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Messier and 'Messier A' from Apollo 11 '' NASA  photo''
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19
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S
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476
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E
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9 × 11 km
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13 km
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313
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is a relatively young lunar
Impact Crater located on the
Mare Fecunditatis . The crater has a discernable
Oblong shape that is not caused by foreshortening. The longer dimension is oriented in an east-west direction.
Just to the west lies 'Messier A', a similar-sized crater with an oblong, doublet form. The longer dimension of this crater is oriented north-south, at
Right Angle s to Messier crater. This crater also has a curved bulge extending to the west.
The interior of craters Messier and Messier A have a higher albedo than the surrounding
''maria'' . There is also a dark streak in the center of each crater. Two prominent, nearly linear
Rays extend westward from the rim of 'Messier A', continuing over 100 kilometers toward the east edge of
Mare Fecunditatis . The ''maria'' about the craters is also lightly marked by rays from other craters.
It is theorized that Messier crater was formed by an impact at a very low angle, and that 'Messier A' could have formed following a rebound by the impacting body. The low angle of impact may also explain the asymmetrical ray system.
To the northwest of 'Messier A' is a long, narrow
Rille .
By convention these features are identified on lunar maps by placing the letter on the side of the crater mid-point that is closest to Messier crater.
The following crater has been renamed by the
IAU .
In the past 'Messier A' has been called the
W. H. Pickering Crater , but this was never officially sanctioned by the IAU. A different
Crater has since been named for Pickering.
