In the wee
hours of our solar system, massive explosions on the sun might have sent
free-floating gases whizzing at such high speeds that they embedded into tiny
rock particles. These "rocklets" were then transported beyond Neptune and incorporated into a comet, researchers said today.
New
research reveals surprisingly large amounts of the noble gases helium and neon
in samples taken from comet Wild 2 (pronounced "Vilt 2"). The
results, detailed in the Jan. 4 issue of the journal Science, suggest
the gases came from a region very near the young sun, say the researchers.
Noble gases
are a group of six elements that don't react with other elements. Since they
are stable, noble gases are great "tracers" of chemicals from various
parts of the solar system.
Preliminary
examination of the comet samples, returned to Earth by NASA's Stardust mission in
2006, had revealed so-called igneous rock particles that only form under
high-temperature conditions. On Earth, igneous rocks form when magma cools and
solidifies, either after erupting from volcanoes or tucked beneath layers of
earth.
So
astronomers had previously concluded the particles that later got incorporated
into Wild 2 formed very close
to the sun, probably within the first million years of our solar system's
history.
The new
research "further characterizes the environment that they were in at the
time they were formed," said study researcher Robert Pepin of the School of Physics and Astronomy at the University of Minnesota.
Odd-shaped
blobs comprising a mix of dust grains and frozen gases, comets
may be the oldest, most primitive bodies in the solar system. They hold the
earliest record of material from the nebula that formed the sun and planets.
While the
grains in Wild 2 spent most of their lives in the frigid, distant reaches of
the solar system, they were likely captured in "rocklets" that formed
very close to the sun. Until recently, Wild 2 circled the sun in an orbit
between Jupiter and Uranus, but in 1974 a close encounter with Jupiter sent the
comet into an orbit that brings it closer to the sun.
What
embedded the atoms of helium and neon into these rocklets? The researchers say
intense radiation
near the sun. "Not only was the environment hot, but it appeared to
have been characterized by a lot of radiation which probably came from immense,
early, magnetically driven solar flares very close to the sun," Pepin told
SPACE.com.
The
radiation, he explained, apparently accelerated particles of gases to such high
speeds they embedded themselves into the little grains.
Even though
the comet particles formed in the sun's neighborhood, the chemical makeup of
the embedded noble gases looked nothing like solar material. Instead, the ratio
of different forms of the helium and neon resembled that found in certain
primitive meteorites, according to the researchers.
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