NASA Study Shows Water Could Create Gullies on Mars

http://www.nasa.gov/centers/ames/res...sguillies.html

John Bluck
NASA Ames Research Center, Moffett Field, Calif.
Phone: 650/604-5026
E-mail:

NASA Study Shows Water Could Create Gullies on Mars
August 24, 2005

NASA scientists say liquid water formed recent gullies on Mars.

A NASA-led team will present its Mars gully findings at the American
Astronomical Society's Division for Planetary Sciences annual meeting
in
Cambridge, England, Sept. 5, 2005.

"The gullies may be sites of near-surface water on present-day Mars and
should be considered as prime astrobiological target sites for future
exploration," ventured National Research Council scientist Jennifer
Heldmann, principal author of the study who works at NASA Ames Research
Center in California's Silicon Valley.

"The gully sites may also be of prime importance for human exploration
of Mars because they may represent locations of relatively near surface
liquid water, which can be accessed by crews drilling on the red
planet," she added.

"If liquid water pops out onto Mars' surface, it can create short
gullies about 550-yards (500-meters) long," Heldmann said. "We used a
computer to simulate the flow of liquid water within gully channels,"
Heldmann explained.

"Our model indicates that these fluvially-carved gullies were formed in
the low temperature and low pressure conditions of present-day Mars by
the action of relatively pure liquid water," said Heldmann.

The science team found that the maximum length of gullies simulated in
the computer models were comparable to the martian gullies studied. "We
find that the short length of the gully features implies they did form
under conditions similar to those on present-day Mars, with
simultaneous
freezing and rapid evaporation of nearly pure liquid water," Heldmann
said.

In addition, images taken by the Mars Global Surveyor spacecraft show
'geologically young' small-scale features on the red planet that
resemble terrestrial water-carved gullies, according to scientists.

"The young geologic age of these gullies is often thought to be a
paradox, because liquid water is unstable at the martian surface,"
Heldmann said. At present martian air pressure and temperature, water
will boil and freeze at very rapid rates, the scientists reported.

Team scientists noticed that images of some of Mars' gullies show that
they taper off into very small debris fields ? or no debris fields at
all - suggesting that water rushing through the gullies rapidly froze
and/or evaporated.

"In the martian case, fluid well above the boiling point (which is a
very low temperature at Mars' low atmospheric pressure and air
temperature) is suddenly exposed to the atmosphere," said Heldmann.
"The
difference between the vapor and ambient pressures relative to the
ambient pressure is large, and flash boiling can occur, leading to a
violent loss of fluid."

Scientists believe that ice probably would not accumulate in the
gullies, because of the rapid evaporation of water and relatively high
flow velocities, but in some cases, some ice could be carried
downstream. The researchers studied computer simulations of both
scenarios.

"We tested our model using known flow parameters and environmental
conditions of perennial saline springs in the Mars analog environment
of
the Canadian High Arctic," Heldmann noted.

In addition to Heldmann, Chris McKay, also of NASA Ames; Brian Toon,
Michael Mellon and John Pitlick, of the University of Colorado,
Boulder;
Wayne Pollard, of McGill University, Montreal, Canada; and Dale
Andersen, of the SETI Institute, Mountain View, Calif., are study
co-authors.

Images related to this news release may be found on the Web at:

http://www.nasa.gov/centers/ames/mul...rsgullies.html
..