Volcanic Activity Shaped Mercury After AllJuly 07, 2008PROVIDENCE, R.I. [Brown University] - Scientists have long anguished over how little is known about Mercury, the innermost of the four terrestrial planetary bodies in our solar system. The gaps in knowledge covered such basic information as the planet's geology, how it was formed and evolved and whether its interior was still active. In 1975, the Mariner 10 spacecraft returned intriguing images that showed smooth plains covering large swaths of Mercury's surface. But scientists could not determine whether the plains had been created by volcanic activity or by material ejected from below the surface when objects had collided into it. Thus, they could not reach a consensus over Mercury's geologic past. Now, a research team led by Brown University planetary geologist James Head has determined that volcanism played a central role in forming Mercury's surface. In a paper that appears in the July 4 issue of Science, part of a special section describing the MESSENGER spacecraft's first flyby of Mercury, the researchers have found evidence of past volcanic activity, suggesting that the planet underwent an intense bout of changes to its landscape about 3 to 4 billion years ago - and that the source for much of that reshaping was within. "What this shows is that Mercury was not dead on arrival," says Head, the paper's lead author. "It had a pulse for a while. Now, we want to know when it had that pulse and what caused it to slow down and eventually stop." A major clue to Mercury's geologic past came from the scientists' finding of volcanic vents along the margins of the Caloris basin, one of the solar system's largest and youngest impact basins. The group zeroed in on a kidney-shaped depression that was surrounded by a bright ring, lending a halo-like impression to the landscape. The scientists determined that the depression was a volcanic vent, and the bright ring around it was pyroclastic, remnants of lava that had been spewed outward, much like a volcanic fountain on Earth. Another larger ring surrounding the vent and halo ring showed that another type of volcanism, called effusion, in which molten rock from within the planet oozes outward and covers the surface, had occurred. Together these deposits create a surface feature shaped like a volcanic shield - a clear sign to scientists that volcanic activity helped form the surrounding plains. Mariner 10 snapped pictures of roughly 45 percent of Mercury's surface. MESSENGER (an acronym for MErcury Surface, Space ENvironment, GEochemistry, and Ranging), which flew past Mercury last January, mapped 20 percent more of the planet, in the process taking more detailed, higher-resolution images of its surface. (The spacecraft is scheduled for two more flybys of Mercury and a yearlong orbit of the planet in March 2011.) Armed with the higher quality images and greater coverage, Head and his team write that they found many impact craters and areas between craters that were flooded with lava, bolstering their belief that volcanism had been widespread on Mercury and had contributed significantly to the planet's formation. In one such area, the team examined circular wrinkle ridges outlining an impact crater roughly 60 kilometers in diameter and filled to the rim with material. Similar patterns are found on the Moon and on Mars, and they indicate that the craters were flooded by volcanic activity. If that is the case with the wrinkle-ridge ring on Mercury, the scientists say, the finding suggests that the crater is filled with lava about 2.7 kilometers deep. "That's a lot of lava," Head says. "It shows the planet was really active in its early history." The new insights will help scientists link Mercury's surface evolution to its interior history and to compare the planet with the geologic histories of the Earth, Venus, the Moon and Mars. The NASA Discovery Program funded the MESSENGER mission and the research. Brown University |
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| Related Volcanic Activity Current Events and Volcanic Activity News Articles Study uses satellite imagery to identify active magma systems in East Africa's Rift Valley A team from the University of Miami, University of El Paso and University of Rochester have employed Interferometric Synthetic Aperture Radar (InSAR) images compiled over a decade to study volcanic activity in the African Rift. The study, published in the November issue of Geology, studies the section of the rift in Kenya. Rice U. lab leads hunt for new zeolites In all the world, there are about 200 types of zeolite, a compound of silicon, aluminum and oxygen that gives civilization such things as laundry detergent, kitty litter and gasoline. But thanks to computations by Rice University professor Michael Deem and his colleagues, it appears there are -- or could be -- more types of zeolites than once thought. Clemson researchers say algae key to mass extinctionss Algae, not asteroids, were the key to the end of the dinosaurs, say two Clemson University researchers. Geologist James W. Castle and ecotoxicologist John H. Rodgers have published findings that toxin producing algae were a deadly factor in mass extinctions millions of years ago. Scientists measure the rate of ascent of volcanic magma Plinian volcanic eruptions are notoriously destructive. These very powerful eruptions often occur after long periods of quiescence and are preceded by relatively short periods of seismic restiveness. The greenhouse gas that saved the world When Planet Earth was just cooling down from its fiery creation, the sun was faint and young. So faint that it should not have been able to keep the oceans of earth from freezing. But fortunately for the creation of life, water was kept liquid on our young planet. Mars, methane and mysteries Mars may not be as dormant as scientists once thought. The 2004 discovery of methane means that either there is life on Mars, or that volcanic activity continues to generate heat below the martian surface. Surface features on Titan form like Earth's, but with a frigid twist "It is really surprising how closely Titan's surface resembles Earth's," says Rosaly Lopes, a planetary geologist at the Jet Propulsion Laboratory (JPL) in Pasadena, California, who is presenting the results on Friday, 7 August. New map hints at Venus's wet, volcanic past Venus Express has charted the first map of Venus's southern hemisphere at infrared wavelengths. The new map hints that our neighbouring world may once have been more Earth-like, with both, a plate tectonics system and an ocean of water. New definition could further limit habitable zones around distant suns As astronomers gaze toward nearby planetary systems in search of life, they are focusing their attention on each system's habitable zone, where heat radiated from the star is just right to keep a planet's water in liquid form. Magnetic Tornadoes Could Liberate Mercury's Tenuous Atmosphere As the closest planet to the sun, Mercury is scorching hot, with daytime temperatures of more than 800 degrees Fahrenheit (approximately 450 degrees Celsius). More Volcanic Activity Current Events and Volcanic Activity News Articles |
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