[meteorite-list] The Mysterious Molasses Markings of Pluto

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 16 Apr 2010 13:33:52 -0700 (PDT)
Message-ID: <201004162033.o3GKXqpQ019886_at_zagami.jpl.nasa.gov>

http://science.nasa.gov/science-news/science-at-nasa/2010/14apr_molasses/

The Mysterious Molasses Markings of Pluto
NASA Science News

April 16, 2010: Lonely Pluto floats in the darkness at the edge of our
solar system. It's so far away even the Hubble Space Telescope has
trouble making out the details. Nevertheless, Pluto is so interesting,
even fuzzy images of the dwarf planet are compelling.

A team of researchers led by Marc Buie of the Southwest Research
Institute recently released the best Hubble images to date:

The data reveal an icy molasses-colored world with a surprising amount
of activity. Buie compared Hubble images taken in 1994 vs. 2003 and
discovered that Pluto's northern hemisphere has brightened while the
southern hemisphere has dimmed. Ground-based observations suggest that
Pluto's atmosphere doubled in mass during approximately the same time
period. And no one is certain what's causing the molasses-colored
splotches on Pluto's surface.

"It's baffling," says dwarf planet expert Mike Brown of Caltech. "For
now, we can only guess. Although these images are the best we have to
date, they just aren't clear enough to answer all the questions they
raise."

For instance, what's happening to Pluto's atmosphere?

Pluto can get so cold, researchers believe, that its atmosphere can
actually freeze and fall to the ground. If Earth's atmosphere did that,
it would make a layer 30 feet thick, but Pluto has less to work with.
When it's on the ground, Pluto's entire blanket of air is no more than a
frosty film of nitrogen and methane.

"Until the mid-1980s, Pluto's northern hemisphere was tilted away from
the sun for over 100 years, accumulating a substantial amount of frost,"
says Buie. "Now the northern hemisphere is coming into sunlight and
appears, as shown in the Hubble images, to have been growing brighter."

The atmosphere might also be changing in response to Pluto's highly
eccentric orbit. During the late 1980s, Pluto approached as close to the
sun as it ever gets (about 2 1/2 billion miles) and gradually started
warming. Now the temperature on Pluto is up to a balmy -385 degrees
Fahrenheit! Surface frosts exposed to such "warmth" may be
subliming - that is, changing back into a gas.

"Pluto, right now, has the best atmosphere it's had in our lifetime,"
says Brown.

And about that molasses...

Researchers think these dark areas may be primordial organic matter.

"We know there's methane on Pluto," says Brown. "Here's what we think
happens: Sunlight hits the methane and breaks it apart into its chemical
components -- hydrocarbons. Over millions of years this process makes a
dark reddish-brown oil or tar like substance that sticks to the ground.
These darker areas spread larger as they absorb more sunlight and cause
additional frost to sublimate."

"Now, Pluto is headed away from the sun again," says Brown. "It will
gradually get colder and colder and its atmosphere will refreeze to its
surface. In fact, that should have already started happening, but
apparently it has not. It's a mystery."

NASA's New Horizons probe is en route to investigate. The spacecraft
left Earth in January 2006 and has been racing toward Pluto for an
encounter in July 2015, hopefully before the atmosphere refreezes.

"New Horizons will map the entire sunlit portion of Pluto," says Buie.
"And as it swings closer, it will get very detailed images, maybe as
good as 50-100 meter resolution."

"This will allow us to explore some of the interesting areas we've
pinpointed," he continues. "For example, the recent Hubble images reveal
a very bright spot - brighter than anything else on Pluto - near the
equator. And just to the left of that bright spot is some of the darkest
terrain on Pluto's surface. We want to examine the area where these
bright and dark areas are touching and figure out what's causing the
differences. This is a good target because it includes every kind of
terrain Pluto has to offer."

"We know there are surprises waiting for us on Pluto," says Brown.

Author: Dauna Coulter
Editor: Dr. Tony Phillips
Credit: Science at NASA
Received on Fri 16 Apr 2010 04:33:52 PM PDT