Featured Image - 02/26/2008
Lunar Mare Wrinkle Ridges: Waves on the Lunar Seas
Wrinkle ridges are commonly found in nearly all of the lunar maria. Scientists have long puzzled over the origin of these long (10s to 100s of kilometers) linear hills. If you were a future lunar explorer traveling across a wrinkle ridge, you would gradually rise up across a broad arch and most likely find another narrower yet steep ridge to cross. Oddly enough, wrinkle ridges can be oriented both radially (like the points of a star) and concentrically (like the rings of a bulls-eye) from the centers of the circular mare-filled basins. The association between the wrinkle ridges and mare basalts has led to the suggestion that there is a relationship between the basalts and the ridges. Lunar scientists now think that wrinkle ridges are tectonic landforms, caused when the mare lavas subsided and contracted. This contraction results in a combination of folding and faulting of the emplaced mare basalts.
The prominent wrinkle ridge shown in this Metric camera image is an example of a concentric wrinkle ridge named Dorsa Aldrovandi that is found near the eastern margin of Mare Serenitatis. This ridge is associated with a significant elevation change on the mare surface: the elevations on the basin interior side (that is, on the western side) of the ridge are significantly lower than the elevations on the eastern side of the ridge. This elevation change is larger than usually seen with other wrinkle ridges, which means that the large elevation change seen across Dorsa Aldovandi may actually express a more deeply rooted fault. The high resolution images and topographic data that will be returned by the Lunar Reconnaissance Orbiter, coupled with field investigations by future human lunar explorers, will greatly improve our understanding of how wrinkle ridges like Dorsa Aldrovandi form.
The position of Dorsa Aldrovandi, a large lunar mare wrinkle ridge, is highlighted in this Apollo 15 Metric Mapping frame (Apollo Image AS15-M-0394[NASA/JSC/Arizona State University])