Jun 26 2008
From The Space Library
A team of scientists reported in the journal Nature that they had gathered new evidence to support the theory that Mars’s Borealis Basin is a large impact crater. After NASA’s Viking spacecraft had captured the first clear images of the Martian surface in the 1970s, scientists had puzzled over the dichotomy of the planet: the roughly cratered southern highlands have an altitude 2.5 to 5 miles (4.02 to 8.05 kilometers) higher than the smooth plains of the northern lowlands. One theory that scientists had advanced to explain this dichotomy was that the impact of a foreign object had created the lowlands of the Borealis Basin. However, many in the scientific community had doubted this theory because the images from the 1970s suggested that the basin did not have the typical shape of an impact crater. In the article in Nature, NASA’s MRO and NASA’s Mars Global Surveyor teams reported that they had gathered new topographical and gravitational data, showing that the basin has an elliptical shape consistent with that of impact craters. Moreover, two other studies published in the same Nature issue had used computer models to demonstrate that a meteor might conceivably have created the Borealis Basin. Scientists estimated that an object 1,250 miles (2,011.68 kilometers) wide, traveling at a speed of approximately 20,000 miles (32,186.88 kilometers) per hour, could have formed the crater when it crashed into Mars. If this theory proved correct, the Borealis Basin would be the largest known impact crater in the solar system.
NASA, “NASA Spacecraft Reveal Largest Crater in Solar System,” news release 08-159, 25 June 2008, http://www.nasa.gov/home/hqnews/2008/jun/HQ_08159_Mars_crater.html (accessed 21 April 2011); Kenneth Chang, “Astronomers Explain Mars’s Lopsided Shape,” New York Times, 26 June 2008; see also Jeffrey C. Andrews-Hanna, Mary T. Zuber, and W. Bruce Banerdt, “The Borealis Basin and the Origin of the Martian Crustal Dichotomy,” Nature 453, no. 7199 (26 June 2008): 1212–1215.
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