在古代隕石中發(fā)現(xiàn)的外星糖

在古代隕石中發(fā)現(xiàn)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.

一個由科學家組成的國際研究小組分析了在地球上發(fā)現(xiàn)的古代隕石碎片，發(fā)現(xiàn)了對生命形成至關重要的外星糖類。

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).

在一項發(fā)表在《美國國家科學院院刊》上的研究中，研究人員揭示了他們?nèi)绾问褂脷庀嗌V-質(zhì)譜法分析兩塊隕石粉末樣品的化學性質(zhì)。隨后的報告詳細介紹了大量的生物必需糖，如阿拉伯糖、木糖和核糖;后者是RNA的重要組成部分(核糖核酸)。

Life finds a way

生活總有辦法

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.

關于地球上的生命是如何進化的，有一種理論源于所謂的“晚期重轟擊”，這段時間可以追溯到41億到38億年前，當時太陽系內(nèi)部密集地擠滿了小行星。結(jié)果，這些漫游的天體與水星、金星、地球和火星等類地行星之間發(fā)生了不成比例的大量碰撞。這一時期的撞擊是如此劇烈，多達22000個直徑超過12英里的隕石坑給地球年輕的表面留下了累累傷痕。

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，從這個暴力的開始，生命的種子可能已經(jīng)被播種。一些研究人員認為，攜帶遺傳信息的RNA首先在地球上進化，后來被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.

對于那些想知道隕石糖是否在地球上被污染的人，研究人員也有答案。

"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."

他們寫道:“地球上的生命更喜歡使用較輕的碳(12C)，而不是較重的碳(13C)。”“然而，重13C的隕石糖中碳含量顯著增加，超過了地球生物中碳含量，支持了碳來自太空的結(jié)論。”

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.

接下來，研究小組計劃研究更多的隕石，以測量這些外星糖的豐度。他們還熱切地期待著分析日本和美國的宇宙飛船最近從原始小行星琉球和本奴收集到的原始樣本。生物必需糖在宇宙中有多豐富?當這些樣本分別在2020年末和2023年返回地球時，我們會發(fā)現(xiàn)更多。