对地球生命进化至关重要的糖首次在流星样本中被发现。
这一发现为假设增加了更多的分量，古代地球上的流星闪电战可以通过提供必要的构件来启动生命。
日本东北大学的古川义弘在2007年说:“以前在陨石中发现过其他重要的生命组成部分，包括氨基酸(蛋白质的成分)和核碱基(脱氧核糖核酸和核糖核酸的成分)，但是糖是生命组成部分中缺失的一部分。”声明。
发表于美国国家科学院学报研究人员说，(PNAS)揭示了生物学如何从非生物化学过程中产生的问题。这是因为在所研究的流星上发现的糖可能是地球上形成核糖核酸的首批例子中的关键成分。
研究人员能够使用气相色谱质谱技术在两块富含碳的陨石(穆尔奇森和西北非洲(NWA) 801)上鉴定糖，这是一个根据质量和电荷对分子进行分类的过程。
Murchison1969年降落在澳大利亚，而NWA 801降落在地球，2001年降落在非洲西北部。
该研究的主要作者古川说:“这项研究提供了核糖在太空中以及糖向地球输送的第一个直接证据。”。“外星糖可能促成了生命起源前地球上核糖核酸的形成。”
对流星粉末样品的分析表明核糖(核糖核酸中的一种关键成分)和其他类型的糖(包括阿拉伯糖和木糖)的含量各不相同——穆尔基森的含量最高为6.7-180份/十亿，NWA 801的含量最低为2.3-11份/十亿。
“在这种古老的材料中能够检测到像核糖一样脆弱的分子，这是很了不起的，”合著者杰森·德沃金说，他是美国宇航局太阳系探索部的副主任。
2019年8月2日，在一年一度的英仙座流星雨中，一块陨石在加利福尼亚州死谷附近的天然碱山顶上空。研究人员首次在陨石上发现了外星糖的证据。
相比之下，在研究的任何样本中，都没有2-脱氧核糖——制造脱氧核糖所需的糖——的证据，研究人员说这一结果支持了核糖核酸先于脱氧核糖核酸进化，后来被脱氧核糖核酸取代的观点。
“在这项研究分析的陨石中没有检测到脱氧核糖核酸中的糖，”美国宇航局太阳系探索部战略科学副主任丹尼·格拉文说。
“这一点很重要，因为可能存在外星核糖向早期地球传递的偏差，这与核糖核酸首先进化的假设是一致的。”
接下来，该团队计划研究更多陨石的化学成分。他们希望，这将使他们更好地了解外星糖有多常见和多易变。
SUGAR HAS BEEN DETECTED INSIDE METEORITES FOR THE FIRST TIME EVER
Sugars crucial to the evolution of life on Earth have been found in meteor samples for the first time.
The discovery adds more weight to the hypothesis a meteor blitz on ancient Earth could have kick-started life by providing the necessary building blocks.
"Other important building blocks of life have been found in meteorites previously, including amino acids (components of proteins) and nucleobases (components of DNA and RNA), but sugars have been a missing piece among the major building blocks of life," Yoshihiro Furukawa of Tohoku University, Japan, said in a statement.
A study published in Proceedings of the National Academy of Sciences of the United States of America (PNAS) sheds new light on the question of how biology arose from non-biological chemical processes, the researchers say. This being because the sugars discovered on the meteors studied may have been a key ingredient in some of the first examples of ribonucleic acid (RNA) formed on Earth.
Researchers were able to identify sugars on two carbon-rich meteorites (Murchison and North West Africa (NWA) 801) using gas chromatography mass spectrometry, a process that sorts molecules according to mass and electric charge.
Murchison fell to Earth and landed in Australia in 1969, while NWA 801 fell to Earth and landed in Northwest Africa in 2001.
"The research provides the first direct evidence of ribose in space and the delivery of the sugar to Earth," said Furukawa, lead author of the study. "The extraterrestrial sugar might have contributed to the formation of RNA on the prebiotic Earth which possibly led to the origin of life."
Analysis of powdered meteor samples showed levels of ribose (a critical ingredient in RNA) and other types of sugars, (including arabinose and xylose) varied—with a high of 6.7 to 180 parts per billion in Murchison and a low of 2.3 to 11 parts per billion in NWA 801.
"It is remarkable that a molecule as fragile as ribose could be detected in such ancient material," said co-author Jason Dworkin, Deputy Director of NASA's Solar System Exploration Division.
A meteorite overhead the Trona Pinnacles near Death Valley, CA during annual Perseid Meteor Showers, August 2, 2019. Researchers have found evidence of extraterrestrial sugars on meteorites for the first time.
In contrast, there was no evidence of 2-deoxyribose—the sugar required to make DNA—in any of the samples studied, a result the researchers say supports the idea RNA evolved prior to, and was later replaced by, DNA.
"The sugar in DNA (2-deoxyribose) was not detected in any of the meteorites analyzed in this study," said Danny Glavin, Associate Director for Strategic Science at NASA's Solar System Exploration Division.
"This is important since there could have been a delivery bias of extraterrestrial ribose to the early Earth which is consistent with the hypothesis that RNA evolved first."
Next up, the team plans to study the chemical composition of more meteorites. This, they hope, will enable them to gain a better idea of how common and how variable extraterrestrial sugars are.
