60秒科学:美宇航局发现前苏联遗留在月球的激光（在线收听）

据《科学》杂志报道，苏联的月球车40年前在月球表面留下了激光反射器，虽然经过多年的搜寻科学家始终没有发现激光反射器的踪迹。

　　4月22日，一组物理学家终于发现了来自反射器的微弱闪光。NASA的月球侦察轨道器在这项发现中起了重要作用，它上个月拍摄了据报导苏联登月车驶过的地区的卫星图像。加州大学圣迭戈分校的Tom Murphy领导的团队分析了地图，终于发现了反射器的位置。利用新墨西哥州Apache Point天文台3.5米口径望远镜发射出的一束激光，研究人员立即测量出地球到反射器的距离，误差在1厘米内。

In 1970 the Soviet Union put a laser reflector on the moon, carried by a rover. A few months later, it disappeared. Some speculated that the rover had fallen into a crater or parked in such a way as to render the reflector inaccessible. Now, after 40 years on the lunar surface, the reflector has been found.

A team at U.C. San Diego had been searching for it. Earlier this year, NASA’s Lunar Reconnaissance Orbiter camera provided images of the original landing area. A sunlit speck, miles from where the team was looking, turned out to be the rover and reflector. The San Diego team was quickly able to pinpoint the reflector’s location to within 10 meters.

Scientists send laser pulses to the moon and measure signals that bounce back from three reflectors left by Apollo astronauts, along with another Soviet one. This information helps track the moon’s position and orbit. And the researchers say that the rediscovered Russian reflector is particularly useful for studying the moon’s liquid core and testing ideas about gravity. Says team leader Tom Murphy of the reflector, “It’s got a lot to say after almost 40 years of silence.”