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Pathfinder Images Show Martian Sunset
By DIANE AINSWORTH
Recent images taken by taken by the Imager for Mars
Pathfinder (IMP) instrument aboard the Carl Sagan Memorial
Station show the Martian sunrise and sunset, with water ice
clouds floating through the atmosphere.
The collection of photographs included one portion of the
super panorama view looking to the north-northeast from the
Pathfinder lander. The super panorama of the landing site, which
is being constructed from high resolution color images taken by
the Imager for Mars Pathfinder (IMP) instrument, will be
comprised of about 3,000 images when it is completed in about
seven weeks, said Pathfinder Project Scientist Dr. Matthew
Golombek. This mammoth color and stereo data set, which is now
about 65 percent finished, will be used to derive high quality
topographic maps of the Martian surface and detailed shapes of
rocks and other surface features. Scientists will also be able to
examine subtle chemical, mineralogical and textural variations in
rocks and soils from this panorama.
Temperatures on Mars remained in roughly the same range they
have been in since the start of the mission. The low on Aug. 27
was minus 75 degrees Celsius (-103 degrees Fahrenheit) and the
high was minus 10 degrees Celsius (14 degrees Fahrenheit). The
highest pressure measurements seen yet on Mars were recorded Aug.
26 (Sol 52) at 6.8 millibars, said Dr. Tim Schofield, atmospheric
structure/meteorology package team leader at JPL. In addition to
temperature and pressure measurements, Pathfinder has observed a
total of 12 dust devils, small swirls of dust kicked up by winds
blowing down through the canyons in the Ares Vallis landing zone.
Scientists are finding that Martian temperatures are cooler
at higher altitudes (about 80 kilometers or 50 miles) than on the
ground. They think that ice clouds forming about 10 kilometers to
15 kilometers (six to nine miles) above the surface are
responsible for this cooling trend higher in the atmosphere. The
clouds are thought to be made of very small ice particles, about
one-tenth the size of Martian dust or one-thousandth the
thickness of a human hair.
Dr. Mark Lemmon, a member of the lander camera imaging team
at the University of Arizona, noted color variations in some of
the sunset pictures. The blue color is not caused by clouds of
water ice but by Martian dust in the atmosphere, Lemmon said. The
dust absorbs blue light, giving the sky its red color, but it
also scatters some of the blue light into areas that looked very
blue around the Sun. The blues only show up near sunrise and
sunset, when the light has to pass through the largest amount of
Sojourner, which remains in excellent health, began
exploring the Rock Garden Aug. 28 after spending about a week en
route to the region. The Rock Garden is an assemblage of several
large boulders and many smaller rocks near the lander. After
conducting a chemical analysis of the rock nicknamed Shark, the
rover moved toward another rock called Half Dome, but climbed too
high up on the rock and automatically shut itself off.
On Aug. 28, the rover team instructed the rover to back down
the rock and reposition the alpha proton X-ray spectrometer
against the side of Half Dome.
Chemical analyses of all of the rocks studied so far
indicate that at least two types of rocks are present in the
Pathfinder landing zone: those with high levels of silicon and
those with high levels of sulfur, reported Dr. Tom Economou, co-
investigator of the alpha proton X-ray spectrometer team at the
University of Chicago.
Soil mechanics experiments using the rover's wheels and
cleats to dig below the surface have revealed different layers of
material, Howard Eisen, principal investigator on the soil
mechanics technology experiment at JPL, pointed out. Soil
surfaces differ near the lander, where the soil contains a
mixture of pebbles, fine-grained sand and clods, from regions a
bit farther out. There, the surface is covered with a bright
drift material, Eisen said. Using the rover's cleats to dig below
the surface, scientists have discovered that cloddy material was
present underneath the drift.
After traveling a total of about 80 meters (263 feet) around
the landing site, Sojourner will continue to explore the Rock
Garden for the next several days, taking as many chemical
analyses as possible of the large boulders in the vicinity. After
these rocks have been studied, the rover will head back to the
ramp on which it exited the lander and study a dust sample that
has been accumulating on a magnet, Golombek said. This study may
provide new information about magnetic properties that might be
present in the Martian soil. Longer range plans for the rover may
take it much farther away from the lander, so that it may peer
over the rim of what appears to be a shallow riverbed, and
photograph a region that cannot be seen by the lander.
Images and comprehensive updates on Pathfinder science
results are available on the Internet at
http://mpfwww.jpl.nasa.gov or via JPL's Web site at
http://www.jpl. nasa.gov/marsnews/. Daily audio updates are also
available by calling (800) 391-6654.