Extraterrestrial Amino Acids in Cretaceous-Tertiary BoundarySediments

白垩纪-第三纪边界沉积物中的地外氨基酸

• 批准号: 8915829
• 负责人: Joseph Baird
• 金额: $ 9.98万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-01-15 至 1992-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8915829&HistoricalAwards=false
• 关键词: Extraterrestrial; Amino; Acids; Cretaceous; Tertiary

The report that Cretaceous/Tertiary (K/T) boundary sediments are greatly enriched in iridium (Ir) has generated an intense controversy concerning the origin of this signal. Although convincing evidence suggests that the Ir anomaly was generated by the collision of a large bolide with the Earth, other explanations claim that extensive, violent volcanism can account for the Ir spike. We have recently found that K/T boundary sediments at Stevns Klint, Denmark contain two amino acids which are exceedingly rare on the Earth, but which are some of the most abundant amino acids in carbonaceous meteorites. An extraterrestrial source is the most reasonable explanation for the presence of these amino acids. Many questions have been raised by our preliminary study. Are these extraterrestrial amino acids present in other K/T boundary sediments? How do we explain the large amounts of extraterrestrial amino acids in the K/T boundary sediments? Why is the extraterrestrial amino acid signal absent in the Stevns Klint boundary clay, but present directly above and below? In order to answer these questions we will examine other K/T boundary sequences for amino acids; stable isotope analyses will be performed on the isolated amino acid fractions to further demonstrate their extraterrestrial origin; sediments of different ages and depositional environments will be analyzed to determine whether there is a measurable terrestrial production of these amino acids; we will investigate whether other extraterrestrial amino acids are present in K/T boundary sediments; and experiments will be conducted to evaluate the survivability of extraterrestrial amino acids both during impact and after deposition. These analyses will enable us to ascertain the global distribution of the extraterrestrial amino acid signal, what processes may have subsequently disturbed these amino acids, and what kind of object or processes supplied this unique organic cosmochemical signal.

有关白垩纪/第三纪（K/T）界线沉积物中铱（Ir）富集的报道引起了关于该信号来源的激烈争论。虽然令人信服的证据表明，Ir异常是由一个大的火流星与地球碰撞产生的，但其他的解释声称，广泛的、剧烈的火山活动可以解释Ir峰值。我们最近在丹麦的Stevns Klint发现K/T边界沉积物中含有两种氨基酸，这两种氨基酸在地球上极为罕见，但却是碳质陨石中最丰富的氨基酸。对于这些氨基酸的存在，外星来源是最合理的解释。我们的初步研究提出了许多问题。这些外星氨基酸是否存在于其他K/T边界沉积物中？我们如何解释K/T边界沉积物中大量的外星氨基酸？为什么外星氨基酸信号没有出现在史蒂文斯·克林特边界粘土中，而直接出现在上面和下面？为了回答这些问题，我们将研究氨基酸的其他K/T边界序列；将对分离的氨基酸组分进行稳定同位素分析，以进一步证明它们的外星来源；将分析不同年龄和沉积环境的沉积物，以确定是否存在可测量的这些氨基酸的陆地生产；我们将研究在K/T边界沉积物中是否存在其他地外氨基酸；并将进行实验来评估外星氨基酸在撞击期间和沉积后的生存能力。这些分析将使我们能够确定地外氨基酸信号的全球分布，哪些过程可能随后干扰了这些氨基酸，以及什么样的物体或过程提供了这种独特的有机宇宙化学信号。