Crater Chains on the Earth and Moon

Summary:

Recent reports suggest that crater chains exist on Earth, possibly formed by weak asteroids or comets tidally stretched apart by the Moon (analogous to comet Shoemaker-Levy 9 at Jupiter) with the resulting fragment trains proceeding directly to strike the Earth. By modeling close encounters between strengthless particulate bodies held together by self-gravity and planets like the Earth and Moon, we find that the rate of formation of lunar crater chains is ~10 times the corresponding terrestrial rate. The number of known lunar crater chains (~1) and the relative youth of the Earth's surface together suggest that terrestrial crater chains, if they exist, form by another process.

Possible Crater Chains on the Earth?

A crater chain is a regularly spaced row of three or more impact craters with similar sizes and apparently identical ages. Crater chains are formed when a weak asteroid or comet is tidally disrupted during a close approach to a planet, separating into a chain of fragments which, by chance, hit a moon or the planet rather than escaping into interplanetary space
Recent work indicates that crater chains may exist on Earth as well. Eight circular depressions (3-17 km wide) distributed along a 700 km line across Kansas, Missouri, and Illinois may comprise part of a crater chain (M.R. Rampino and T. Volk (1996) Geophys. Res. Lett. 23, p. 49.) Two of the eight structures (Decaturville and Crooked Creek in Missouri) are known from field studies to be impact craters ~300 Myr old.

Possible crater chain stretching across Missouri:

A second study using radar imagery of the 17 km diameter, 360 Myr old Aorounga impact crater in northern Chad discovered a ~10 km wide circular structure adjacent to the Aorounga crater and a second, less distinct feature somewhat displaced from the line defined by the other two {S.C. Ocampo and K.O. Pope (1996) Lunar Planet. Sci. XXVII p. 977). Field work to verify that the new structures are impact craters has not been attempted, but it is possible that they and Aorounga are members of a crater chain.

Possible crater chain foudn in Chad:

Crater Chains on the Moon:

The Davy Crater Chain

The Davy crater chain (arrow) is one of the most spectacular chains of craters on the Moon. It extends for about 50 km across the floor of the large. very old Davy Y crater and onto its eastern rim. The simple geometry of the Davy chain, its symmetry, and the uniform spacing of its individual craters argue for an origin similar to the crater chains found on the Galilean satellites. The Davy chain is a lone feature, with no other chains with similar trends in the area. Secondary chains tend to occur in large numbers within the belt of secondary craters surrounding a primary crater.

Another Interesting Lunar Crater Chain

This is am image of a crater chain about 500 km north of Tsiolkovsky on the far side of the Moon. For scale, the crater in the near the upper left corner is about 26 km wide. The origin of this chain is controversial. The lack of herringbone ridges make it less likely to be a secondary. No faulting is observed which would control the alignment of the craters, nor is any volcanic ejecta, making it unlikely to be of volcanic origin.