[meteorite-list] HiRISE Camera Returns New View of Dark Pit on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 29 Aug 2007 13:27:04 -0700 (PDT)
Message-ID: <200708292027.NAA10464_at_zagami.jpl.nasa.gov>

http://cms-test.opi.arizona.edu/node/15715

HiRISE CAMERA RETURNS NEW VIEW OF DARK PIT ON MARS --
AND ADDS 930 MORE IMAGES TO NASA SPACE MISSION ARCHIVE
(From Lori Stiles, University Communications, 520-626-4402)

- Aug. 29, 2007

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Contact information, Web link information at the end
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The High Resolution Imaging Experiment (HiRISE) has confirmed that a dark
pit seen on Mars in an earlier HiRISE image really is a vertical shaft that
cuts through lava flow on the flank of the Arsia Mons volcano. Such pits
form on similar volcanoes in Hawaii and are called "pit craters."

The HiRISE camera, orbiting the red planet on NASA's Mars Reconnaissance
Orbiter, is the most powerful camera ever to orbit another planet. It is
operated at The University of Arizona in Tucson. HiRISE Principal
Investigator Alfred McEwen of the UA's Lunar and Planetary Laboratory and
his team released the new image of the dark pit on Arsia Mons and several
other stunning images today on the HiRISE Web site,
http://hirise.lpl.arizona.edu. New HiRISE images are released on the site
every Wednesday.

The UA-based HiRISE team also released another 930 images to the Planetary
Data System (PDS), the U.S. space agency's mission data archive, today.
These images, taken between May and July 2007, include a view of what at
first glance looks deceptively like a mesa set in Swiss cheese terrain. But
it's a case of "trompe l'oeil," an eye trick -- the feature is a crater.

The "Swiss cheese" terrain is carbon dioxide ice that "sublimates," or thaws
from a solid directly into gas, during the summer, which it currently is at
this south polar region of Mars. Carbon dioxide sublimating on steep slopes
changes the shape of pits and mesas from year to year. The large depression
in this image might be an impact crater, McEwen said, although it's hard to
be sure because there's no raised rim or ejecta. Impact craters on the ice
cap are modified as the ice-rich terrain "relaxes" over time and as they are
resurfaced by the annual deposition and sublimation of frost and ice.

Another image shows a very recent "rayed" dark impact crater among older
pocks in the lighter, dust-covered surface. An extremely recent impact,
perhaps only a few years or decades ago, created the dark spot with radial
and concentric patterns in this HiRISE image. The small central crater is
only about 18 meters wide (60 feet), but it formed a dark spot 700 meters
wide (two-fifths mile) with rays of secondary craters reaching as far as 3.7
kilometers (more than two miles) from the central crater, McEwen said.
Secondary craters are rocks ejected from the central crater. "This region of
Mars is covered by dust, and the impact event must have removed or disturbed
the dust to create the dark markings," McEwen said.

All HiRISE images released to the PDS can be viewed from the HiRISE site.
There also is a direct link to the full directory listing at
http://hirise-pds.lpl.arizona.edu/PDS.

Today's release adds another 1.8 terabytes to the PDS. The project turned
over its first 1,200 HiRISE images to PDS last May. The PDS now holds a
total 3.5 terabytes of HiRISE data, one of the largest single datasets
returned from a spacecraft and archived in NASA's space mission library.

Internet users can explore the images with the user-friendly "IAS Viewer"
software that can be downloaded from the HiRISE Web site. IAS-Viewer
technology allows users to quickly explore part of an enormous HiRISE image
because the software transmits only as much data as needed to render any
selected part of the image on a computer screen. The tool delivers a
high-resolution view of the selected part of the image regardless of slow or
limited Internet connections.

The HiRISE camera takes images of 3.5-mile wide (6 kilometer) swaths as the
orbiter flies at about 7,800 mph between 155 and 196 miles (250 to 316
kilometers) above Mars' surface. HiRISE science imaging began in November
2006 and will continue at least through November 2008.

Information about the Mars Reconnaissance Orbiter spacecraft is online at
http://www.nasa.gov/mro. The mission is managed by NASA's Jet Propulsion
Laboratory, a division of the California Institute of Technology, Pasadena,
for the NASA Science Mission Directorate, Washington, D.C. Lockheed Martin
Space Systems, Denver, is the prime contractor and built the spacecraft.
Ball Aerospace and Technologies Corp., Boulder, Colo., built the HiRISE
camera operated by The University of Arizona.

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Contact information
Alfred S. McEwen 520-621-4573 mcewen at pirl.lpl.arizona.edu
Eric Eliason 520-626-0564 eeliason at pirl.lpl.arizona.edu

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HiRISE Web site
 http://hirise.lpl.arizona.edu
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Link to this story, photos on the UA News.org Website
http://cms-test.opi.arizona.edu/node/15715
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Received on Wed 29 Aug 2007 04:27:04 PM PDT