Tag Archive | rays

Messier: The Coffee Bean Crater

bigger image

One of the must see telescopic sights on the Moon is the pair of young craters Messier and Messier A. They are located in Mare Fecunditatis and are thought to have formed from the same single low angled impactor moving right to left. The main impact created Messier and a secondary impact (either a bounce of the main impactor or separate chunk of it) created Messier A and the rays. A second (and more overhead) impact in Messier A made it a double crater. Messier crater is 1.3 km deep, 11 km long and 8 km wide. Messier A  is 11 km long and 13 km wide. The elongated shape of the craters is characteristic of a low angled impact.

Being very small they are challenging to spot in a small telescope. You are more likely to see the two prominent white rays first extending over 100 kilometers westwards from the rim of Messier A. The rays give the craters an unusual appearance often referred to as comet tails or headlights. Up close, however, the lunar Messiers take on a more dramatic appearance. New forum member JasonJason noticed Messier’s striking resemblance to a coffee bean:

Messier A (left) and Messier craters

Spot the bean…

Zoom in and examine the bouldery floor responsible for the “groove” in the bean.


NACs M104204818LC  M104204818RE

Messiers in 3D via APOD.

Different views of the Messier craters on SEDS. (Students for the Exploration and Development of Space.)

Messier A has some amazing layering on its walls as described in this NASA Article.

And in a Moon Zoo version of the Messier Marathon why not spend some time trying to spot them yourself? You will need a telescope rather then binoculars, however, a 5 day or older Moon and a clear sky. This is the view you will get through a small (90mm) telescope with a 20mm eyepiece.

Good luck!
Nice find JasonJason!


Absorb yourself in Tycho

Appropriately named after one of the most colourful characters in astronomy, Tycho Brahe, Tycho is one of the most prominent craters on the Moon with its large, bright ray system dominating the southern hemisphere. Tycho is 85 km (53 miles) in diameter and is a relatively young crater at 108 million years old. Because it is young the rays have not been degraded and dulled by meteorite and micrometeorite impacts and still have a high albedo. So extensive are the rays that samples of impact melt glass thrown out by the impact that created Tycho were collected by the Apollo 17 astronauts from the Taurus Littrow region 2,000 km away. Tycho and it’s rays are most spectacular when viewed at full Moon when the Sun is overhead.

image: jules

The Lunar Reconaissance Orbiter Wide Angled Camera gives us a very different view of Tycho. Here we see the well preserved terraced crater walls and central mountains which are just visible in binoculars. So fresh are the features in Tycho that it is the perfect place to study the mechanics of how an impact crater forms.

click for high res version from NASA.

And here’s a close up of the rugged crater floor.


More information and another close up picture in this LROC News System article.

The NAC images of Tycho are well worth a tour. There are many NAC images of the crater floor – search on Lat -43, Long -11. Here are a few to start with:

Enjoy! You may be some time!

Jules is a volunteer moderator for the Moon Zoo forum