一项开创性研究称，关于彗星将生命构建基石带到地球的百年理论可能完全错误。
A century-old theory that comets brought the building blocks of life to Earth may be completely wrong, according to a groundbreaking study.
科学家长期以来一直认为，彗星——这些装满含碳和含氮分子的巨型冰质太空岩石——持续向地球输送了播种生命所需的前生物分子。
Scientists have long believed that comets — giant icy space rocks packed with carbon- and nitrogen-bearing molecules — delivered a steady rain of prebiotics needed to seed life on Earth.
但剑桥大学的研究人员发现，根据上周发表在《科学报告》上的研究，这些生命构建前生物分子在彗星与地球高速撞击中存活下来的可能性实际上很小。
But researchers at the University of Cambridge found that the chances of those life-building prebiotic molecules surviving a comet’s high-speed impact with Earth are actually slim, according to the study published in Scientific Reports last week.
“历史上，科学家认为彗星对地球生命起源很重要，因为它们携带含碳和含氮分子，所以这些巨型太空雪球几乎就像一张‘免死金牌’，带来了行星播种生命所需的所有分子，”该研究的主要作者、剑桥大学天文学院的理查德·安斯洛博士在一份声明中说。
“Historically, scientists thought that comets were important for the origin of life on Earth, because they carried carbon- and nitrogen-bearing molecules, so these giant space snowballs were almost like a ‘get out of jail free card’ that brought all the molecules a planet would need to seed life,” lead author Dr Richard Anslow from Cambridge’s Institute of Astronomy said in a statement.
“这是一种挺浪漫的想法，但我们的结果表明，这极不可能，”安斯洛说。
“It’s kind of a romantic idea, but our results suggest it’s highly unlikely,” Anslow said.
研究人员说，彗星通常速度太快，撞击角度也太陡，导致分子汽化。
Comets typically travel too fast and strike at too sharp an angle, causing the molecules to vaporize, researchers said.
但即使有些构建基石在“一次偶然事件”中存活下来，其浓度可能也不足以产生生命。
But even if some building blocks survived in a “one-off fluke,” there may not be a concentration high enough to create life.
“这真的必须是百万分之一的事件，因为你不仅需要撞击速度恰到好处、角度恰到好处，还需要在那之后发生一切，包括浓度以及生命化学起源的速度，”安斯洛说。
“It would really have to be a one-in-a-million occurrence, because not only would you need an impact at just the right speed and just the right angle, you would also need everything to happen after that point, in terms of the concentration and the speed at which the chemical origins of life got going,” said Anslow.
“我们不能百分之百排除它是那样发生的。但这似乎是一种非常罕见的事件——至多，是一次偶然事件。”研究人员说，生命的分子种子可能来自其他几个地方，例如小行星，小行星撞击地球的频率远高于彗星。
“We can’t rule out for certain that it happened that way. But it seems to be a really rare occurrence – at best, a one-off fluke.”Researchers said the molecular seeds of life could have come from several other places, such as asteroids, which hit Earth far more frequently.
虽然彗星将生命构建分子送到地球似乎不太可能，但科学家发现，太阳系中的邻近行星可能更适宜居住。
Although cometary delivery of life-building molecules on Earth seems unlikely, scientists found that our neighbors in the solar system may be more habitable.
彗星更有可能到达火星表面，因为火星比地球小，大气层更稀薄，尤其是在太阳系早期发展阶段，当时这类太空岩石更为常见。
Comets would be more likely to make it on the surface of Mars, which is smaller than Earth and has a thinner atmosphere, especially during the period of the solar system’s development when the space rocks were more common.
“当然，这并不意味着这件事在火星上肯定发生过，但这表明，如果它在地球上发生了而在火星上没有发生，那将不太可能，”安斯洛说。
“This is not to say it definitely happened on Mars, of course, but suggests it would be unlikely if it happened on Earth and didn’t happen on Mars,” Anslow said.
“或者，也许更可能的另一种选择是，这两颗行星都没有发生过。”
“Or the other, perhaps more likely, alternative is that it didn’t happen on either planet.”