How can we search for life on exoplanets? Step one: examine the Earth as if it were an exoplanet. That’s the idea behind a recent look at earthshine.
我们怎样寻找(太阳)系外行星上的生命?步骤一:把地球当做一个(太阳)系外行星进行研究。这是研究人员最近根据地球反照光想到的一个办法。
Researchers aimed what’s officially called the Very Large Telescope, housed at the European Southern Observatory, at the moon. They measured earthshine: sunlight that reflects off the Earth, hits the moon and bounces back.
研究人员通过设在欧洲南方天文台的超大望远镜观测了地球照射在月球的反照光。他们对地球的反照光进行了测量:太阳光被地球反射到月球,然后又反射回来。
The scientists are looking for hints of life in the light—such as evidence of the gases associated with organic life. Such gas signatures are generally tough to find, because any planetary light is swamped by the light of its host star.
科学家们在反射光中寻找生命的迹象——例如,寻找同有机生命相关的气体存在的证据。这种气体一般很难找到,因为任何行星的光线往往淹没在主星的光线中。
But in this effort, the research team also took into account polarized light. Because light reflected off a planet is polarized. But light from the star is not.
但通过这方面的努力,该研究小组还考虑到了偏振光的因素。因为行星的反照光往往会出现偏振,但恒星发出的光则不会如此。
The analysis of earthshine correctly revealed that the planet it came from has a partly cloudy atmosphere and is covered with oceans and some vegetation. The researchers could even ascertain changes in cloud cover and vegetation as the Earth turned. The research was published in the journal Nature.
对地球反照光的分析显示:这个行星拥有一个云雾大气层,还被海洋和一些植被所覆盖。研究人员甚至可以确定地球转动过程中的云层和植被所出现的变化。这项研究结果发表在《自然》杂志上。
Similar scrutiny of actual exoplanets may one day reveal the first good suspects for harboring life—via their light.
这种对系外行星反照光的类似分析也许有一天能够找到其它暗藏生命的行星。