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(meteorobs) FW: NASA'S NEWEST MAPS REVEAL A CONTINENT'S GRANDEUR AND A SECRET


> RELEASE: 03-096
> 
> NASA'S NEWEST MAPS REVEAL A CONTINENT'S GRANDEUR AND A SECRET
> 
>      From Canada to Central America, the many grandeurs of 
> North America's diverse topography star in a just-released 
> high-resolution map from NASA's Shuttle Radar Topography 
> Mission (SRTM). But a relatively obscure feature, all but 
> hidden in the flat limestone plateau of Mexico's Yucatan 
> Peninsula, is what emerges as the initial showstopper from 
> the mission's first released continental data set.
> 
> The existence of the impact crater, Chicxulub, was first 
> proposed in 1980. In the 1990s, satellite data and ground 
> studies allowed it to gain prominence among most scientists 
> as the long sought-after "smoking gun" responsible for the 
> demise of the dinosaurs and more than 70 percent of Earth's 
> living species 65 million years ago. The SRTM has provided 
> the most telling visible evidence to date of a 180-kilometer 
> (112-mile) wide, 900-meter (3,000-foot) deep impact crater, 
> the result of a collision with a giant comet or asteroid on 
> one of Earth's all-time worst days. 
> 
> The North America and Yucatan Peninsula images created from 
> the map are available on the JPL Planetary Photo journal at: 
> 
> http://photojournal.jpl.nasadot gov/catalog/PIA03377
> http://photojournal.jpl.nasadot gov/catalog/PIA03379
> 
> "This new, complete North American data set greatly expands 
> our topographic knowledge of Canada, southern Alaska and its 
> Aleutian Islands, Mexico and Central America," said Dr. 
> Michael Kobrick, SRTM project scientist at NASA's Jet 
> Propulsion Laboratory (JPL), Pasadena, Calif.
> 
> "There are spectacular features that pop out in these maps as 
> never before, and more subtle features, like Chicxulub, 
> become apparent for the first time. In fact, much of the 
> surface expression of Chicxulub is so subtle; if you walked 
> across it you probably wouldn't notice it. That's where the 
> view from space becomes invaluable, " Kobrick said.
> 
> The Chicxulub data show a subtle, yet unmistakable, 
> topographic indication of the impact crater's outer boundary: 
> a semicircular trough 3 to 5 meters (10 to 15 feet) deep and 
> 5 kilometers (3 miles) wide. Scientists believe the impact, 
> centered off Yucatan's coast in the Caribbean, disturbed the 
> subsurface rocks, making them unstable. The rocks were 
> subsequently buried by limestone sediments, which erode 
> easily. The crater rim's instability caused the limestone to 
> fracture along the rim, forming the trough. In addition, the 
> collapse of numerous limestone caverns above the crater rim 
> resulted in an arcing chain of sinkholes, called cenotes, 
> that are visible as small, circular depressions. 
> 
> Exactly how the Chicxulub impact caused Earth's mass 
> extinctions is not known. Some scientists think it threw 
> massive quantities of dust into the atmosphere, blocking the 
> sun and stopping plants from growing. Others believe sulfur 
> released by the impact lead to global sulfuric acid clouds 
> that blocked the sun and also fell as acid rain. Another 
> possibility is global wildfires triggered by atmospheric 
> reentry of red-hot debris.
> 
> The remainder of the North American data paints a dynamic 
> portrait of a geologically complex continent. Active 
> structural deformations of Earth's crust along and near the 
> Pacific/North American tectonic plate boundary create the 
> diverse topographic relief of the Pacific coast. Across the 
> Great Plains, erosional patterns dominate, with stream 
> channels surrounding and penetrating remnants of older smooth 
> slopes. In Canada and the northern U.S., evidence of glaciers 
> from the last ice age abounds. 
> 
> In February, NASA finished processing the mission's data and 
> delivered it to the National Imagery and Mapping Agency 
> (NIMA). More than eight terabytes of data recorded aboard the 
> Space Shuttle Endeavour were refined into 200 billion 
> research-quality measurements of Earth's landforms. The NIMA 
> will perform additional data finishing and send it to the 
> U.S. Geological Survey's Earth Resources Observation Systems 
> Data Center, Sioux Falls, S.D., for final archiving and 
> distribution. South America will be the next continental 
> dataset.
> 
> The SRTM, flown Feb. 11 to 22, 2000, made 3-D measurements of 
> the more than 80 percent of Earth's landmass located between 
> 60 degrees north and 56 degrees south of the equator; areas 
> home to nearly 95 percent of the world's population. SRTM is 
> a cooperative project of NASA, NIMA, the Department of 
> Defense, the German and Italian space agencies. Fulfilling 
> part of NASA's mission to understand and protect our home 
> planet, it is managed by JPL for NASA's Earth Science 
> Enterprise, Washington. The California Institute of 
> Technology in Pasadena manages JPL for NASA.
> 
> For more information about SRTM on the Internet, visit:
> 
> http://www.jpl.nasadot gov/srtm/
> 
> -end-
> 
>                             * * *
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