[meteorite-list] EPOXI Spacecraft Hurtles Toward Active Comet Hartley 2

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 15 Oct 2010 15:44:39 -0700 (PDT)
Message-ID: <201010152244.o9FMidk0010325_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/science-news/science-at-nasa/2010/15oct_epoxi/

NASA Spacecraft Hurtles Toward Active Comet Hartley 2
NASA Science News

October 15, 2010: NASA's Deep Impact/EPOXI spacecraft is hurtling
toward Comet Hartley 2 for a breathtaking 435-mile flyby on Nov. 4th.
Mission scientists say all systems are go for a close encounter with one
of the smallest yet most active comets they've seen.

"There are billions of comets in the solar system, but this will be only
the fifth time a spacecraft has flown close enough to one to snap
pictures of its nucleus," says Lori Feaga of the EPOXI science team.
"This one should put on quite a show!"

Cometary orbits tend to be highly elongated; they travel far from the
sun and then swing much closer. At encounter time, Hartley 2 will be
nearing the sun and warming up after its cold, deep space sojourn. The
ices in its nucleus will be vaporizing furiously - spitting dust and
spouting gaseous jets.

"Hartley 2's nucleus is small, less than a mile in diameter," says
Feaga. "But its surface offgasses at a higher rate than nuclei we've
seen before. We expect more jets and outbursts from this one."

EPOXI will swoop down into the comet's bright coma - the sparkling aura
of debris, illuminated by the sun - shrouding the nucleus. The
spacecraft's cameras, taking high-resolution (7 meters per pixel at
closest approach) pictures all the while, will reveal this new world in
all its fizzy glory.

"We hope to see features of the comet's scarred face: craters,
fractures, vents," says Sebastien Besse of the science team. "We may
even be able to tell which features are spewing jets!"

The spacecraft's instruments are already trained on their speeding target.

"We're still pretty far out, so we don't yet see a nucleus," explains
Besse. "But our daily observations with the spectrometer and cameras are
already helping us identify the species and amounts of gases in the coma
and learn how they evolve over time as we approach."

The aim of the mission is to gather details about what the nucleus is
made of and compare it to other comets. Because comets spend much of
their time far from the sun, the cold preserves their composition - and
that composition tells a great story.

"Comets are left-overs from the 'construction' of our solar system,"
explains Besse. "When the planets formed out of the 'stuff' in the solar
nebula spinning around the sun, comets weren't drawn in."

Researchers study these pristine specimens of the primal solar system to
learn something about how it formed, and how it birthed a life-bearing
planet like Earth.

"These flybys help us figure out what happened 4 1/2 billion years ago,"
says Feaga. "So far we've only seen four nucleii. We need to study more
comets to learn how they differ and how they are the same. This visit
will help, especially since Hartley 2 is in many ways unlike the others
we've seen."

EPOXI will provide not only a birds-eye view of a new world but the best
extended view of a comet in history.

"This spacecraft is built for close encounters. Its instruments and our
planned observations are optimized for this kind of mission. When, as
Deep Impact, it flew by Tempel 1, it turned its instruments away from
the nucleus to protect them from debris blasted up by the impactor. This
time we won't turn away."

The EPOXI team will be waiting at NASA's Jet Propulsion Laboratory.

"We'll start diving into the data as soon as we receive it," says Feaga.
"We'll work round the clock, on our toes the whole time, waiting for the
next thing to come down."

Sounds like it could be intense.

"It's already intense," says Besse. "We're getting more and more data,
but at encounter we'll be flooded!"

And that will be only the beginning.


Author: Dauna Coulter
Editor: Dr. Tony Phillips
Credit: Science at NASA

More Information

EPOXI <http://epoxi.umd.edu/> -- home page

Sebastien Besse's EPOXI blog <http://epoxi.umd.edu/6outreach/daily.shtml>

On July 4, 2005, NASA's Deep Impact spacecraft's impactor blasted out a
crater in the nucleus of Comet Tempel 1. Deep Impact's prime mission was
to punch a hole in Tempel 1 and look inside, giving researchers their
first glimpse of a comet's internal structure. EPOXI is Deep Impact
"recycled." The EPOXI mission uses the already "in flight" Deep Impact
flyby spacecraft. The name EPOXI comes from the spacecraft's two
extended missions: the extrasolar planet observations, called Extrasolar
Planet Observations and Characterization (EPOCh), already completed, and
the impending flyby of comet Hartley 2, called the Deep Impact Extended
Investigation (DIXI). For the first time scientists will be able to
directly compare two different comets with the same cameras, the same
science team, and same processes. This eliminates possible systematic
variations like calibration difference between instruments. "We'll know
we're comparing apples to apples," says Feaga.

Before Comet Hartley 2,spacecraft have given us close up looks at four
cometary nuclei: Halley, Borrelly, Tempel 1, and Wild 2.
Received on Fri 15 Oct 2010 06:44:39 PM PDT