[meteorite-list] Stardust Leaves Scientists to Ponder

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon, 12 Feb 2007 09:41:01 -0800 (PST)
Message-ID: <200702121741.JAA17608_at_zagami.jpl.nasa.gov>

http://www.sltrib.com/news/ci_5210029

Stardust leaves scientists to ponder

A year after the capsule fell into the Utah desert, much remains a mystery

By Greg Lavine
The Salt Lake Tribune
February 12, 2007

NASA's Scott Sanford was one of the first scientists to reach the small
Stardust mission capsule sitting on the west desert floor a little more
than a year ago.
    Now he and other scientists around the globe are gleaning
information about the origins of the solar system from the microscopic
comet bits recovered from the capsule.
    Under the chilly pre-dawn skies of Jan. 15, 2006, Sanford and other
researchers watched the intact capsule land and realized their
seven-year wait for pieces of a comet was finally over. The space
agency's Stardust spacecraft dropped off a sample return cannister,
which landed around 3 a.m., containing debris snagged from a comet.
    "We're picking up this thing that has travelled 3 billion miles to
get to us," Sanford, of NASA's Ames Research Center in California,
recalled thinking once he saw the intact capsule.
    The landing marked the end of the mission in one sense, but the
start of an ongoing journey for scientists. Pieces of Comet Wild 2 are
already illuminating details about our early solar system.
    Comet Wild 2 spent much of its life lurking at the frigid edges of
the solar system, far from the intense heat of the sun. Researchers
believed Wild 2 would serve as a frozen package of matter preserving
material from the earliest days of the solar system, said Tom Duxbury,
Stardust's project manager.
    Like many NASA missions, the findings yielded surprises.
    "We found that 10 percent of the minerals were formed under high
heat" meaning the material was formed near the sun, he said.
    Because most of the comet's contents show no signs of exposure to
heat, Wild 2 did spend most of its existence in the coldest reaches of
the solar system. But that doesn't explain the heated particles.
    "If they came from the inner part of the solar system, how did they
get cycled out to the outer edge of the solar system," asked Duxbury of
the heat-formed material.
    An explanation for this movement would need to be accounted for in
creating models for how the solar system formed. In the earliest days,
there was a solar nebula - a swirling, disk-shaped cloud of dust and gas
with an early version of the sun at the center.
    "This implies there was a lot of mixing going on in the early solar
nebula," Sanford said of the early Stardust results.
    It is possible there may have been circulation patterns within the
disk that moved material away from the developing sun. There is also the
idea that some material was shot out of the inner part of the disk only
to later land in the outer edge.
    "The early solar system was not a nice, sedate little
merry-go-round," Sanford said.
    Don Brownlee, a University of Washington researcher who was a
principal investigator of Stardust, said the findings will force
scientists to rethink the early solar system. There had been theories
about materials being mixed, but no evidence to support it until this
mission.
    "This was a major surprise," he said.
    Another science oddity related to the name of the mission:
Researchers anticipated Wild 2 to be chock-full of material dating to
before the formation of the solar system.
    "There was an expectation that most of the material of the comet
would be what is called stardust," which is material formed around other
suns, Brownlee said.
    How much stardust has Stardust found? Not much.
    Frank Stadermann, a researcher from Washington University of St.
Louis, specializes in searching for stardust particles. The early goings
were a bit dicey, but the mission name was not entirely a bust.
    "Finally, we found one stardust particle," he said, adding there is
plenty of material left to search.
    The search for more stardust, as well as other particles, will
continue for years. Researchers will develop new techniques to examine
the tiny particles.
    There is also another part of the Stardust mission that could
continue in the near future.
    Duxbury said the spacecraft is still working and has plenty of fuel.
NASA is considering a mission to fly the craft toward the Tempel 1
comet, which was made famous in 2005 when the space agency fired a
missile-like projectile at it to see what would happen.
    For now, the Stardust craft is orbiting the sun in a
hibernation-like state. While it waits for new orders, scientists will
continue to reap the benefits of the craft's original mission.
Received on Mon 12 Feb 2007 12:41:01 PM PST