[meteorite-list] What is Creating Gullies on Vesta?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 6 Dec 2012 13:46:27 -0800 (PST)
Message-ID: <201212062146.qB6LkRSO015094_at_zagami.jpl.nasa.gov>

http://www.jpl.nasa.gov/news/news.php?release=2012-389

What is Creating Gullies on Vesta?
Jet Propulsion Laboratory
December 06, 2012

In a preliminary analysis of images from NASA's Dawn mission, scientists
have spotted intriguing gullies that sculpt the walls of geologically
young craters on the giant asteroid Vesta. Led by Jennifer Scully, a
Dawn team member at the University of California, Los Angeles, these
scientists have found narrow channels of two types in images from Dawn's
framing camera - some that look like straight chutes and others that
carve more sinuous trails and end in lobe-shaped deposits. The mystery,
however, is what is creating them?

The presentation on gullies is one of several that Dawn team members are
making at this year's American Geophysical Union conference in San
Francisco. Other topics include craters on Vesta, the giant asteroid's
mineralogy, and the distinctive dark and bright materials found on the
surface.

"The straight gullies we see on Vesta are textbook examples of flows of
dry material, like sand, that we've seen on Earth's moon and we expected
to see on Vesta," said Scully, who presented in-progress findings on
these gullies today. "But these sinuous gullies are an exciting,
unexpected find that we are still trying to understand."

The sinuous gullies are longer, narrower, and curvier than the short,
wide, straight gullies. They tend to start from V-shaped, collapsed
regions described as "alcoves" and merge with other gullies. Scientists
think different processes formed the two types of gullies and have been
looking at images of Earth, Mars and other small bodies for clues.

"On Earth, similar features - seen at places like Meteor Crater in
Arizona -- are carved by liquid water," said Christopher Russell, Dawn's
principal investigator, also based at UCLA. "On Mars, there is still a
debate about what has caused them. We need to analyze the Vesta gullies
very carefully before definitively specifying their source."

Indeed, scientists have suggested various explanations for gullies on
Mars since fresh-looking gullies were discovered in images from NASA's
Mars Global Surveyor in 2000. Some of the proposed Martian mechanisms
involve water, some carbon dioxide, and some neither. One study in 2010
suggested that carbon-dioxide frost was causing fresh flows of sand on
the Red Planet.

JPL manages the Dawn mission for NASA's Science Mission Directorate in
Washington. Dawn is a project of the directorate's Discovery Program,
managed by NASA's Marshall Space Flight Center in Huntsville, Ala. The
University of California at Los Angeles (UCLA) is responsible for
overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va.,
designed and built the spacecraft. The German Aerospace Center, the Max
Planck Institute for Solar System Research, the Italian Space Agency and
the Italian National Astrophysical Institute are international partners
on the mission team. The California Institute of Technology in Pasadena
manages JPL for NASA. For more information about Dawn, visit:
http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov .

Jia-Rui C. Cook/D.C. Agle 818-354-0850/393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
jccook at jpl.nasa.gov / agle at jpl.nasa.gov

2012-389
Received on Thu 06 Dec 2012 04:46:27 PM PST