Oddly shaped Mars crater a cosmic puzzle

PARIS, Aug. 27 (UPI) -- An elongated crater on Mars is a mystery, say European scientists scrambling for an explanation of its odd shape.

Named Orcus Patera, the enigmatic elliptical depression lies near Mars's equator, in the eastern hemisphere of the planet. Located between the volcanoes Elysium Mons and Olympus Mons, how it was formed remains a mystery, a European Space Agency release said Friday.

The term 'patera' is used for deep, complex or irregularly shaped volcanic craters, but despite its name and its location near known volcanoes, the actual origin of Orcus Patera is still unknown, scientists say.

The well-defined depression is about 230 miles long by 87 miles wide. It has a rim that rises up to 6,000 feet above the surrounding plains, while the floor of the depression lies about 1,500 feet below the surroundings.

Some researches say it may be a large and originally round impact crater, subsequently deformed by compression forces. Or it could have formed by the erosion of two or more closely aligned impact craters.

However, most scientists say the most likely explanation is that it was made in an oblique impact, when a small meteor or other object struck the Mars surface at a very shallow angle of less than 5 degrees.