No. 37: Jan-Feb 1985
Rhythmic layered deposits can be seen in the Valles Marineris, a large Martian valley. The strata are erosional remnants up to 5 kilometers high, with individual layers 170-220 meters thick. They can be traced on spacecraft photographs for some 50 kilometers. The material making up the strata is clearly different from that of the valley walls. After the layers were deposited, they were deeply eroded by some event in Martian history that seems related to the formation of the great outflow channels associated with Valles Marineris. The author of this American Geophysical Union paper concludes:
"The morphology and history of the sediments are consistent with deposition in standing bodies of water early in Martian history."
(Nedell, Susan S., and Squyers, Steven W.; "Geology of the Layered Deposits in the Valles Marineris, Mars," Eos, 65:979, 1984.)
Comment. The "event" that deeply eroded the Martian deposits may have been similar to the catastrophic emptying of Lake Missoula, which carved out the Channelled Scablands of eastern Washington state as the Ice Ages waned.