Tectonic Processes

East Africa is of intense interest to geoscientists investigating the formation of ocean basins and the rifting of continental plates. Conditions in some areas, such as Ethiopia, have prevented the direct inspection of the area by western field scientists for more than a decade. The broken terrain has handicapped development of transportation, leaving extensive areas isolated and inaccessible to motor vehicles. Because of these limits to research, the East African Rift is a focus for Crew Earth Observations. Photographs taken from orbit permit observation and interpretation of both geological and environmental conditions in the region.

The faults of the Red Sea system (trending North-Northwest), those of the Ethiopian rift (Northeast), and those of the Gulf of Aden (West-Southwest) originate in this region. The rift triple junction and the active volcanism in the area reflect stretching of the Earth's crust above a rising plume of hot mantle material. This rifting of continental crust is analogous to the process that separated the Americas from Eurasia and Africa to form the Atlantic Ocean.
 

East African rift zones that will be a focus of the Crew Earth Observations project include the Rukwa transform fault zone, Tanzania; Mt. Kilimanjaro, Kenya; and the rift triple junction in Ethiopia.

Analogous Features on Earth, Moon and Mars
Similar processes have produced volcanoes and impact craters on Earth, the Moon, and Mars. Others features on the different planetary bodies, such as dunes and canyons, may look alike but may not have formed by the same processes. Varying shapes and sizes of features can be due to differences in planetary density and diameter, presence or absence of an atmosphere, presence of water, and subsurface processes. Plate tectonics on Earth makes other processes more difficult to study because surface features are not preserved as well as they are on Mars or the Moon. Improved understanding of these features on the Moon and Mars will result in a fuller understanding of Earth.

Terrestrial features for which there are morphological analogues on Earth’s Moon and Mars are selected as Crew Earth Observations sites. These features include impact craters, volcanoes, dune fields, old shorelines, and expanses of layered rocks (see Canyons, Craters and Drifting Dunes).
 

By comparing detailed photos and high-resolution images of the Earth, Moon, and Mars, scientists can define the dominant processes that have shaped the landscapes of the three planetary bodies. Such analyses provide essential data for landing-site selection and for framing scientific objectives for robotic and human missions to Mars. They also aid in the identification of potentially troublesome environmental elements near proposed landing sites, such as persistent dust storms, steep slopes, or bouldered terrain.