Bulletin of the Eastbay Astronomical
Society
Founded in 1924 at Chabot Observatory, Oakland, California
Volume 77, Number 2, October 2000
Discovery of Water on Mars
Dr. Jeff Moore
NASA Ames Research
Center
Saturday, 14 October,
2000
General Meeting 7:31 p.m.
Lecture 8:20 p.m.
Chabot Observatory, 4917 Mountain Boulevard, Oakland, California
Nirgal Vallis is an ancient
valley thought to have been carved, in part, by running water
far in the martian past. Today the valley is, like the rest of
Mars, quite dry. However, some of the high resolution Mars Global
Surveyor images reveal small gullies on the walls of this valley
system. As shown here, channels nearly one kilometer long run
down the south-facing slope of the Nirgal Vallis wall. Each narrow
channel starts at about the same position below the top of the
valley wall, indicating that there is a layer along which a liquid—most
likely, water—has percolated until it reached the cliff,
then ran down hill to form the channels and the fan-shaped aprons
at the bottom of the slope. Since some of the apron deposits seem
to cover the dunes on the floor of the valley, the channels and
aprons must have formed more recently than the dunes. Because
neither the dunes nor the aprons and channels have impact craters
on them, these features are all geologically young, meaning a
few million years at most, a few days or weeks at least. Credit:
NASA/JPL/Malin Space Science Systems
Just three months ago, one of the most startling announcements
of the space age was made: evidence for very recent liquid water
flowing on Mars. This amazing discovery was the result of recent
Mars Global Surveyor images. Gullies were seen on the sides of
Martian canyons and craters. On Earth, such landforms occur when
water suddenly flows across desert-like terrain, leaving a distinctive
pattern. What is particularly exciting is that the gullies and
washes below them appear to be very recent. Most of them have
no cratering and at least one flows over a sand dune area. Sand
dunes on Mars are thought to be constantly changing from windstorms
whipping the planet. This suggests that these formations are recent,
perhaps very recent (a few months or years ago). If this is so,
then liquid water may exist on Mars right now!
These gullies are found in over 120 locations on slopes that face
away from the Sun between 30 and 70 degrees latitude in both the
Northern and Southern Martian hemispheres. It is thought that
the colder temperature on these slopes allows ice to seal in the
subsurface water at depths ranging from about 300 to 1300 feet
(100 to 400 meters) below the surface.
It is still possible that other, more exotic explanations may
explain these formations. The leading candidate is clathrates,
a fizzing, bubbling mixture of gas and debris that flows like
water.
If these formations are from recent liquid water flow, then the
implications are enormous. It is now thought that Mars had rivers,
lakes, rain and perhaps even an ocean or two on its surface for
about one and a half billion years. This is important because,
on the Earth, life got started within the first one hundred million
years of the existence of such conditions. This implies that life
may well have gotten started on Mars during its wet and warm period.
As Mars began to freeze, Martian life could have retreated to
these subsurface pools where the Martian life would be protected
from the intense ultraviolet radiation on the surface. There may
be life in those hypothesized pools right now. And the life would
have had about four billion years to evolve! Furthermore, we now
know that Mars and Earth exchange substantial amounts of material.
It is possible that one planet could have biologically “contaminated”
the other. In other words, we could be Martians!
There is no better person to discuss these exciting results and
the upcoming missions to Mars than Dr. Jeff Moore, a trained geologist
who is intimately involved with many of the aspects of the Mars
program.
Dr. Jeffrey M. Moore is a Research Scientist with the SETI Institute,
and is based at NASA Ames Research Center in Mountain View. Dr.
Moore has both a history and a geophysics degree from the University
of Oklahoma. He got his Masters and Ph.D. in Geology from Arizona
State University. He has spoken several times to EAS, most recently
in March, 2000, about the discoveries of the Galileo Mission.
In January, 1999, he told us about the popular culture of observations
of Mars.
For more information about this exciting discovery check http://www.space.com/scienceastronomy/solarsystem/mars_science_findings_000622
.html.
To view the fascinating images from Mars global surveyor, go to
http://mars.jpl.nasa.gov/mgs/msss/camera/images/june2000/index.html.
DINNER WITH THE SPEAKER
5:27 pm, Saturday, 14 October 2000
BLUE NILE RESTAURANT
2525 Telegraph Avenue, Berkeley (510) 540-6777
Please call Betty Neall at 510/533-2394 by Friday, 13 October
to confirm your place. Note the time has been advanced to allow
everyone to be able to get to the meeting promptly at 7:31 pm.
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