New images from NASA?s Mars Global Surveyor spacecraft show signs of recent climate change dating back about 100,000 years instead of millions or billions, including ?megafloods? that may have triggered climate changes, extensive terrain that closely mimics permafrost areas on Earth, lake beds, and gullies that have drained water and debris on the Martian surface within the past several million years.
Probably the most important evidence are the tell-tale signs of very recent glaciers. The presence of glaciers means that Mars once was a lot warmer and that there was much more water on the Martian surface.
John Mustard and other geologists at Brown University in Providence, Rhode Island, have identified and mapped the terrain of Mars, which looks like cemented ice, suggesting there are shallow ice reserves below the surface.
High-resolution images from Surveyor show the terrain is breaking down, indicating climate change and perhaps modern Martian ice ages. ?The layer is so young it is evidence of climate change very recently and perhaps operating the same way as the Earth?s ice age,? Mustard says.
Knowledge of climate change on Mars is very crude and on a billion-year time scale. The new findings, published in the science journal Nature, suggest a potentially active climate cycle on the planet. ?It puts it into a much more recent time frame and it puts it into a periodic notion that this is happening on a regular basis,? says Mustard.
Piles of crater-topped debris snapped by Surveyor that were caused by an explosion of water through volcanic lava flows at the planet?s equator are the best evidence yet for recent liquid water on Mars. Under a model devised by the University of Arizona and University of Hawaii researchers, these ?rootless cones? formed after volcanic eruptions melted frozen water near the surface of Mars 10 million years ago, which is practically present time from the geological point of view. The melting caused floods that carved channels and seeped into the ground.
The Martian cones range from house-sized to small stadium-sized, and resemble similar features in Iceland which form when surface lava interacts explosively with near-surface groundwater. ?We think lava flows have advanced over the wet ground causing steam explosions that built these rootless cones,? says Laszlo Keszthelyi, a senior research associate at Arizona's Lunar and Planetary Laboratory. ?It means Mars is not dead geologically. Volcanic eruptions and water floods are something ongoing into the current geologic era.? His findings have been published in Geophysical Research Letters.
Some scientists think the cones were caused by carbon dioxide, but Keszthelyi is confident that they are the result of liquid water exploding through lava. ?The area is just too warm to have CO2 stick around,? he says. Temperatures and surface pressures at the equator provide the right recipe for liquid water.
Scientists have known for a long time that there is water frozen into Mars? polar caps. But that water is locked in a vapor-ice cycle and never liquefies. So signs of liquid water, especially in areas that are distant from Mars? poles, excites researchers who looking for conditions suitable for life. In fact, there could be liquid water at Mars right now, says Keszthelyi's colleague Alfred S. McEwen.
There are three scenarios that scientists argue for the source of the shallow water ice that exploded to bust through the lava and form the cones on Mars. It could be leftover from the planet?s formation, it could have condensed from vapor in the atmosphere, or it could be the result of surface flooding.
New evidence from the Mars Global Surveyor probe has also sparked speculation that the first human explorers might discover fossils of ancient life forms. The watery environment has big implications for the existence of past or present life on Mars, according to Professor Victor Baker, head of the Department of Hydrology and Water Resources at the University of Arizona in Tucson.
The first human explorers on Mars might even discover fossils of ancient life forms. ?Early Mars provided an arguably better habitat for the inception and incubation of early life than did early Earth,? says Baker.
Previously, scientists believed no water had flowed on the surface of Mars for around four billion years. But the Surveyor evidence suggests that considerable amounts of water shaped Martian land features within the past 10 million years. Scientists think internal heat periodically triggers short-term warmer and wetter conditions on Mars. Such conditions may be conducive to life, Professor Baker told the journal Nature.
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