(See description below.)
MARS LANDSCAPE AT MARS PATHFINDER LANDING SITE
Mars Pathfinder Mission Status
July 15, 1997
The Mars Pathfinder flight team today reported on
a very successful night of data transmission, receiving an
unprecedented 90 megabits of data on the chemical makeup of a
boulder nicknamed Yogi, atmospheric measurements and nearly all
remaining portions of a 360-degree color panorama image of the
landing site.
Last night's downlink sessions contained detailed information on
the chemistry of Yogi taken by the rover after a second attempt
to position its alpha proton X-ray spectrometer against the rock.
The new data also included measurements of the aerosol content of
the Martian atmosphere, which was used in parallel with new
Hubble Space Telescope images of Mars to characterize changes in
regional and global weather patterns in the last three weeks.
Recent incidents in which the Pathfinder lander's computer reset
itself were discussed by Glenn Reeves, flight software team
leader. According to Reeves, computer resets have occurred a
total of four times during the mission -- on July 5, 10, 11 and
14. The flight team has attempted to avoid future resets by
instructing the computer to handle one activity at a time --
"serializing" activities -- rather than juggling a
number of activities at once.
The team continues to troubleshoot the problem by testing all of
the sequences leading up to reset in JPL's Mars Pathfinder
testbed; considering changes in the flight software that would
allow for immediate recovery if the flight computer were to reset
itself; and modifying operational activities to minimize data
loss if a reset should occur again. "In a sense, the reset
itself is not harmful because it brings us back into a safe
state," said Reeves. "But it does cause a disruption of
the operational activities."
Among the science highlights, the Pathfinder mineralogy team
presented new information about Barnacle Bill, a very roughly
textured rock, and Yogi, a much larger boulder nearby, which was
successfully measured last night.
Yogi, low in quartz content, appears to be more primitive than
Barnacle Bill, "having not gone through the cooking that
Barnacle Bill and other andesites have gone through," said
Dr. James Greenwood, University of Tennessee, a member of the
mineralogy science team. Although these observations are very
preliminary, Yogi appeared to be more like the common basalts
found on Earth. The next rock to be studied is "Scooby
Doo," followed by others, including "Half Dome,"
"Wedge," "Shark" and "Flat Top,"
all located in a different region of the landing site. Some are
near the lander petal on which Sojourner flew to Mars.
Observations from the Earth-orbiting Hubble Space Telescope
revealed a lot of surface-atmospheric transport activity. A dust
storm detected in Vallis Marineris just prior to Pathfinder's
landing, for instance, had all but vanished within two weeks
according to new Hubble images, noted Dr. Steven Lee, University
of Colorado, a Hubble investigator. Some of the dust from that
regional storm had diffused to the Pathfinder landing site, which
was consistent with recent Pathfinder atmospheric opacity
measurements.
In observations taken between May 18 and July 11, the amount of
dust near the Pathfinder landing site had nearly tripled.
"There's obviously a lot of very rapid transport going on
here, with some of the dust diffusing toward the landing
area," Lee said. "This is consistent with Pathfinder
observations on the surface."
The increase in atmospheric dust appears to be diminishing the
amount of cloudiness, Lee added. Clouds observed near the
southern polar hood had begun to decrease in the most recent
Hubble images as the dust diffused throughout the southern
hemisphere. The Hubble team estimated that these clouds were
relatively low, hovering around 15 to 16 kilometers (9 to 10
miles) above the surface, because the tips of some Martian
volcanoes could be seen peeking through the cloud tops.
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