How Earth Got its Oxygen
Clues to origin of life revealed in Tagish Lake meteorite
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Vida y fosilización en el desierto antártico.
Carmen Ascaso, Centro de Ciencias Medioambientales, CSIC, y Jacek Wierzchos, Universitat de Lleida. Artículo publicado en la revista El Ecologista nº 43, primavera 2005
Los estudios llevadas a cabo por los autores en la Antártida están sirviendo para sentar las bases sobre las técnicas que permitan detectar formas y restos de vida en Marte o en los meteoritos. ...(more)
Over the Kimberley Region of northern Western Australia, satellite sensors and airplane passengers alike can see a giant arachnid sprawling over the arid landscape. This spider’s not just big, it’s old. This prehistoric monster crawls out of the past as if to remind us of the destructive power of the cosmos.
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite captured this image of Spider Crater and its surroundings on August 11, 2000. In this false-color image, the arid landscape appears in varying shades of crimson. Water appears blue-black, namely in the meandering river near the bottom edge of the image. Vegetation appears in shades of red. While vegetation looks sparse throughout the area, the intense red dots along the river indicate fairly lush—if intermittent—vegetation lining the riverbanks.
Near the center of the image is the Spider, sunlight giving an oddly ghostlike appearance to the steep ridges that form its legs. Geologists long puzzled over what this structure was, but found an important clue in the 1970s. They found shatter cones—cone-shaped, grooved rocks known only to appear in craters left by meteor or asteroid impacts. Other clues to the structure’s origin appeared in the form of strongly deformed layers of sedimentary rock that showed evidence of extraterrestrial trauma.
Spider Crater rests in a depression some 13 by 11 kilometers (8 by 7 miles) across. Meteorite craters often have central areas of uplift, and Spider Crater fits this pattern, with a central dome roughly 500 meters (1,640 feet) in diameter. Radiating from this central dome are features unusual in impact craters in general, but important in giving this crater its nickname. Overlapping beds of tough sandstone that have weathered the elements far better than the surrounding rocks form the spider’s “legs.” So while Spider Crater sits in a depression and has a central uplift area characteristic of impact craters, it shows extreme differences in erosion, giving it a unique appearance.
The age of Spider Crater is uncertain, but its formation has been estimated to fall between 900 and 600 million years ago. If this age estimate is correct, the crater formed from an impact that occurred during the Neoproterozoic, a period of geologic history when, some geologists hypothesize, Earth underwent a series of global ice ages nicknamed “Snowball Earth.”
NASA image created by Jesse Allen, using data provided courtesy of NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team. Caption by Michon Scott.
Source: http://earthobservatory.nasa.gov/IOTD/view.php?id=8607
Planetary scientists are pretty sure that almost all of the HED meteorites come from the fourth-largest asteroid, 4 Vesta. HED stands for the three types of rocks that make up the group. As cosmochemists have studied the meteorites over the years, their view of the geologic history of the asteroid has become progressively more complicated. Jean-Alix Barrat and Marcel Bohn (CNRS and University of Brest, France), Philippe Gillet (CNRS and Ecole Normale Supérieure de Lyon, France), and Akira Yamaguchi (National Institute of Polar Research, Tokyo, Japan) have found that Vesta is even more complicated--and interesting--than we thought. ... (more) http://www.psrd.hawaii.edu/June09/Vesta.granite-like.html
By Derek Jordan and Ted Morris
Herald/Review
Published/Last Modified on Thursday, Jun 25, 2009 - 02:18:09 am MST
SIERRA VISTA — A number of southeastern Arizona residents reported seeing a bright meteor in the night sky Tuesday, followed by a loud explosion-like sound as it fell to Earth. ... more
http://www.svherald.com/articles/2009/06/25/news/doc4a430805ea916104103851.txt
Numerous people called in to news stations and police last night, around 9:20 pm, when a bright fireball lit up the skies over Tucson. It may have been a chunk of cosmic debris, or it could have been a satellite or pieces of space junk burning up in the atmosphere. ... (more)
http://tucsoncitizen.com/lizard/tag/arizona-meteor/