This image shows the layered walls and central peak of Aristarchus crater, one of the brightest features on the surface of the Moon. The crater is about 25 miles (40 km) in diameter and two miles (3.5 km) deep, and the central peak is about 1,000 feet (300 m) tall. It contains an abundance of titanium-rich minerals, which may account for its brightness. Aristarchus has also been the site of many Lunar Transient Phenomena, which are unexplained glows or haziness. They may be caused as gas below the surface escapes through cracks in the crust. This image is from the Lunar Reconnaissance Orbiter spacecraft. [NASA/GSFC/Arizona State Univ.]
Moon and Companions
Although the Moon looks quite bright in our night sky, its surface is actually one of the darkest of any major body in the solar system. On average, it reflects only about a tenth of the sunlight that strikes it back into space, making the Moon as dark as charcoal.
There is one prominent bright spot on the Moon, though - a crater named Aristarchus. Although it’s tiny as seen from Earth, it’s such a contrast to the surrounding landscape that it’s visible to the unaided eye. It’s near the lower left edge of the Moon as the Moon rises this evening, flanked by the star Spica and the planet Saturn.
Aristarchus is about 25 miles across, and a couple of miles deep. A mountain peak rises about a thousand feet from its floor. It’s surrounded by bright “rays” of debris that were blasted out by the impact that created it.
Observations by Hubble Space Telescope and spacecraft in lunar orbit show that the crater floor contains a lot of minerals that are rich in titanium. They probably came from far below the surface, and were brought to the surface by the impact.
There’s some evidence that the area around Aristarchus is volcanically active. Observers on the ground have reported seeing flashes of light or odd glows in the area, including in the crater itself. And instruments have revealed traces of a radioactive gas. That could mean that gas sometimes erupts from below the surface - briefly adding to the luster of this bright crater.
Script by Damond Benningfield, Copyright 2013
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