[meteorite-list] NASA Mars Weathercam Helps Find Big New Crater (MRO)
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 22 May 2014 11:19:09 -0700 (PDT)
NASA Mars Weathercam Helps Find Big New Crater
Jet Propulsion Laboratory
May 22, 2014
Researchers have discovered on the Red Planet the largest fresh
meteor-impact crater ever firmly documented with before-and-after
images. The images were captured by NASA's Mars Reconnaissance Orbiter.
The crater spans half the length of a football field and first appeared
in March 2012. The impact that created it likely was preceded by an
explosion in the Martian sky caused by intense friction between an
incoming asteroid and the planet's atmosphere. This series of events can
be likened to the meteor blast that shattered windows in Chelyabinsk,
Russia, last year. The air burst and ground impact darkened an area of
the Martian surface about 5 miles (8 kilometers) across.
The darkened spot appears in images taken by the orbiter's
weather-monitoring camera, the Mars Color Imager (MARCI). Images of the
site from MARCI and from the two telescopic cameras on Mars
Reconnaissance Orbiter are at:
Since the orbiter began its systematic observation of Mars in 2006,
scientist Bruce Cantor has examined MARCI's daily global coverage,
looking for evidence of dust storms and other observable weather events
in the images. Cantor is this camera's deputy principal investigator at
Malin Space Science Systems, the San Diego company that built and
operates MARCI and the orbiter's telescopic Context Camera (CTX).
Through his careful review of the images, he helps operators of NASA's
solar-powered Mars rover, Opportunity, plan for weather events that may
diminish the rover's energy. He also posts weekly Mars weather reports.
About two months ago, Cantor noticed an inconspicuous dark dot near the
equator in one of the images.
"It wasn't what I was looking for," Cantor said. "I was doing my usual
weather monitoring and something caught my eye. It looked usual, with
rays emanating from a central spot."
He began examining earlier images, skipping back a month or more at a
time. The images revealed that the dark spot was present a year ago, but
not five years ago. He homed in further, checking images from about 40
different dates, and pinned down the date the impact event occurred; the
spot was not there up through March 27, 2012, and then appeared before
the daily imaging on March 28, 2012.
Once the dark spot was verified as new, it was targeted last month by
CTX and the orbiter's sharpest-sighted camera, the High Resolution
Imaging Science Experiment (HiRISE). Of the approximately 400 fresh
crater-causing impacts on Mars that have been documented with
before-and-after images, this is the only one discovered using a MARCI
image, rather than an image from a higher-resolution camera.
CTX has imaged nearly the entire surface of Mars at least once during
the orbiter's seven-plus years of observations. It had photographed the
site of this newly-discovered crater in January 2012, prior to the
impact. Two craters appear in the April 2014 CTX image that were not
present in the earlier one, confirming the dark spot revealed by MARCI
is related to a new impact crater.
HiRISE reveals more than a dozen smaller craters near the two larger
ones seen in the CTX image, possibly created by chunks of the exploding
asteroid or secondary impacts of material ejected from the main craters
during impact. It also reveals many landslides that darkened slopes in
the 5-mile surrounding area. A second HiRISE image in May 2014 added
"The biggest crater is unusual, quite shallow compared to other fresh
craters we have observed," said HiRISE Principal Investigator Alfred
McEwen of the University of Arizona, Tucson.
The largest crater is slightly elongated and spans 159 by 143 feet (48.5
by 43.5 meters).
McEwen estimates the impact object measured about 10 to 18 feet (3 to 5
meters) long, which is less than a third the estimated length of the
asteroid that hit Earth's atmosphere near Chelyabinsk. Because Mars has
much less atmosphere than Earth, space rocks of comparable size are more
likely to penetrate to the surface of Mars and cause larger craters.
"Studies of fresh impact craters on Mars yield valuable information
about impact rates and about subsurface material exposed by the
excavations," said Leslie Tamppari, deputy project scientist for the
Mars Reconnaissance Orbiter mission at NASA's Jet Propulsion Laboratory
in Pasadena, California. "The combination of HiRISE and CTX has found
and examined many of them, and now MARCI's daily coverage has given
great precision about when a significant impact occurred."
NASA is developing concepts for its asteroid initiative to redirect a
near-Earth asteroid -- possibly about the size of the rock that hit Mars
on March 27 or 28, 2012 -- but much closer to Earth's distance from the
sun. The project would involve a solar-powered spacecraft capturing a
small asteroid or removing a piece of a larger asteroid, and redirecting
it into a stable orbit around Earth's moon.
Astronauts will travel to the asteroid aboard NASA's Orion spacecraft,
launched on the agency's Space Launch System rocket, to rendezvous with
the captured asteroid. Once there, they would collect samples to return
to Earth for study. This experience in human spaceflight beyond
low-Earth orbit will help NASA test new systems and capabilities needed
to send astronauts to Mars in the 2030s.
Malin Space Science Systems, San Diego, built and operates MARCI and
CTX. The University of Arizona, Tucson, operates HiRISE, which was built
by Ball Aerospace & Technologies Corp. of Boulder, Colorado. JPL, a
division of the California Institute of Technology, Pasadena, manages
the Mars Reconnaissance Orbiter Project for NASA's Science Mission
Directorate, Washington. Lockheed Martin Space Systems, Denver, built
the spacecraft and collaborates with JPL to operate it.
For more information about the Mars Reconnaissance Orbiter and its
Jet Propulsion Laboratory, Pasadena, Calif.
guy.webster at jpl.nasa.gov
dwayne.c.brown at nasa.gov
Received on Thu 22 May 2014 02:19:09 PM PDT