From: LARRY KLAES (ljk4@msn.com)
Date: Fri Dec 06 2002 - 04:54:54 PST
----- Original Message -----
From: Ron Baalke
Sent: Thursday, December 05, 2002 6:13 PM
To: ljk4@msn.com
Subject: Exposed Water Ice Discovered Near the South Pole of Mars
http://www.usgs.gov/public/press/public_affairs/press_releases/pr1693m.html
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News Release Address
Office of Communication
U.S. Department of the Interior 119 National Center
U.S. Geological Survey Reston, VA 20192
Release Contact Phone Fax
December 5, 2002 Stephannie Hanna 415-905-1007 (until 12/10)
Timothy Titus 928-555-7201
Catherine Puckett 797-442-1329
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Exposed Water Ice Discovered Near the South Pole of Mars
Surface water in the form of ice exposed near the edge of Mars's southern
perennial polar cap has been discovered for the first time, according to
U.S. Geological Survey (USGS) research released today in the journal
Science. There is evidence that the surface water ice in this region may be
widespread - from a half-mile to six miles around the entire southern polar
ice cap.
USGS space scientist Timothy Titus and his colleagues Hugh Kieffer of USGS
and Philip Christensen of Arizona State University noted that although it
has long been known that water ice should be present in the southern polar
region of Mars, until recently little evidence for water ice had been found.
Previously, surface water ice had been documented on the northern polar cap
of Mars, but this is the first time exposed water ice has been documented on
the southern polar cap of the solar system's fourth planet.
Titus and his colleagues used images from the Mars Odyssey Thermal Emission
Imaging System (THEMIS) and temperature data from the Mars Global Surveyor
Thermal Emission Spectrometer (TES) to confirm the presence of water ice at
the surface of the southern polar cap.
In addition, the Mars Odyssey Gamma Ray Spectrometer (GRS) observations
showed that there is quite a bit of water ice buried beneath the surface in
the southern polar region, but because GRS could not "identify" exposed
water ice at the surface when the ice is only a few miles wide, scientists
were not sure if exposed water ice existed at the surface of the southern
polar regions of Mars.
Enter THEMIS and TES - with their high-resolution images and sensitive
temperature-monitoring data, THEMIS was "able" to tell the scientists where
to look for possible water areas. "When we first saw the images from THEMIS,
we noticed that areas that were dark were not all the same temperature,
which suggested that the areas were composed of different stuff, perhaps
even water ice," Titus said.
The scientists then looked at TES data that overlapped the THEMIS images and
found that in one area, called Unit I, the water ice warmed up slowly in the
summer after the dry ice covering had sublimated away. (Under martian
conditions water ice does not melt, it goes directly from solid to a gaseous
state, a process called sublimation.) The temperature remained under about
-90 degrees Fahrenheit, the hottest martian ice gets and about the
temperature of the northern summer ice cap on Mars, which is composed of
dirty water ice (ice mixed with dirt and dust).
"On the southern polar ice caps, the differences between daytime and
nighttime temperatures were small, which also suggested to us that the
"stuff" might be water ice," Titus said.
Titus and his colleagues also examined unit S, located adjacent to unit I.
It showed a different trend in temperatures than unit I. In unit S, as
temperatures warmed early in the Mars summer, the dry ice covering changed
from solid ice to gas much earlier than in unit I, and in a matter of a few
days or so. Suddenly, said Titus, daytime temperatures jumped and the
nighttime temperature stayed the same, which told us that as the dry ice
sublimated, probably what was left behind was a 2-7 mm layer of dust over
ice.
"This suggests that the top layer changed from dirty water ice to dry dust,"
Titus said. "The cool nighttime temperatures are what one would expect from
having a layer of water ice underneath the thin layer of dust."
Titus and his colleagues are excited about the implications of these
findings. "In some ways, this water ice may just be the 'tip' of the
iceberg," Titus said. "The speculation is that there may be a whole mass of
water ice underneath the southern polar cap."
Determining the abundance and distribution of surface and near-surface water
ice is fundamental for both understanding the water cycle of Mars and for
the future exploration of Mars, Titus noted in the paper. Water ice, at or
near the surface, is available for surface interactions and exchange with
the atmosphere, causing, for example, atmospheric changes such as water
vapor and water ice clouds.
In addition, water ice that is in the top few inches of soil will most
likely be accessible to future robotic probes and, ultimately, human
exploration.
For more information on this and other thermal observations of the Mars
polar region, please visit http://www.mars-ice.org (will be updated on Dec.
6).
The USGS serves the Nation by providing reliable scientific information to
describe and understand the Earth; minimize the loss of life and property
from natural disasters; manage water, biological, energy and mineral
resources; and enhance and protect our quality of life.
### USGS ###
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