“If you have visited one asteroid, you have
not visited them all.” — LINDA ELKINS-TANTON
Probe visits a planetary also-ran
NEWS BRIEFS
body is what’s known as an enstatite
chondrite — a rare form of asteroid that
makes up around 2 percent of the meteor-
ites that have fallen to Earth. “It’s pretty
uncommon,” says planetary scientist and
study author Pierre Vernazza of the Euro-
pean Southern Observatory. “Our under-
standing is that this kind of meteorite is
the starting composition of the terrestrial
planets, from Mercury to the Earth.”
A density that high suggests that the
asteroid is not a rubble pile, or collection
of fragments produced by violent colli-
sions. Rather, the rocky body has prob-
ably maintained its primordial state,
and might have a differentiated interior,
with a metallic core, mantle and surface
that never melted, says Elkins-Tanton.
Lutetia’s ancient and complex surface — marked with landslides, enormous
craters, faults and fractures — supports
the finding that the asteroid is primitive and undisturbed, and suggests that
it formed within the solar system’s first
3 million years, she says.
But the question of where Lutetia
formed is still open. A team of scientists,
unclear, the team reports.
Asteroid 21 Lutetia isn’t just another
pebble in a big pile of space rocks. Scientists now think it is a leftover planetary seed, booted into the main belt by
the planetary bullies growing around it.
Lutetia and its asteroid cousins are
thought to be relics from the early solar
system, rocky fossils that have recorded
a history of the solar system’s early days
in their pits and fractures. In July 2010,
the European Space Agency’s Rosetta
spacecraft flew within 3,200 kilometers
of Lutetia, peered at the asteroid and
attempted to read its stony story.
Using data gathered by Rosetta, three
reports appearing in the Oct. 28 Science
describe Lutetia’s surprising composition and terrain.
“If you have visited one asteroid, you
have not visited them all,” says Linda
Elkins-Tanton of the Carnegie Insti-
tution for Science in Washington, D.C.
“We can still learn some amazing new
things about planetesimals, primitive
materials, solar system dynamics and
[asteroid] composition.”
Scientists estimate that Lutetia is
121 kilometers by 101 kilometers by
75 kilometers. Data suggest that the
Space splash
Scientists spying on stars have
seen what they think is evidence
for aquatic collisions of cosmic
proportions. Water-bearing comets seem to be slamming into an
exoplanet orbiting the star Eta
Corvi, a mere 60 light-years away
and easily visible in the sky. Eta
Corvi is surrounded by an icy disk
with chunks that are probably the
fragments of former comets. An
international group of astronomers concludes that the disk
around the star was produced by
several smaller comets — or one
big one — colliding with the yet-to-be-discovered planet. The team
reports the observation in a paper
to appear in the Astrophysical
Journal. — Nadia Drake
The asteroid Lutetia appears to be
a remnant planetary seed that was
kicked out of the inner solar neighborhood and landed in the main
asteroid belt.
Kinky interstellar molecules
Unidenti;ed infrared emissions in
interstellar space are not caused
by polycyclic aromatic hydrocarbons, new research indicates. To
explain the mysterious emissions,
scientists have been searching
for years for the highly organized
organic molecules, best known for
their role in atmospheric pollution
on Earth. Now, Sun Kwok and Yong
Zhang of the University of Hong
Kong suggest that the emissions
are the signatures of other, disorganized organic compounds. The
team reached this conclusion by
examining data stored in the Infrared Space Observatory’s archive.
The kinky compounds are similar
to materials found in meteorites,
suggesting that the solar system
might have inherited its organics from interstellar space, the
researchers report online October
26 in Nature. —Nadia Drake
