NASA / GSFC / METI / ERSDAC / JAROS
This view of the eastern part of the Grand Canyon is based on data acquired by the ASTER instrument aboard NASA's Terra satellite on July 14, 2011.
By Alan Boyle
For years, geologists have debated just how old the Grand Canyon is, but there's no debate that the geological feature ranks among the world's top landmarks. This outer-space perspective?from?NASA's Terra satellite makes you realize just how monumental the American Southwest's grandest canyon is.
Was the Grand Canyon formed less than 7 million years ago? Or as long ago as 70 million years? The conventional wisdom has been that most of the canyon was cut by the Colorado River in the last 5 million to 6 million years. But last week, researchers said a new dating tool suggested that rocks from the canyon's western portion were eroded 70 million years ago, by an ancient river that ran in a direction opposite from the westward-flowing Colorado.
The claims add to a longstanding argument over the canyon's formation. In 2008, a different team of researchers concluded that the western Grand Canyon was carved out at least 16 million years ago???and that the eastern portion arose separately, due the uplift of the Colorado Plateau. In this scenario,?the two sections of the Grand Canyon eventually linked up to create the awesome vista we see today.?
The Terra satellite's Advanced Spaceborne Thermal Emission and Reflection Radiometer, better known as ASTER, took a close look at a section of the canyon in northern Arizona last year. The perspective you see here was produced by "draping" ASTER's color data over an elevation map developed from the satellite's stereo readings. You can just make out the traces of the Grand Canyon Village's tourist facilities amid the greenish patch at upper left.
The Grand Canyon is truly one of the world's marvels, measuring up to 9 miles (14.5 kilometers) in width and 5,600 feet (1,707 meters) in depth. For even wider-angle views, check out this 2004 image from India's Resourcesat-1 satellite, as well as this image, captured in 2000 by NASA's Multi-angle Imaging Spectroradiometer. (Get out your red-blue glasses for a 3-D look.)
These views of the Grand Canyon serve as today's treat from the Cosmic Log Space Advent Calendar, which features a daily look at Earth from space from now until Christmas. For still more Advent calendar goodies with a cosmic twist, check out The Atlantic's Hubble Space Telescope Advent Calendar, as well as the Zooniverse Advent Calendar. And be sure to click on the links below to catch up on the pictures you've missed:
Alan Boyle is NBCNews.com's science editor. Connect with the?Cosmic Log?community by "liking" the log's?Facebook page, following?@b0yle on Twitter?and adding the?Cosmic Log page?to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other science and space news coverage,?sign up for the Tech & Science newsletter, delivered via email. You can also check out?"The Case for Pluto,"?my book about the controversial dwarf planet and the search for new worlds.
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