ASU Instrument Keeping an Eye on Growing Mars Dust Storm
Scientists at Arizona State University’s Mars Space Flight Facility are using the Thermal Emission Imaging System (THEMIS) on NASA’s Mars Odyssey orbiter to monitor a new dust storm that has erupted on the Red Planet.
The dust storm began in mid-March 2009, in the large Southern
Hemisphere impact basin named Hellas. It has since grown as it spread
northward in a patchy fashion. How large the storm will become is
unknown, but previous storms have grown to envelop the whole planet
for weeks at a time.
“This storm is coming at a time in the Martian year — around the
planet’s closest approach to the Sun — when dust storms are common,”
says Philip Christensen, of the Mars Space Flight Facility on the
Tempe campus. Christensen, a Regents’ Professor of geological sciences
in the School of Earth and Space Exploration, is the designer and
principal investigator for the THEMIS camera.
“But so far,” he says, “this storm has not reached the severity of the
big dust storm of 2001, or even the more modest one in 2007.”
Mars’ closest approach to the sun comes April 21, and summer begins in
the planet’s southern hemisphere a month later. Both effects combine
to produce the atmospheric heating that drives the dust activity.
Dust in the Eyes
Dust storms affect operations for all five spacecraft working at Mars.
The fleet includes two NASA rovers on the ground (Spirit and
Opportunity), plus three orbiters, two of which belong to NASA (Mars
Odyssey and Mars Reconnaissance Orbiter) and one from the European
Space Agency (Mars Express).
Caption: Greens, yellows, and reds map the growing density of dust in the
Martian atmosphere, as seen during the first week of April 2009 by ASU’s Thermal Emission Imaging Spectrometer on NASA’s Mars Odyssey orbiter. The storm originated in the Hellas impact basin, the red patch at lower right.
“If the dust causes a lot of obscuration, we lose the ability to image
the ground,” explains Christensen. “In big dust storms, the rover
teams are strongly affected as dust in the air reduces sunlight which
provides power for driving and science operations. And when the dust
finally settles out, it coats the solar panels, diminishing their
capability.”
“We’ve noticed increasing opacity over the last several days,” says
Steve Ruff, of the Mars Space Flight Facility. “This has produced
roughly a 20 percent drop in power for Spirit.” Ruff is in charge of
day-to-day operations for the Miniature Thermal Emission
Spectrometers, a mineral-scouting instrument each rover carries.
In the 2007 storm, dust blocked more than 99 percent of the sunlight
for both rovers.
“When dust kicks up,” Ruff says, “it hurts.”
THEMIS (http://themis.asu.edu/about) is a sophisticated camera thattakes images in 5 visual bands and 10 heat-sensing (infrared) ones. At infrared wavelengths, the smallest details THEMIS can see on the surface are 330 feet (100 meters) wide.
Current and older dust map images are available at:
http://themis.asu.edu/dustmaps. Click on each maps for a higher-resolution version. Please credit NASA/JPL/Arizona State University.
Latest dust map image link:
http://themis.asu.edu/dustmaps/detail/thmdust_32372-32450.html
