Posts Tagged ‘Impact Crater’

An amazing view of an impact crater as seen on the planet Mars on July 9th from NASA’s Mars Reconnaissance Orbiter. MRO has been orbiting the red planet since August 12th 2006 and providing the best images yet from its High Resolution Imaging Science Experiment camera (HiRISE). This image was one of six released today.

What caused the central pit within this impact crater: unusual subsurface layering or a lucky second impact?

Impacts into layers of alternately strong and weak material – for example, ice rich versus non-ice-rich – produce terracing such as that seen between the inner pit and the outer rim. Scientists have used terraced craters to estimate the thickness of lava flows on the Moon and elsewhere. Uneven sublimation and periglacial erosion of exposed ice-rich material in the interior of the crater may explain why the small central pit is slightly offset from center relative to the terrace and rim of the larger crater.

The pit in the center of the main feature could also be from a later impact crater striking inside and slightly off-center from the original. It has a raised rim, which is characteristic of impact craters and is difficult to explain with a layered target. While no ejecta from this later impact can be seen, the ejecta could have been removed by extensive periglacial modification. Additionally, the floor fill around the inner crater resembles impact ejects elsewhere at this latitude, and some of the “landslides” to the East could be flow-back of ejecta off the walls of the larger crater.

Written by: Sarah Milkovich

LCROSS and its Centaur upper stage will crash into the moon in just an hour (At the time of this writing), live coverage has started and you can watch it here. Before that though, we’ve impacted the moon before with another upper stage. Below is an image taken by LROC of that impact crater.

A distinctive crater about 35 m in diameter was formed when the Apollo 14 S-IVB (upper stage) was intentionally impacted into the Moon. The energy of the impact created small tremors that were measured by the seismometer placed on the Moon by Apollo 12 astronauts.

The interior of the crater has bright mounds and a bright ejecta blanket surrounds the exterior of the crater. Bright rays are observed to extend across the surface for more than 1.5 km from the impact. This image was taken when the Sun was relatively high in the sky (illumination angle of 25.1°) bringing out subtle differences in albedo (reflectivity or brightness). The Apollo 16 spacecraft first photographed this crater (Pan Camera frame 5451) and scientists noted the unusual occurrence of dark rays mixed with bright rays. Can you find the dark rays?