Mars Sunset Clip Tells Dusty Tale

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

Guy Webster (818) 354-5011
Jet Propulsion Laboratory, Pasadena, Calif.

Donald Savage (202) 358-1547
NASA Headquarters, Washington, D.C.

NEWS RELEASE: 2004-070 February 26, 2004

Mars Sunset Clip Tells Dusty Tale

Dust gradually obscures the Sun during a blue-sky martian sunset seen
in a sequence of newly processed frames from NASA's Mars Exploration
Rover Opportunity.

"It's inspirational and beautiful, but there's good science in there,
too," said Dr. Jim Bell of Cornell University, Ithaca, N.Y., lead
scientist for the panoramic cameras on Opportunity and its twin,
Spirit.

The amount of dust indicated by Opportunity's observations of the Sun
is about twice as much as NASA's Mars Pathfinder lander saw in 1997
from another site on Mars.

The sunset clip uses several of the more than 11,000 raw images that
have been received so far from the 18 cameras on the two Mars
Exploration Rovers and publicly posted at

http://marsrovers.jpl.nasa.gov .

During a briefing today at NASA's
Jet Propulsion Laboratory, Pasadena, Calif., Bell showed some pictures
that combine information from multiple raw frames.

A patch of ground about half the area of a coffee table, imaged with
the range of filters available on Opportunity's panoramic camera, has
soil particles with a wide assortment of hues -- "more spectral color
diversity than we've seen in almost any other data set on Mars," Bell
said.

Opportunity is partway through several days of detailed observations
and composition measurements at a portion of the rock outcrop in the
crater where it landed last month. It used its rock abrasion tool this
week for the first time, exposing a fresh rock surface for
examination. That surface will be studied with its alpha particle
X-ray spectrometer for identifying chemical elements and with its
Moessbauer spectrometer for identifying iron-bearing minerals. With
that rock-grinding session, all the tools have now been used on both
rovers.

Dr. Ray Arvidson of Washington University, St. Louis, deputy principal
investigator for the rovers' science work, predicted that in two weeks
or so, Opportunity will finish observations in its landing-site crater
and be ready to move out to the surrounding flatland. At about that
same time, Spirit may reach the rim of a larger crater nicknamed
"Bonneville" and send back pictures of what's inside. "We'll both be
at the rims of craters," he said of the two rovers' science teams,
"one thinking about going in and the other thinking about going out
onto the plain."

Not counting occasional backup moves, Spirit has driven 171 meters
(561 feet) from its lander. It has about half that distance still to
go before reaching the crater rim. The terrain ahead looks different
than what's behind, however. "It's rockier, but we're after rocks,"
Arvidson said.

Spirit can traverse the rockier type of ground in front of it, said
Spirit Mission Manager Jennifer Harris of JPL. As it approached the
edge of a small depression in the ground earlier this week, the rover
identified the slope as a potential hazard, and "did the right thing"
by stopping and seeking an alternate route, she said.

However, engineers are also planning to transmit new software to both
rovers in a few weeks to improve onboard navigation capabilities. "We
want to be more robust for the terrain we're seeing," Trosper said.
The software revisions will also allow engineers to turn off a heater
in Opportunity's arm, which has been wasting some power by going on
during cold hours even when not needed.

As it heads toward "Bonneville" to look for older rocks from beneath
the region's current surface layer, Spirit is stopping frequently to
examine soil and rocks along the way. Observations with its microscope
at one wavy patch of windblown soil allowed scientists to study how
martian winds affect the landscape. Coarser grains are concentrated
on the crests, with finer grains more dominant in the troughs, a
characteristic of "ripples" rather than of dunes, which are shaped by
stronger winds. "This gives us a better understanding of the current
erosion process due to winds on Mars," said Shane Thompson, a science
team collaborator from Arizona State University, Tempe.

The rovers' main task is to explore their landing sites for evidence
in the rocks and soil about whether the sites' past environments were
ever watery and possibly suitable for sustaining life.

JPL, a division of the California Institute of Technology in Pasadena,
manages the Mars Exploration Rover project for NASA's Office of Space
Science, Washington, D.C. Images and additional information about the
project are available from JPL at

http://marsrovers.jpl.nasa.gov

and from Cornell University at

http://athena.cornell.edu/ .

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