 
nitrogen and oxygen necessary for life.

The virtual microscope was developed by computer scientist David Anderson, 
director of the SETI at home project, along with physics graduate student 
Joshua Von Korff. Craig and Mendez are now creating a teacher's lesson 
guide that uses the Stardust at home Virtual Microscope to teach students 
about the origins of the solar system. A section of the Stardust at home Web 
site also will be aimed at the general public.

Stardust at home website,

     http://stardustathome.ssl.berkeley.edu/