Jacques van Oene
May 24th 05, 04:03 PM
Press Release
May 20, 2005
Media Only: Peter Golkin 202-633-2374
Public information: 202-633-1000
Website: http://www.nasm.si.edu/research/ceps/research/mars/mars.cfm
Significant Runoff on Early Mars Identified in River Channels By National
Air and Space Museum Geologists
Mars is now a cold, dry desert, but robotic satellites and rovers have
returned new evidence of a warmer and wetter climate more than 3.5 billion
years ago, when conditions may have been more favorable for life.
Geologists at the Smithsonian National Air and Space Museum's Center for
Earth and Planetary Studies, working with colleagues at the University of
Virginia, have discovered 21 river channels in the dry Martian valleys,
which provide new clues to this ancient climate. The researchers have
determined that Martian rivers were about the same size as their
counterparts on Earth, suggesting similar amounts of runoff from
thunderstorms or rapid snowmelt. The findings will appear in the June issue
of the journal Geology.
Until the discovery of channels, scientists could not determine the amount
of water that had flowed through these valleys. As lead author Ross Irwin,
museum geologist, explained, "We have thought for some time that it likely
rained or snowed on early Mars, but until we found the river channels we had
no idea whether we were dealing with drizzle or storms." Co-authors Robert
Craddock, another National Air and Space Museum geologist, and Alan Howard
of the University of Virginia made a detailed "Case for Rainfall on a Warm,
Wet Early Mars" in a 2002 paper.
Larger, periodic floods carve wider river channels, so by measuring the
width of a channel, geologists can estimate the size of the flood that
carved it. To explain the width of the Martian channels, some watersheds
likely received an inch or more of rain per day during storms, or more than
10 inches of melted snow on particularly warm days. Larger watersheds gave
rise to larger river channels, as they do on Earth. Even using a
conservative method to estimate the amount of water discharged through the
rivers, the Martian rivers still matched their terrestrial counterparts in
terms of the volume of water per second during these ancient episodes of
flow.
Previously, only eight river channels had been found in Martian valleys, two
of these by Irwin and Howard in 2002. The new discoveries were made using
the THEMIS camera on the Mars Odyssey spacecraft that is currently in orbit
around Mars. During the 3.5 billion years since water flowed in these
channels, the valley floors have become partly filled by wind-blown sand and
debris from meteorite impacts, so the channels are exposed along only part
of their floors.
The Martian river channels do not appear to have been active nearly as long
as terrestrial rivers have however. "If it rained this hard every day
throughout the many millions of years that runoff occurred, Mars would be
far more heavily eroded than it is," Irwin said. "It seems more likely that
Mars was wet at times with drier intervals in between." Mars may have always
been a desert, but like the desert in the western United States, water
appears to have flowed abundantly at least part of the time.
The Center for Earth and Planetary Studies is the scientific research unit
within the Collections and Research Department of the Smithsonian
Institution's National Air and Space Museum. The Center's scientists perform
original research and outreach activities on topics covering planetary
science, terrestrial geophysics and the remote sensing of environmental
change.
--
--------------
Jacques :-)
www.spacepatches.info
May 20, 2005
Media Only: Peter Golkin 202-633-2374
Public information: 202-633-1000
Website: http://www.nasm.si.edu/research/ceps/research/mars/mars.cfm
Significant Runoff on Early Mars Identified in River Channels By National
Air and Space Museum Geologists
Mars is now a cold, dry desert, but robotic satellites and rovers have
returned new evidence of a warmer and wetter climate more than 3.5 billion
years ago, when conditions may have been more favorable for life.
Geologists at the Smithsonian National Air and Space Museum's Center for
Earth and Planetary Studies, working with colleagues at the University of
Virginia, have discovered 21 river channels in the dry Martian valleys,
which provide new clues to this ancient climate. The researchers have
determined that Martian rivers were about the same size as their
counterparts on Earth, suggesting similar amounts of runoff from
thunderstorms or rapid snowmelt. The findings will appear in the June issue
of the journal Geology.
Until the discovery of channels, scientists could not determine the amount
of water that had flowed through these valleys. As lead author Ross Irwin,
museum geologist, explained, "We have thought for some time that it likely
rained or snowed on early Mars, but until we found the river channels we had
no idea whether we were dealing with drizzle or storms." Co-authors Robert
Craddock, another National Air and Space Museum geologist, and Alan Howard
of the University of Virginia made a detailed "Case for Rainfall on a Warm,
Wet Early Mars" in a 2002 paper.
Larger, periodic floods carve wider river channels, so by measuring the
width of a channel, geologists can estimate the size of the flood that
carved it. To explain the width of the Martian channels, some watersheds
likely received an inch or more of rain per day during storms, or more than
10 inches of melted snow on particularly warm days. Larger watersheds gave
rise to larger river channels, as they do on Earth. Even using a
conservative method to estimate the amount of water discharged through the
rivers, the Martian rivers still matched their terrestrial counterparts in
terms of the volume of water per second during these ancient episodes of
flow.
Previously, only eight river channels had been found in Martian valleys, two
of these by Irwin and Howard in 2002. The new discoveries were made using
the THEMIS camera on the Mars Odyssey spacecraft that is currently in orbit
around Mars. During the 3.5 billion years since water flowed in these
channels, the valley floors have become partly filled by wind-blown sand and
debris from meteorite impacts, so the channels are exposed along only part
of their floors.
The Martian river channels do not appear to have been active nearly as long
as terrestrial rivers have however. "If it rained this hard every day
throughout the many millions of years that runoff occurred, Mars would be
far more heavily eroded than it is," Irwin said. "It seems more likely that
Mars was wet at times with drier intervals in between." Mars may have always
been a desert, but like the desert in the western United States, water
appears to have flowed abundantly at least part of the time.
The Center for Earth and Planetary Studies is the scientific research unit
within the Collections and Research Department of the Smithsonian
Institution's National Air and Space Museum. The Center's scientists perform
original research and outreach activities on topics covering planetary
science, terrestrial geophysics and the remote sensing of environmental
change.
--
--------------
Jacques :-)
www.spacepatches.info