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Masr Pathfinder Update - 07/08/97
PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Mars Pathfinder Mission Status
July 8, 1997
3 p.m. Pacific Daylight Time
The first in-situ chemical measurements ever obtained of a rock
on Mars - nicknamed Barnacle Bill for its rough, barnacle-like surface -
surprised scientists and raised questions about the duration of volcanic
activity occurring on Mars in its early formation.
Dr. Rudolph Rieder, of the Max Planck Institute for Chemistry,
Germany, and principal investigator on the Alpha Proton X-Ray Spectrometer
(APXS) team, reported that Barnacle Bill, an 8-to-10-inch tall rock near the
Mars Pathfinder lander, was unusually rich in silicon, which is more
characteristic of Earth rocks than Martian rocks. On Earth, volcanic rocks
contain significant amounts of free silica in the form of quartz. The rich
silicon content puts Barnacle Bill in one of the most common categories of
volcanic rocks on Earth, known as "andesites."
"It turns out this rock has some rather peculiar chemical
characteristics, which make it very unlike the other SNC meteorites," said
Dr. Hap McSween, University of Tennessee, who is a participating scientist
on the APXS team. (The SNC meteorites are those found on Earth that are
believed to be of Martian origin.)
"In particular, it has a very high content of silicon or silicon
dioxide (quartz)," McSween said. "It appears that Barnacle Bill falls into a
category called 'andesites,' which are among the most common volcanic rocks
on Earth."
Andesites are mixtures of very fine crystalline and other
minerals that are formed through a process known as differentiation.
Differentiation is the process by which crustal materials deep within a
planet's interior are repeatedly melted and remelted, thereby shaping and
reshaping the surface of the planet. Mars today has very few volcanoes and
no continental plates like those found on Earth to suggest it was internally
active for very long. Barnacle Bill's chemical signature may throw that
theory into question.
Today's weather report was similar to yesterday's: at 3 p.m.
local Mars time, it was about 5 degrees Fahrenheit, pressure was about 6.74
millibars, with very light winds out of the northwest.
"The weather on Mars is pretty boring," said Dr. Jeffrey Barnes, Oregon
State University, who is a member of the atmospheric/meteorological
experiment. "Northern summer in the subtropics on Mars is pretty much the
same from day to day. Fifty or 60 days from now, we'll start to see dramatic
changes with fall."
Atmospheric opacity - or how clear the sky is according to
Pathfinder's atmospheric experiment - showed that Mars is moderately dusty
up to about 40 kilometers (25 miles) above the surface. The dust appears to
be uniformly distributed, and is expected to rise as Mars approaches its
dusty season in the fall, Barnes said. The visibility on Mars was estimated
to be about 32 kilometers (20 miles) or more, roughly equivalent to a
moderately smoggy day in Los Angeles.
The rover's next task later today will be to perform a chemical
analysis of the soil around a large rock named "Yogi." Once the soil
measurements are taken, Sojourner will then back up to the left side of the
rock and begin a chemical analysis using the APXS instrument.
On the fifth day of surface operations since Pathfinder's
historic July 4 landing, all spacecraft and rover systems continue to
operate extremely well. Pathfinder is returning data at an unprecedented
rate of more than 8,500 bits per second and has returned 1,575 images of the
Martian surface to date. A 360- degree, color panorama of the Ares Vallis
landing site is expected to be released within the next few days.
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