One billion years ago, give or take a couple of hundred thousand years, a small asteroid, perhaps only a few hundred meters wide, hurtled in, low over the eastern lunar limb, impacting into the basalt plains of Mare Fecunditatis. The very slight angle of incidence into the mare resulted in an excavation of the elliptically shaped 9 by 11 km Messier crater in an explosion of ejecta, shooting laterally to the north and south sides of the crater as well as down range to the west. This butterfly pattern of rays are common in low angled impacts. In addition, the forward moving ejecta falls ahead in the direction of the impactor, creating forward facing rays. From Messier this down range ejecta appears to have impacted into the western rim of an pre-existing crater, In just a a few milliseconds itâ€™s once relatively round rim was modified into the egg shaped, 13 x 11 km Messier A. Two rays developed as the ejecta was deflected off the rim, continuing for over 100 km and vanishing somewhere near Lubbock and Leaky.
Subject: Messier and Messier A (formerly W.H. Pickering) Rukl: 48
Date: 5-30-09 Time: 4:55 to 5:40 UT
Seeing: Antoniadi II-III Weather: clear
Lunation: 4.66 days
Colongitude: 330.2 deg.
Lib. in Lat.: +01 deg. 44 min.
Lib. in Long.: +03 deg. 32 min.
Phase: 115.7 deg.
Telescope: 12" Meade SCT f/10
Binoviewer: Denkmeier BV-25 with 2X nosepiece
45 deg. W.O. erect image diagonal
Eyepieces: Pentax XW 20mm
Medium:Sketch White and black Conte' on Black 400 Strathmore Artagain paper
Sketch size: 9" x 12"