A successful effort to map Earth from orbit has provided the clearest evidence yet of an impact crater long thought to be the product of an asteroid or comet that smacked into Central America 65 million years ago, dooming dinosaurs everywhere.
The partial outline of the Chicxulub crater appears as a gentle curve across the Yucatan Peninsula in a map generated by the Shuttle Radar Topography Mission (SRTM). That mission used three-dimensional radar system to measure 80 percent of the Earth's surface from orbit aboard the Space Shuttle Endeavour.
"When we first look at the Peninsula, it's as flat as pancake," said SRTM project scientist Michael Kobrick during a telephone interview. "It's basically a limestone plateau."
But the region is also home to Chicxulub, a crater spanning 112 miles (180 kilometers) with a maximum depth of 3,000 feet (900 meters) at its center, off the coast of the Yucatan. The edge of the crater is only a few meters deep spread out over the course of three miles (5 kilometers).
"If you walked across it, you probably wouldn't even know it was there," Kobrick said.
Satellite data and gravity mapping allowed scientists to identify the crater in the 1990s, the existence of which was first suggested my Luis Alvarez as an explanation for dinosaur extinction in 1983. According to some theories, the impact collision may have killed off vegetation, led to acid rain from sulfuric clouds or caused global forest fires that in turn killed off the dinosaurs.
In addition to observing Chicxulub, SRTM churned out more than eight terabytes of topographical measurements during its February 2000 ride aboard Endeavour. The sheer amount of data has taken three years to analyze and should provide the most detailed maps of the Earth when complete. Then, SRTM researches said, the level of topographical detail for other countries should be up to par with that of the United States.
"In the United States, we're kind of spoiled," said Kobrick, adding that US satellites have provided detailed maps for the country. "You can pretty much walk into any hiking store and pick up accurate and detailed maps of elevations, roads and trails."
But that isn't true for other countries, aside from those in Western Europe, where detailed topography has been unavailable. Some flight maps in South America, for example, warn pilots that mountain elevations in some areas are only thought to reach 15,000 feet, though they could be higher, Kobrick said.
"This project has been able to measure the Earth at a greater clarity than anything we had before," said Eric Berryman, a spokesman for the National Imaging and Agency that worked with NASA on the project.
SRTM researchers are releasing their Earth imagery a continent at a time, starting with North America. They expect to complete topographical maps of South America in the next five weeks.
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