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Mars Channels May Have Been Carved by Ice
By
Senior Science Writer
posted: 09:44 am ET
17 January 2001
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mars_ice_010117 Comparing sonar maps and satellite images of Antarctica with images of Mars, a geologist has bolstered a long-held belief that some Martian channels may have been carved by ice, rather than catastrophic floods of liquid water.Terrestrial ice streams, which snake slowly beneath the frozen surface of Antarctica, were long invisible to normal satellite imaging until radar imaging made them visible in the late 1990s. And now, ship-based sonar missions map the area where these ice flows merged with the surrounding seafloor during the last Ice Age, carving telltale patterns. The Antarctic ice stream patterns and the Martian channels are of similar size -- hundreds of miles (kilometers) long and tens of miles wide, says Baerbel Lucchitta of the U.S. Geological Survey in Flagstaff, Arizona. They also both exhibit similar grooves, ridges and fluted formations. Importantly, the Martian features are found along the edges of an area in the northern plains of Mars -- a region thought to have once been an ocean. Because the Martian features strikingly resemble places on Earth where ice flows met the Antarctic Ocean during the last Ice Age, the new research lends further evidence to the idea that Mars once had oceans. "I think that ice shaped the outflow channels in places, but not necessarily everywhere," Lucchitta told SPACE.com. "There probably were [liquid water] floods, but perhaps not as large as people think, because ice rather than floods could have formed some of the mega-features we see in the channels." Jack Farmer, director of the astrobiology program at Arizona State University, said the possibility of a northern ocean on Mars, as the new research implies, is important to those who would search for signs of life on the Red Planet. A Martian ocean implies large sedimentary deposits -- great hunting grounds for fossils or microbes."A northern ocean requires a lot more water than we normally think about for Mars and with potentially large subsurface aquifers that could still harbor extant subterranean life forms," said Farmer, who was not involved in the new work. Ice and mud Lucchitta said the suspected ice flows could not account for all of the channels seen on Mars. There were probably mudflows on Mars, too. But on a cold Mars, any water or mud would have iced over. The resulting ice jams could have been temporary and might have recurred, she said, and "may have been sufficient to sculpt depressions or preexisting channels and valleys in places." The study, funded by NASA, is discussed in the Feb. 1 issue of Geophysical Research Letters. Among other locales, Lucchitta studied the ancient seafloor carvings left behind by Antarctica's Rutford ice stream, which diverged around a higher, more stable area of ice when it flowed into the Ronne Ice Shelf. She compared this to a similar flow in the Ares Vallis region of Mars, where there is evidence that something has flowed around an island. Flow lines that are similar to those found in Antarctica hint at a hypothetical Martian ocean. Lucchitta expects that Ares Vallis was filled by ice, mud or some other material that had the characteristics of flowing ice. It appears to have entered an ice covered body of water, such as an ocean. She believes some of the ice may still be there, covered by dust. The researcher also noted that some of the channels on Mars appear to swoop uphill near their outflows. This resembles similar processes and features on Earth where ice at the base of glaciers and ice streams sometimes flows uphill, driven by a rising subsurface. Water, of course, cannot generally flow uphill, except when pushed for short distances. The parallels between ice streams on Mars and Earth get complex in the details, Lucchitta said.In Antarctica, ice streams flow from vast sheets of ice. On Mars, however, they may be spawned by fluids, possibly including water, erupting from below the surface and then freezing. Other recent findings have supported the idea that water might have flowed to the Martian surface in the recent past, and possibly still does so.Real answers won't come until upcoming missions explore the surface of Mars, Farmer said. "The Earth has had many intervals of global-scale glaciation, separated by warmer intervals," Farmer said. "Was the same true for Mars, or has the planet always been locked in a deep freeze? We simply don't know for sure. Obviously, we need to understand that history of climate and water to understand the potential for life, whether in the past or today." Click here for more news and information about Mars.
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