From the article by The Planetary Society...
The Vichada River snakes slowly through the thick foliage of the Colombian jungle. It twists and turns through the marshy plains, never deviating from its constant western course. Only in one place, at the center of Vichada province in Eastern Colombia, does the river vary from its westward flow: there it shifts suddenly southward and for dozens of kilometers follows the arc of a near-perfect semi-circle. Finally, it straitens out and resumes its normal flow on its way to join with the mighty Orinoco.
It was January of 2004 when the elegant curve of the Vichada first caught the attention of geologist Max Rocca of Buenos Aires. Rocca at the time was searching for traces of ancient asteroid impacts in South America, a task made exceptionally challenging by the jungle growth that covers much of the continent and obscures the outlines of mountains and depressions. While pouring over images from the Landsat 5 satellite, which were posted on the website of NASA’s John Stennis space center, Rocca noticed the circular arc of the Vichada River. This, he realized, might be a clue: Perfect geometrical contours are rare in nature, and the presence of such a curve on the Vichada was suggestive. Could it be that the course of the river was shaped by the circular outlines of an impact crater? Rocca decided to find out.
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Max Rocca is not a traditional geologist. He is not employed by a university department, and his work is not sponsored by any government agency or mining and drilling company. The 43 year-old Argentinian is a private citizen who makes his living as a systems analyst, and although it has been years since his days as a student of geology at the University of Buenos Aires, his fascination with the structure of the Earth never waned. In 2002 he applied for a grant from The Planetary Society to help him search for impact craters in the jungle-covered terrain of South American. To us at the Society he seemed like a perfect candidate – an amateur with the skills of a professional, someone who will make the best use of the resources we can provide. We quickly granted his request, and have been funding his work continuously for the past 8 years. Rocca, for his part, did not disappoint, and has been producing a steady stream of discoveries ever since.
Rocca specializes in the study of satellite images and aerial photographs of remote regions, and time and again he has demonstrated his remarkable talent for seeing what others cannot. In 2007, for example, in Patagonia in central Argentina, he located the largest impact crater field in the Southern Hemisphere. Known as Bajada del Diablo, the field was originally detected in 1987 by Hugo Corbella, and contains more than 100 craters ranging from 100 to 500 meters in diameter. Rocca then joined forces with a group of geologists from Argentinian research centers who travelled to the region, and in 2009 they jointly published a paper about the crater field in the journal Geomorphology. Along with team member Rogelio Acevedo of the Southern Center for Scientific Research (CADIC) in Tierra del Fuego, Rocca is now working to produce a complete catalog of South American impact craters.
Link: Planetary Society Researcher Discovers Largest Crater in South America
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