Tucson - July 23, 2001
Scientists have known for decades that Mars, at least in its ancient past, has had a considerable amount of water.
But when Mars Global Surveyor began mapping the Red Planet in sharp detail early in 1999, it disclosed startling evidence that water has shaped martian landforms within the past 10 million years.
The discovery challenges the prevailing view that Mars' surface has remained extremely cold and dry -- much as it is today -- for the past 3.9 billion years.
It confirms the idea that internal heat periodically triggers short-term warmer and wetter conditions -- conditions conducive to life -- in the global martian hydrological cycle, University of Arizona Regents' Professor Victor R. Baker says in a review article, "Water and the martian landscape," published by Nature July 12. Baker is head of the UA department of hydrology and water resources.
Mars is cold, dry and quiet for long periods of the hydrological cycle, periods spanning hundreds of millions of years, Baker says. It becomes actively warmer and wetter during brief episodes that last perhaps thousands to tens of thousands of years.
He summarizes evidence of permafrost and ground ice, surface water and glacial ice seen first in early 1970s images from Mariner 9 flybys and in later 1970s images from the Viking missions. New results from Mars Orbital Camera (MOC) and Mars Orbiter Laser Altimeter (MOLA) are not only consistent with the view that water shaped the geology of Mars -- they say it happened very recently.
New spacecraft images have revealed:
"We don't know the answer to that yet -- that's very speculative, " Baker said. "But if it's true, it would have major implications for sending people to Mars, because it may mean that water is more available than otherwise thought."
UA planetary scientist William V. Boynton's Gamma Ray Spectrometer (GRS) heading to Mars on the Mars Odyssey spacecraft will begin its 917 Earth-day mapping mission in December 2001 or January 2002. The GRS will map the amounts of all the elements over the entire surface of Mars. Hydrogen would signal the presence of water or ice buried as deep as a meter in Mars' dust.
Other high-resolution spectrometers, cameras and robotic devices now in the planning stages also will search for martian water, Baker said. When scientists have learned as much as possible from these remote sensing instruments, one idea is to send a number of small, simple and inexpensive surface penetrators to be dropped at several places on the planet to test for the presence of water.
For now, however, new images from the Mars Orbital Camera and Mars Orbital Laser Altimeter further confirm that "brief episodes of water-related activity, including glaciation, punctuate the geological history of Mars." Baker wrote in Nature
Evidence for recent martian glaciers is among the most important and controversial, he said.
"If there are glaciers, then Mars is very different than many people have described it," he said. "Glaciers aren't ice cubes, sitting there to waste away. In order to have glaciers, you have to have precipitation. Water has to move through the atmosphere, and it precipitates and makes the ice grow."
And glaciers don't form in the coldest environments, he added. Glaciers form where there is cold and moisture. "But for there to be moisture, it can't be supercold," he noted. "The atmosphere has to be warm enough to evaporate water and move it through the air. The presence of glaciers means that Mars once was a lot warmer, and that there was much more water on the martian surface. The presence of glaciers suggests that there must have been standing bodies of water as well. "
How could it happen?
Confronted by Viking images of young fluvial and glacial features on Mars -- stream valleys that apparently were formed by precipitation and glacial features over large areas of the planet, Baker, Robert G. Strom and other UA scientists in 1991 theorized what has become known as the "MEGAOUTFLO" model.
Basically, the hypothesis says that over the long term, water and volatiles remain frozen as ground ice and ground water in the subsurface because Mars is so distant from the sun and extremely cold. The perennially frozen permafrost acts like a cap on a soda bottle. And just as gas and water in a capped soda bottle explode when heated, sporadic bursts of internal planetary heat trigger the dramatic release of gas and water locked under the permafrost.
They theorize that so much water is released in such episodes that a temporary ocean forms repeatedly over the northern hemisphere. Massive martian volcanism near the northern hemisphere's Thasis Bulge has -- and may again -- trigger an ocean.
Carbon dioxide released to the atmosphere promotes the warming greenhouse effect so that liquid water is stable near the martian surface. Mars lacks a soil layer like Earth's, so when it rains, water filters underground rather than collecting on the surface. Local valleys and other observed martian features form when near-surface water gushes up from below. But when it rains, water removes carbon dioxide from the atmosphere, and Mars chills to the point that permafrost reforms, plunging the planet into another dry, frigid long-lasting epoch.
The extensive hydrosphere implied by Mars' water-generated geology "may exist only as ground ice in the thick permafrost zone and as underlying groundwater," Baker wrote in Nature. "Yet, this is the type of environment in which the extremophile progenitors of Earth's biosphere probably evolved. Indeed, early Mars provided an arguably better habitat for the inception and incubation of early life than did early Earth."
And if that's the case, he added, there could be fossils.
Subscribe To SpaceDaily Express
Tectonics Not Oceans Shaped Ancient Ridges
Tucson - April 4, 2001
What scientists suspect might be ancient ocean shorelines on the northern plains of Mars is actually a network of tectonic ridges related to dramatic martian volcanism, a University of Arizona planetary sciences graduate student and a collaborating post-doctoral researcher at the Massachusetts Institute of Technology report in the April 5 issue of Nature.
Watery Tales From Texas
Cameron Park - May 4, 2001
Some theorists at this year's Lunar and Planetary Sciece Conference again reiterated their belief that there is evidence that substantial amounts of liquid water flowed on at least some parts of Mars not just in its earliest times, but occasionally in much more recent geological times -- perhaps less than a hundred million years ago.
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2016 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|