The gravitational tug of large planets,like Jupiter and Saturn, could sling some planets on "escapetrajectories", propelling them off beyond their solar system into theempty space between stars.

木星和土星等大行星的引力拖曳, 可把某些行星抛掷到“逃逸轨迹上”，把它们推出其自身的太阳系外，进入空旷的星际空间。

That might seem to consign them to a coldand barren future. But some scientists believe that the first life on Earth wasnot powered by sunlight, but by volcanic energy released from the planet'sinterior at hot vents in the deep sea.

这看起来似乎是把它们交付给了一个寒冷而荒芜的未来。但一些科学家认为，地球上最初的生命并不是由太阳提供能量的，而是由深海热液喷口喷出的地球内部释放的火山能量驱动的。

All of the rocky planets in the inner solarsystem come with two internal heat sources.

太阳系的所有岩态行星都有两个内部热源。

First, each planet has a fiery core stillhot from the primordial fury of its formation. On top of that, they containradioactive elements. Primordial heat and radioactive decay inside rocky rogueplanets could warm them for billions of years – perhaps enough to keep theplanets volcanically active and provide the energy for life to start.

第一，每个行星都有炙热核心，仍然保持着形成过程中的原始狂暴产生的热量。除此之外，它们还含有放射性元素。岩态的流浪行星内部的原始热能和放射性衰变，可温暖它们数十亿年– 也许足够保持行星上的火山活跃，为生命的开始提供能量。

Rogue planets could also have dense,heat-retaining atmospheres. Compared with gas giants like Jupiter and Saturn,Earth's atmosphere is thin and tenuous, because the Sun's heat and light havestripped away lighter gases like hydrogen. Mercury is so close to the Sun thatit barely has any atmosphere at all.

流浪行星还可有稠密储热的大气层。与木星和土星等气态巨星相比，地球的大气层稀薄，因为太阳的热和光除去了氢气等较轻的气体。水星离太阳如此之近，以致几乎没有任何大气层。

Yet on an Earth-sized rogue planet, farbeyond its parent star's influence, much of the original atmosphere mightremain in place. The resulting temperature and pressure could be enough tosustain liquid water at the surface, even without any sunlight.

然而在地球大小的流浪行星上，因为远离母恒星的影响，原始大气层可能大体保持了原样。由此产生的气温和压力可能足以在星球表面维持液态水，即使没有任何阳光。

What's more, rogue planets would not beplagued by giant meteorite impacts, as Earth has been.

而且，流浪行星不会受到巨陨石撞击的困扰，像地球曾经遭受的那样。

If these ideas are right, then outside oursolar system rogue planets in interstellar space could be the closest placeswhere extraterrestrial life exists.

若这些想法对头，那么在我们的太阳系外，星际空间的流浪行星可能是离我们最近的外星生命存在的地方。