Moonwatch
Don’t overlook crater Rutherfurd.
“There is a curious, curving progression of craters formed in different eras”
At 55km across, Rutherfurd isn’t exactly a small crater. However, its location on the southeast rim of 225km Clavius tends to mean it’s somewhat overlooked. Clavius is a favourite target for all sizes of telescope because it’s large, easy to find and full of interesting detail. In particular there is a curious curving progression of craterlets, formed from impacts of different ages, starting at 12km Clavius J, moving onto 13km Clavius N, 21km
Clavius C and 28km Clavius D. Rutherfurd ends the arc and its inclusion in what is essentially a craterlet sequence is probably another reason why it tends to be disregarded in favour of its larger host.
Rutherfurd is a well-defined, young crater named after Lewis Rutherfurd who took the first photographic images of the Moon through a telescope. The crater’s sharp, crenulated, oval rim has a long axis orientated roughly north-south. It has a 1km high ‘central’ peak offset northeast of Rutherfurd’s true centre. The rest of the floor has a level approximately 1km below that of Clavius. It appears quite rugged with small hills to the north and a larger more contiguous, wave-like region covering approximately onethird of the floor area towards the south.
Large smooth patches on Rutherfurd’s floor are most likely the result of lava melt pools, regions where molten lava has flowed, levelled and cooled. The region to the north, and more particularly northwest, of the crater’s ‘central’ peak is particularly bumpy with many small hills. These are easier to see when the lunar terminator is nearby.
To the south of Rutherfurd lie its allocated sub-craters; 10km
Rutherfurd A, 6km B, 13km C, 9km D and 9km E. The region to the north is interesting because of the ejecta pattern that appears to extend north towards 53km Porter. This pattern takes the appearance of a number of shallow channels and bumps stretching northwards. The texture of the channels under high-resolution suggests they are made from closely overlaid craterlets. This is particularly evident along the channel that passes from Rutherfurd but is interrupted by Clavius D. These features are extremely narrow and best seen through large telescopes when the surface lighting is oblique.
Porter is another crater that interrupts Clavius’s rim, this time to the northeast, mirroring Rutherfurd across the horizontal axis of the elliptical-looking Clavius. In reality Clavius is quite round, its elliptical appearance the result of foreshortening due to its proximity to the southern limb. The same effect adjusts our view of Rutherfurd and Porter, but as the latter is nearer the lunar equator, it appears less distorted and slightly larger. Porter is, in fact, a tad smaller than Rutherfurd.