在古代陨石中发现的外星糖

An international team of scientists analyzing fragments of ancient meteorites recovered on Earth has made the remarkable discovery of extraterrestrial sugars vital to the formation of life.

一个由科学家组成的国际研究小组分析了在地球上发现的古代陨石碎片，发现了对生命形成至关重要的外星糖类。

An illustration of meteors streaking through the Earth's atmosphere. (Photo: By Vadim Sadovski/Shutterstock)

In a study, published in the Proceedings of the National Academy of Sciences, the researchers reveal how they used gas chromatography mass spectrometry to analyze the chemical nature of powdered samples of two meteorites. The subsequent report detailed an abundance of bio-essential sugars such as arabinose, xylose and ribose; with the latter a vital component of RNA (Ribonucleic acid).

在一项发表在《美国国家科学院院刊》上的研究中，研究人员揭示了他们如何使用气相色谱-质谱法分析两块陨石粉末样品的化学性质。随后的报告详细介绍了大量的生物必需糖，如阿拉伯糖、木糖和核糖;后者是RNA的重要组成部分(核糖核酸)。

Life finds a way

生活总有办法

This is a model of the molecular structure of ribose and an image of the Murchison meteorite. Ribose and other sugars were found in this meteorite. (Photo: Yoshihiro Furukawa/NASA)

One theory for how life evolved on Earth stems from what's known as the "Late Heavy Bombardment," a period of time dating back 4.1 to 3.8 billion years ago when the inner solar system was densely packed with asteroids. As a result, a disproportionately large number of collisions took place between these wandering bodies and the terrestrial planets of Mercury, Venus, Earth and Mars. This period of bombardment was so cataclysmic, that as many as 22,000 impact craters with diameters in excess of 12 miles may have scarred Earth's young surface.

关于地球上的生命是如何进化的，有一种理论源于所谓的“晚期重轰击”，这段时间可以追溯到41亿到38亿年前，当时太阳系内部密集地挤满了小行星。结果，这些漫游的天体与水星、金星、地球和火星等类地行星之间发生了不成比例的大量碰撞。这一时期的撞击是如此剧烈，多达22000个直径超过12英里的陨石坑给地球年轻的表面留下了累累伤痕。

From this violent beginning, however, the seeds of life may have first been planted. Some researchers believe that RNA, which carries genetic information, evolved first on Earth and was later replaced by DNA.

然而，从这个暴力的开始，生命的种子可能已经被播种。一些研究人员认为，携带遗传信息的RNA首先在地球上进化，后来被DNA取代。

For those wondering if the meteorite sugars may have become contaminated in their time on Earth, the researchers have an answer there as well.

对于那些想知道陨石糖是否在地球上被污染的人，研究人员也有答案。

"Life on Earth prefers to use the lighter variety of carbon (12C) over the heavier version (13C)," they write. "However, the carbon in the meteorite sugars was significantly enriched in the heavy 13C, beyond the amount seen in terrestrial biology, supporting the conclusion that it came from space."

他们写道:“地球上的生命更喜欢使用较轻的碳(12C)，而不是较重的碳(13C)。”“然而，重13C的陨石糖中碳含量显著增加，超过了地球生物中碳含量，支持了碳来自太空的结论。”

Moving forward, the research teams plans on studying more meteorites to gauge the abundance of these the extraterrestrial sugars. They're also eagerly looking forward to analyzing pristine samples recently collected from primitive asteroids Ryugu and Bennu by Japanese and American spacecraft. How abundant are bio-essential sugars in the universe? We'll find out more when the samples return to Earth in late 2020 and 2023 respectively.

接下来，研究小组计划研究更多的陨石，以测量这些外星糖的丰度。他们还热切地期待着分析日本和美国的宇宙飞船最近从原始小行星琉球和本奴收集到的原始样本。生物必需糖在宇宙中有多丰富?当这些样本分别在2020年末和2023年返回地球时，我们会发现更多。