Ancient asteroid may have created biggest known landslide on Mars

January 7th, 2009 - 2:16 pm ICT by ANI  

National Geographic

Washington, Jan 7 (ANI): Scientists have said that an asteroid may have triggered a landslide on Mars billions of years ago, which is the size of the entire United States, and the largest known anywhere.

The finding could help solve the origin mystery of Marss Arabia Terra region, a vast, midlevel plateau between the planets smooth northern lowlands and rugged southern highlands.

According to a report in National Geographic News, estimated at about 1,000 miles (1,600 kilometers) wide, the giant asteroid is believed to have struck Marss northern hemisphere billions of years ago.

The cataclysm is thought to have given the planet its topographical split personality smooth in the north, but bumpy down south.

The impact site became the smooth, low-lying Borealis Basin, about 6,000 miles (10,000 kilometers) across. The southern part of the planet became highlandsin places several miles higher than the basin.

The border of the two regions is sharply defined, except for the Arabia Terra zone. This odd middle ground is neither highlands nor basin.

Until recently, the reason for the region had been unknown.

Arabia Terra is a relic of the giant asteroid impact, according to geophysicist Jeff Andrews-Hanna, of the Colorado School of Mines.

This unusual midland was created when a U.S.-size portion of the highlands broke free and slid 180 miles (300 kilometers) northward, down into the southern rim of the Borealis Basin, Andrews-Hanna said.

In other words, three of Marss largest geographic features the Borealis Basin, the highlands, and Arabia Terra were formed virtually instantaneously, in a single catastrophic collision, the geophysicist said

According to Andrews-Hanna, the first clue that Arabia Terra was formed via landslide is that the relatively flat region has steep slopes at both its northern and southern edges, which is like a giant step.

Similar features occur in other large impact craters, many of which have bulls-eye patternsconcentric circles or ellipses of steep ridges separated by gently sloping plateaus.

The similarity of Arabia Terra to these other craters indicates that it too might have been created by an impact.

Another clue is that, at Arabia Terra, the inner rim of the Borealis Basin doesnt line up with its inner rim elsewhere on the planet.

Instead, the rim juts northward by about 300 kilometers, as if a landslide had smudged the clean break seen in areas to the west and east. (ANI)

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