隕石內有機物質之統計研究

Abstract

據目前所知，地球是宇宙中獨有的生命孕育之處，但我們對於生命的起源卻不甚了解。先前的研究顯示，地球生命中的一些有機分子，也存在於數個最原始的隕石種類中。因此，這些有機分子可能伴隨隕石抵達地球，成為生命最初的組成。在本研究中，作者以創新的方法研究隕石內有機體的性質。不同於傳統的圖像分析，作者使用NanoSIMS儀器測繪SaU 290隕石的表面圖，並使用SourceExtractor軟體分析影像，以統計方法研究超過五千項有機物的形態學性質、元素組成與同位素組成。作者藉由反覆且全面地測試分析結果、進行數據過濾，最佳化統計結果的正確性，並將分析數據與先前研究已繪製出的Murchison、GRA 95229、QUE 99177隕石圖相較，得出研究結果。此份結果為隕石內有機體性質提供了許多新的資訊；包括不同隕石內有機體的形態學、元素、同位素變數的相關性，特定種類的有機體容易群聚的傾向，以及研究中四種隕石的特性。有鑑於太陽系演化的複雜性以及隕石中有機物的多樣性，作者認為，本研究結果中不同隕石內有機物的相關和趨勢，可為生命起源提供嶄新的見解。

At present, Earth is the only place that is known to harbour life in this Universe, and little is understood about the origin of life. Previous laboratory studies discovered that some of the organic molecules that reside in life on Earth also occur in the most primitive types of meteorites. As such, they may have contributed to building blocks of life through extraterrestrial delivery. In this thesis, we discuss our novel approach for studying the nature of meteoritic organics. Instead of the conventional image-by-image analysis, we used our NanoSIMS to map a large surface area of SaU 290 and studied the statistical behaviour of over 5,000 organic inclusions, which were automatically extracted by image analysis software (SourceExtractor). We extensively tested all parts of our analysis and performed data filtering, to maximise the accuracy of the obtained data on SaU290. The data was compared with the previously recorded maps of three other meteorites: Murchison, GRA 95229 and QUE 99177. As a result, we acquired a large set of new information on the nature of meteoritic organics, including correlations among the morphological, elemental and isotopic parameters of each meteorite, tendencies for certain types of organic inclusions to cluster, and trends among the four meteorites. Given the complex evolution of the Solar System and the diversity of meteoritic organics, we conclude that the correlations and the trends that were found within and among the meteorites in this study offer new insights to the current understanding of the origin of life.