新概念英语：火星上有“树”原是视错觉(图)

人类探索外星生命的脚步从来没有停止过，而我们的近邻火星就是重点观测对象之一。日前，美国国家航空航天局NASA就从环火星卫星上获得一张照片，照片中清楚的显示火星地表有树木生长！这是真的吗？

Nasa photographs 'trees' on Mars

美国国家航空航天局从火星上拍到“树木”

The images appear to show rows of dark "conifers" sprouting from dunes and hills on the planet surface. But the scene is actually an optical illusion。

从图片中我们可以看出，成排的“针叶林”从火星表面的沙丘和小山上长出。而事实上，这样的场景只是一种光学错觉。

The photographs actually show sand dunes coated with a thin layer of frozen carbon dioxide, or dry ice, less than 240 miles from the planet's north pole。

这张图片实际显示的，是距离火星北极不足240英里的沙丘上覆盖的一层薄薄的冰冻二氧化碳、或干冰。

The "trees" are really trails of debris caused by landslides as ice melts in Mars's spring. You can even see a cloud of dust, just to the left of centre of the picture, where an avalanche is caught happening。

这些“树木”的真实面孔是火星春天冰层融化时造成山崩、从而产生的碎片痕迹。你甚至可以从图片正中偏左的位置上、看到一场被抓拍到的雪崩，那里有一团尘雾。

The photograph was taken from orbit around Mars by HiRISE, the most powerful camera sent to another planet。

这张图片是由环绕火星轨道卫星上的HiRISE拍到，这是我们派往火星最强大的照相机。

NASA's Candy Hansen told The Sun: "The streaks are sand, dislodged as ice evaporates, which slide down the dune. At this time of the Martian year the whole scene is covered by CO2 frost."

美国国家航空航天局的Candy Hansen告诉记者：“这些纹路是沙子，在冰层蒸发的时候发生了位置偏移，从而滑下了沙丘。在火星的这个季节里，整个星球都被二氧化碳的迷雾覆盖。”

Last month Nasa announced a new telescope had detected five planets outside the solar system. The observatory, which was launched last year to find other Earths, made the discoveries in its first few weeks of science operations。

上个月，美国国家航空航天局宣布他们的新望远镜发现了太阳系外的五个星球。该观测台去年在刚开始科学探测的几个星期内，就曾宣布他们发现了另一个地球

Although the new worlds, called exoplanets, are all bigger than Neptune, Nasa said their discovery showed that the planet hunting telescope was working well。

尽管这些被发现的新外部行星都比海王星要大，美国国家航空航天局仍表示，他们的望远镜在探测行星时运行良好。