一颗小行星明年1月可能撞上火星
美国宇航局12月21日发布的最新观测结果显示，一颗编号为2007 WD5的小行星明年1月末将穿越火星绕日轨道，估计它撞上火星的概率为1/75。天文学家正密切关注这颗小行星的运行轨迹。它现在位于地球和火星的中间地带，以每小时大约2.79万英里(1英里约合1.6公里)的速度向火星靠近。据估计它将于美国东部时间2008年1月30日6时(北京时间当天19时)左右，穿越火星的运行轨道。
目前，天文学家还不能计算出这颗小行星的精确运行轨道，只能估算出它和火星相撞的概率为1/75。
美国宇航局在其下属的喷气推进实验室设有一个“近地天体计划办公室”。据办公室介绍，这颗小行星于2007年11月20日首次被发现。由于它的轨道离地球比较近，还曾被列入“监视名单”。但后来的观测显示，这颗小行星对地球不构成威胁，反而有可能撞上火星。
喷气推进实验室科学家史蒂夫·切斯利介绍说，小行星撞火星大约每千年就会发生一次。近地天体计划办公室科学家唐·约曼斯说：“在未来的5个星期内，我们希望能收集到更多的观测信息，以进一步确定这颗小行星的轨道。” ::070821_17.jpg:: 为啥没人关注这事呢？ 等考完试再撞~::0023:: Updated Dec. 28, 2007 -- Astronomers have identified asteroid 2007 WD 5 in archival imagery. With these new observations, scientists at NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif have refined their trajectory estimates for the asteroid. Based on this latest analysis, the odds for the asteroid impacting Mars on Jan. 30 are now 1-in-25 -- or about 4 percent.
WASHINGTON - Astronomers funded by NASA are monitoring the trajectory of an asteroid estimated to be 50 meters (164 feet) wide that is expected to cross Mars' orbital path early next year. Observations provided by the astronomers and analyzed by NASA's Near-Earth Object Office at the Jet Propulsion Laboratory in Pasadena, Calif., indicate the object may pass within 30,000 miles of Mars at about 6 a.m. EST (3 a.m. PST) on Jan. 30, 2008.
"Right now asteroid 2007 WD5 is about half-way between Earth and Mars and closing the distance at a speed of about 27,900 miles per hour," said Don Yeomans, manager of the Near Earth Object Office at JPL. "Over the next five weeks, we hope to gather more information from observatories so we can further refine the asteroid's trajectory."
NASA detects and tracks asteroids and comets passing close to Earth. The Near Earth Object Observation Program, commonly called "Spaceguard," plots the orbits of these objects to determine if any could be potentially hazardous to our planet.
Asteroid 2007 WD5 was first discovered on Nov. 20, 2007, by the NASA-funded Catalina Sky Survey and put on a "watch list" because its orbit passes near Earth. Further observations from both the NASA-funded Spacewatch at Kitt Peak, Ariz., and the Magdalena Ridge Observatory in New Mexico gave scientists enough data to determine that the asteroid was not a danger to Earth, but could potentially impact Mars. This makes it a member of an interesting class of small objects that are both near Earth objects and "Mars crossers."
Because of current uncertainties about the asteroid's exact orbit, there is a 1-in-75 chance of 2007 WD5 impacting Mars. If this unlikely event were to occur, it would be somewhere within a broad swath across the planet north of where the Opportunity rover is located.
"We estimate such impacts occur on Mars every thousand years or so," said Steve Chesley, a scientist at JPL. "If 2007 WD5 were to thump Mars on Jan. 30, we calculate it would hit at about 30,000 miles per hour and might create a crater more than half-a-mile wide." The Mars Rover Opportunity is exploring a crater approximately this size right now.
Such a collision could release about three megatons of energy. Scientists believe an event of comparable magnitude occurred here on Earth in 1908 in Tunguska, Siberia, but no crater was created. The object was disintegrated by Earth's thicker atmosphere before it hit the ground, although the air blast devastated a large area of unpopulated forest.
大概意思就是说通过近期的观测，撞击率由原来的1.3%上升为4%，撞击位置接近于“机遇”号附近！
[ 本帖最后由 星林流水 于 2008-1-8 21:50 编辑 ] 原帖由 海星空 于 2007-12-28 16:06 发表 http://www.astronomy.com.cn/bbs/images/common/back.gif
为啥没人关注这事呢？
我也纳闷呢！可能是大家都在忙考试吧！
最初的文章在这儿，http://neo.jpl.nasa.gov/news/news151.html
看不太懂！谁能理解就看看去！ 为什么不撞地球来啊？::070821_17.jpg:: 现在几率已经掉到万分之一了
回复 7# 的帖子
想找陨石啊！不是外星人故意要砸的吧，呵呵。
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