Messier is an oval crater elongated in an E-W direction. Its size is 9 x 11 km and it apparently originated as the result of an oblique meteorite impact from space. Messier "A" comprises two circular craters: The younger, eastern crater overlaps part of the smaller, older formation. This twin crater measures 11x13 km. To the west , two straight narrow rays, resembling the tail of a comet, trail across the surface of Mare Fecunditatis to a distance of about 120 km.
This medium power scan showing all of Section 48, including Messier & Messier A
was obtained by The Lunascan Project with its 16" Newtonian on April 23rd, 1996.
My first impression from these images was that a multiple impact occurred, one preparing the next one for a penetration that deflected upward when it struck a harder lunar surface and produced the second crater and ejecta which forms some of the rays. Some of images show the "horns" where the second impact reshaped the crater. Since crater chains are common on the Moon, this seemed logical and that the impactor penetrated a ridge-like structure. However, other images show the "ridge" at right angles to the one above, so this may not be a ridge at all, but some type of optical illusion. Also, the proposed "exit crater" is the doublet, just the opposite of what one would suspect if two impactors struck the same spot and left, streaming ejecta from the single exit crater.
The Lunar Orbiters took some great photographs of the lunar surface. LO-1 recorded a beautiful panorama that showed the crescent Earth in the distance, and Lunar Orbiter 2 took a stunning oblique view of the crater Copernicus. Less familiar, however, is this photograph by Lunar Orbiter 5 looking westward across Mare Fecunditatis (Sea of Fertility). It captures the twin craters Messier and Messier "A" (the latter a pancake of one crater on another) which have intrigued lunar observers for centuries. The horizontal lines represent the "framelets" produced by the scanning system.
The following images are all from the Apollo
Not too spectaculer, but still interesting, is the first Apollo image I located, from Apollo 8, AS08-13-2341 . But quite stunning was the next one, the actual image number I do not know, AS8mess.
Next are six Apollo 10 images:
AS16-4471 (P) AS16-4469 (P)
"Differences between the two parts
are more closely shown in this oblique view of Messier "A" composed
of a stereogram. Both Messier and Messier "A" resemble some small
experimental impact craters produced in sand by projectiles following
shallow trajectories (4-degrees or less from the horizzontal) at
velocities of approximately 1.7 km/s. In separate experiments using
single projectiles, both elliptical craters with lateral ejecta lobes
and doublet craters have been produced. Thus, it can be inferred
that these lunar craters were produced by high-velocity projectiles
following shallow trajectories. By further anology with the experiments,
the projectiles that formed Messier and Messier "A" apparently traveled
east to west. -H.J.M. (3) The images
were taken on April 23, 1972."
Finally, the Clementine spacecraft
was the latest mission to collect images of Messier & Messier
"A" in 1994:
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