Messier & Messier A

Section 37 & 48 and Messier & Messier A. Image by Legault

Francis Ridge:
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 missions: 

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:


The next three Apollo 11 images are extremely good:


The three Apollo 15 images are less impressive, but the first one of this series is our first overhead view which provides valuable detail.


Next are three fascinating images from the Apollo 16 mission. The first shows the wide region of Mare Fecunditatis in 
AS16-121-19449.  The next one shows part of the Lunar Excursion Module with Messier  in the background  in  AS16-122-19533 .  The latter includes the ascent stage of the Apollo 16 LM as it approached the Command/Service modules (CSM) during rendezvous, with a contrasting background of darkness and the moon's Sea of Fertility (Mare Fecundatatis). Taken from the Command and Service Module, the photo shows the aft side of the LM during a yaw maneuver. Note the buckled thermal panels. Messier and Messier A (right center) are among the most readily identifiable features on the surface below.

And then this blockbuster

The caption states that the "east part of this doublet has steep, bright walls, whereas the west part is dark and appears mantled."

                                              AS16-4471 (P)                                                                           AS16-4469 (P)

A stereo pair by Apollo 16

Original, full-sized image. Click here

"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:

Image #1
Image #2 an enlargement
To see VGL/Jon Floyd's theory/cooments, click here

For the latest great images, reports, and other information on Section 48, click here:

Section Directory 48

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