Lying within Mare Fedunditatis (Sea of Fertility), the two craters Messier and Messier A can be seen at the centre of this image (Messier is the left one). Taken around midnight on 13th January 2009, with the moon around 16 days old, the characteristic ejecta plume shows well emanating towards the south west of the pair.

They are referred to as pristine craters because they exhibit none of the usual signs of deterioration, such as slumping crater walls, other crater impacts or basaltic lava flows. They are also rather elliptical in shape, although not along the same axis. It is believed they were created by two separate impact objects, both striking at an oblique incidence angle (around 5°).




Unfortunately the detail within the craters is not visible in the f/10 image, but instead there are some good views of the dorsa (wrinkle ridges) towards the east of the Messier pair. Dorsa are formed as compression artefacts caused by ancient tectonic movements disturbing the otherwise smooth basalt lava plains.