Chemical analysis of organic molecules in carbonaceous meteorites Torrao Pinto Martins, Zita Carla Citation Torrao Pinto Martins, Z. C. (2007, January 24). Chemical analysis of organic molecules in carbonaceous meteorites. Retrieved from https://hdl.handle.net/1887/9450 Version: Corrected Publisher’s Version Licence agreement concerning inclusion of doctoral License: thesis in the Institutional Repository of the University of Leiden Downloaded from: https://hdl.handle.net/1887/9450 Note: To cite this publication please use the final published version (if applicable). ______________________________________________________ CHAPTER 1 ______________________________________________________ Introduction 1.1 Heavenly stones-from myth to science Ancient chronicles, from the Egyptian, Chinese, Greek, Roman and Sumerian civilizations documented the fall1 of meteorites, with Sumerian texts from around the end of the third millennium B. C. describing possibly one of the earliest words for meteoritic iron (Fig. 1.1 Left). Egyptian hieroglyphs meaning “heavenly iron” (Fig. 1.1 Right) found in pyramids together with the use of meteoritic iron in jewellery and artefacts show the importance of meteorites in early Egypt. Meteorites were worshiped by ancient Greeks and Romans, who struck coins to celebrate their fall, with the cult to worship meteorites prevailing for many centuries. For example, some American Indian tribes paid tribute to large iron meteorites, and even in modern days the Black Stone of the Ka´bah in Mecca is worshiped and regarded by Muslims as “an object from heaven”. The oldest preserved meteorite that was observed to fall (19th May 861) was found recently (October 1979) in a Shinto temple in Nogata, Japan. It weighted 472 g and it was stored in a wooden box. The second oldest observed fall from which the meteorite is still preserved occurred in Ensisheim in Alsace, France (at that time it was part of Germany) on the 7th November 1492, just before noon (Fig. 1.2). Soon after, the town people gathered around the place where the meteorite was lying and started chipping off pieces, thinking these were good luck charms, until stopped by the town magistrate. The meteorite was then carried into the city and placed in front of the church door. A few weeks later, the German King Maximilian travelled through the city of Ensisheim, and after examining the meteorite declared it as divine and a sign of his victory against the French enemy. The King ordered the meteorite to be preserved in the church as a reminder of the intervention from God. After the meteorite was placed inside the church, the following inscription was written next to it: “Many know about it, each know something, but no one knows enough”. The meteorite stayed there until the French Revolution, when it was moved to Colmar (France) in 1793 and fragments were taken for analysis. Years later, a 56 kg specimen of the meteorite returned to Ensisheim, being exhibited until today in the town hall. ______________________________ 1”Falls” are recovered meteorites that were observed to fall, while “finds” are recovered meteorites that were not seen to fall. 1 Chapter 1 Fig. 1.1 – (Left) The Sumerian symbol Kù-an may represent the earliest word for meteoritic iron. (Right) The hieroglyph bith, meaning heavenly iron, was found in Egyptian pyramids. Taken from Bevan and de Laeter (2002). Despite reports of meteorite falls like the one in Ensisheim, for centuries there was no scientific explanation for the “stones falling from heaven”. During the time of the Greek philosopher Aristotle (384-322 B.C.) meteorites were thought to be atmospheric phenomena. In fact, the word meteorite comes from the ancient Greek word meteoros or meteora, which means “things lifted in the air”. Aristotle thought that rocks could not fall from the sky because the heavens represented the celestial perfection. In order to explain the fall of a meteorite at Thrace near Aegospotami, Aristotle concluded that strong winds had lifted a rock formed on Earth into the atmosphere, and then dropped it again! His view was shared for many centuries. Scientific progress was extremely slow over the following centuries. The next significant step toward the understanding of the solar system came toward the end of the sixteenth century. The work of the astronomer Copernicus (1473-1543), published in 1543, replaced the Earth (geocentric theory) by the Sun (heliocentric theory) as the centre of the solar system. The first evidence for Copernicus’s heliocentric theory was provided by observations of the phases of Venus and the moons of Jupiter by the Italian astronomer Galileo (1564-1642). Additional evidence of a heliocentric model was presented by the German mathematician and astronomer Johannes Kepler (1571-1630), who deduced empirical laws of planetary motion, describing planetary orbits around the Sun. The English physicist and mathematician Isaac Newton (1643-1727) introduced the concept of gravity (through his theory of Universal Gravitation), which allowed the determination of the orbits of planets and comets. By the eighteenth century scientists had a more rational view of the world, due to the influence of Enlightenment that aimed to find the truth via objective means. Many scientists refused the idea that stones could fall from the sky, with some scientists simply denying the existence of meteorites. Soon a new era would start with the work by German physicist Ernst Chladni (1756-1827). In 1794 he published a 63-page book entitled Über den Ursprung der von Pallas gefundenen und anderer ihr änlicher Eisenmassen und über einige damit in Verbindung stehende Naturerscheinungen (On the origin of the mass of iron found by Pallas and of other similar iron masses, and on a few natural phenomena connected therewith). In his book, Ernst Chladni described the stony-iron meteorite Pallas (that was found in Siberia in 1749) and four iron meteorites, based only on reports of fireballs and falling meteorites. He suggested that stones and iron meteorites fell from the sky and originated from cosmic space. Chladni additionally 2 Chemical analysis of organic molecules in carbonaceous meteorites Fig. 1.2 - Drawing of the Ensisheim meteorite fall (1492) showing the meteorite in the air and in the wheat fields outside the city, which gives the idea of movement. Taken from http://ares.jsc.nasa.gov/Education/Activities/ExpMetMys/Lesson15.pdf. speculated that under the influence of Earth’s gravitational force meteorites could be the observed fireballs, as friction with the terrestrial atmosphere would heat them and produce an incandescent glow. Although remarkable, especially because they were only based in few evidences, the ideas of Ernst Chladni were not accepted by the scientific community of that time. In that same year, on the 19th June 1794, a shower of stones fell at Siena (Italy). It was witnessed by such a large number of people, that its authenticity could not be denied. The simultaneous eruption of Mt Vesuvius raised the question about whether there was a possible link between these stones and volcanic activity. During the course of that year the Siena fall was documented by two eminent Italian scholars, and by the English Ambassador in Naples, Sir William Hamilton who reported simultaneously on the Siena fall and the eruption of Mt. Vesuvius, his reports being published by the Royal Society. All these accounts led to the scientific debate around Europe about the origin of the fallen stones. Subsequent reports of meteorite falls at the World Cottage (England) in 1795, in Belaya Tserkov (Russia) and Évora (Portugal) in 1796, Salles (France) and Benares (India) in 1798, led the president of the Royal Society, Sir Joseph Banks, to think that it was time to perform a serious study on this subject. Sir Joseph Banks gave samples of the Siena and World Cottage stones to the English chemist Edward C. Howard (1774-1816). He collected two more stones and four “native irons” (which according to Ernst Chladni must have fallen from the sky), and analysed them, together with the French mineralogist Jacques-Louis de Bournon (1751-1825). Bournon separated each stone into its main components, including grains of metal. In 1802, Howard showed not only similarities between the chemical composition of the four stones, but also a significant quantity of nickel (a metal that is rare in iron ores on Earth) in each of the irons and in the metal grains of the stones. This established for the first time not only a link between stony and iron meteorites that had fallen at different times and locations on Earth, but also strongly implied an origin outside the Earth. The work of Howard and Bournon rapidly convinced scientists that indeed meteorites fell from the sky, but also that they had an extraterrestrial origin. The few remaining sceptics were finally convinced by the carefully written paper of the renowned French scientist Jean-Baptiste 3 Chapter 1 Biot (1774-1862), who was commissioned by the French Minister of the Interior to investigate the fall of about three thousand stones in L’Aigle (France) on the 26th April 1803. Ernst Chladni received full credit for his hypothesis that meteorites fell from the sky. However, it took decades until his hypothesis of linking falling bodies with fireballs was generally accepted. Until about 1860, possible origins of meteorites included condensation within the atmosphere and eruptions from lunar volcanoes. Most astronomers of the time supported the latter idea. In fact, the German-born British astronomer William Herschel (1738- 1822) reported in 1787 to have observed active volcanoes on the Moon. Ernst Chladni believed that meteorites originated from cosmic space, because of the high apparent velocities of meteorites and fireballs. However, in 1805 he accepted a probable lunar origin based on the fact that all the meteorites analysed showed no oxidation and also due to the agreement between the average density of the meteorites with calculations of the density of the Moon.