Friday, November 12, 2010

The Central Peak of Kepler

Boulders and simple craters perched on top of Kepler crater's central peak. LROC Narrow Angle Camera (NAC) observation M111843702R, LRO orbit 1616, November 2, 2009; field of view (below and HERE) is 500 meters [NASA/GSFC/Arizona State University].

Drew Enns
LROC News Service

There are two basic types of impact craters: simple and complex. Simple craters form a bowl-like rimmed depression, and complex craters (such as Kepler) display central peaks, terraces, and flat floors. Complex craters occur above a certain diameter crater, the cutoff diameter is dependent on gravity, so it varies from planet to planet (or moon to moon). On the Moon the size cutoff between simple and complex craters is between 10 and 20 km, on the Earth it is between 2 and 5 km.

A full-sized segment of an Apollo 12 orbital shot featured in previous postings from Drew Enns discussing Kepler. From this foreshortened angle (see context below) it's easier to see the minimal central peak does not exceed the crater's rim in elevation [NASA/LPI].

An LROC Wide Angle Camera mosaic of Kepler with an arrow indicating the location of featured NAC image above can be viewed HERE.

Despite the label "central peak," a central peak is not always exactly in the center of a crater, nor is it always symmetrically shaped; Kepler crater is an example. Instead of having a nice central peak, Kepler crater has an irregular off-center peak. This form is most likely due to the crater being close to the boundary diameter between a simple and complex crater. Larger craters, such as King crater, can also display oddly shaped central peaks that are likely the result of an oblique impact.
Browse the whole NAC image of Kepler crater and inspect the landforms associated with its central peak. Can you find evidence of impact melt on the central peak, terraces, and floor?

Related Posts:
Concentric crater
Kepler Crater Ejecta
Kepler's Rim