OCTOBER 20, 1997


Scientists using a variety of spaceborne remote-sensing images, combined with limited ground research, have discovered what they think is a possible impact crater in a dry river bed in the Yemen Arab Republic.

"On the remote-sensing images, the proposed crater appears as a 770-meter-diameter (2,525-foot) circular feature centered on a small wadi or dry river channel. Although sharp on the remote-sensing images, the feature is unremarkable in the field," said Dr. Ronald Blom, a research geologist at NASA's Jet Propulsion Laboratory. "This is another example of how remote-sensing tools help us see things we wouldn't normally be able to detect, or might overlook, on the ground."

Blom and his colleague Dr. Robert Crippen, also of JPL, are presenting their findings this week at the annual meeting of the Geological Society of America, being held in Salt Lake City. The image is available at

They used radar images from the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the space shuttle in 1994, and enhanced visible and near- infrared images from the Landsat Thematic Mapper satellite.

"A very brief field reconnaissance in January 1997 indicates, but does not confirm, that the feature may well be an impact crater," Blom explained. "The crater is in a wadi that is filled with sediment and windblown sand. No direct evidence of an impact, such as overturned rims, shatter cones, or meteoritic material, were observed. However, large circular features are uncommon. Other potential explanations for this circular feature include a sinkhole or volcanic crater. But there was no field evidence of volcanic or sinkhole activity. Thus, neither seems likely in this case."

SIR-C/X-SAR, a joint mission with NASA and the German and Italian space agencies, is managed by JPL, a division of the California Institute of Technology, for NASA's Office of Mission to Planet Earth, Washington, DC. Blom's field work was sponsored by New Wave International and the Kaplan Fund.

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