Chemistry in Space E-Book

Dieter Rehder

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 573

Veröffentlichungsjahr: 2011

Beschreibung

The dynamic field of extraterrestrial chemistry brings together ideas of chemistr, astrophysics, and biology to the study of molecules between stars, around stars, and on plantes. This book serves as an introduction to chemial processes under ?unearthly? and hence usually extreme conditions (temperature, pressure, high or low density, bombardment by cosmic rays), and their impact on the early development of our solar system, as well as providing a deeper understanding of processes in earthly regions where conditions approach those of extraterrestrial areas.
A unique and extraordinary perspective written with chemists in mind. An excellent practical book for inorganic, and physical chemists, spectroscopists, astronomers, and libraries.

From the contents:

* Introduction and technical notes
* Origin and development of the universe
* Stars
* The interstellar medium
* The solar system
* Exoplanets
* The origin of life

Leseprobe

Contents

Preface

1 Introduction and Technical Notes

2 Origin and Development of the Universe

2.1 The Big Bang

2.2 Cosmic Evolution: Dark Matter -the First Stars

2.3 Cosmo - Chronometry

3 The Evolution of Stars

3.1 Formation, Classification, and Evolution of Stars

3.2 Chemistry in AGB Stars

3.3 Galaxies and Clusters

4 The Interstellar Medium

4.1 General

4.2 Chemistry in Interstellar Clouds

5 The Solar System

5.1 Overview

5.2 Earth’s Moon and the Terrestrial Planets: Mercury, Venus, and Mars

5.3 Ceres, Asteroids, Meteorites, and Interplanetary Dust

5.4 Comets

5.5 Kuiper Belt Objects

5.6 The Giant Planets and Their Moons

6 Exoplanets

7 The Origin of Life

7.1 What is Life?

7.2 Putative Non-Carbon and Nonaqueous Life Forms; the Biological Role of Silicate, Phosphate, and Water

7.3 Life Under Extreme Conditions

7.4 Scenarios for the Primordial Supply of Basic Life Molecules

7.5 Extraterrestrial Life?

Index

The Author

Prof. Dr. Dieter Rehder

Universität Hamburg

Department Chemie

Martin-Luther-King-Platz 6

20146 Hamburg

Germany

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Cover

The molecules shown on the cover are formic acid and aminoacetonitrile. Both have recently been discovered in interstellar clouds.

Cover Design Grafik-Design Schulz, Fuβgönheim

Typesetting Toppan Best-set Premedia Limited, Hong Kong

Printing and Binding Fabulous Printers Pte Ltd

ISBN: 978-3-527-32689-1

Preface

On 27th December 1984, a team of "meteorite hunters," funded by the National Science Foundation, picked up a rock of 1.93 kg in an Antarctic area known as Alan Hills. Since it was the first one to be collected in 1984, it was labeled ALH84001, Alan Hills 1984 no. 001. Soon it became evident that this meteorite originated from our neighbor planet Mars-a rock that formed 4.1 billion years ago and was blasted off the red planet’s crust 15 million years ago by an impacting planetesimal. After roaming about in the Solar System for most of its time, this rock entered into the irresistible force of Earth’s attraction, where it landed 13 thousand years ago, in Antarctica and hence in an area where it was protected, at least in part, from weathering. Structural elements detected in this Martian meteorite, considered to represent biomarkers, sparked off a controversial debate on the possibility of early microbial life on our neighbor planet about 4 billion years ago, and shipping of Martian life forms to Earth, a debate which became reignited by recent reinvestigations of the meteoritic inclusions.

Other meteorites, originating from objects in the asteroid belt between Mars and Jupiter, have brought amino acids and nucleobases to Earth, among these amino acids which are essential for terrestrial life forms. Does this hint toward an extraterrestrial origin of at least part of the building blocks necessary for terrestrial life? And if yes - how could amino acids, which are rather complex molecules, have been synthesized and survived under conditions prevailing in space?

The idea of "seeds (spermata) of life," from which all organisms derive, goes back to the cosmological theory formulated by the Greek philosopher and mathematician Anaxagoras in the 5th century B.C. Anaxagoras, perhaps better known for his "squaring the circle," thus may be considered the originator of what became established as panspermia. Panspermia reached the level of a scientific (and popular) hypothesis in the 19th century through contributions from Berzelius, Pasteur, Richter, Thomson (Lord Kelvin), von Helmholtz, and others, a hypothesis according to which life originated and became distributed somewhere in space, and was transported to the planets from space. In 1903, the Swedish chemist Arrhenius proposed that radiation pressure exerted by stars such as our Sun can spread submicrometer to micrometer-sized "spores of life," a proposal that later (in the 1960s) was quantified by Sagan. The panspermia hypothesis got somewhat disreputable, when Francis H. Crick (who, together with Watson, received the 1962 Nobel Prize in Medicine for the discovery of the double -helix structure of desoxyribonucleic acid) and Leslie Orgel published a paper, in 1973, where they suggested that life arrived on Earth through "directed panspermia," where directed refers to an extraterrestrial civilization. The likeliness of another civilization somewhere else out in space is even more speculative than the likeliness that Life came into existence at all.

There is no doubt, of course, that life exists on Earth. Whether Earth is the cradle of life (from which it may have been transported elsewhere into our Solar System or even beyond) or whether life has been carried to our planet from outside (exospermia) remains an interesting concern to be addressed. ALH84001 may provide a clue to this question. The discovery of exoplanets (planets orbiting other stars than our Sun in the Milky Way galaxy) is another issue that stimulates imagination as it comes to the possibility of extraterrestrial life. New exoplanets are being discovered at a vertiginous speed, and a few of the about 455 exoplanets known to date, so-called super-Earths, do have features which are reminiscent of our planet.

Hamburg, May 2010

Dieter Rehder

3

The Evolution of Stars

In Section 2.2, the formation of the very first stars, the population III stars, has been addressed. These stars formed by accretion from minihalos predominantly containing dark matter (neutralinos) and the lightest of the elements, hydrogen (including its heavier isotope deuterium) and helium, plus traces of lithium and beryllium, produced in the first few minutes of the last episodes of the Big Bang event. In this chapter, the development of stars, emphasizing their chemical evolution, will be addressed, along with star clustering such as in globular clusters, open clusters, and galaxies. Clustering of stars is closely related to their formation and evolution. The basis for the rebirth of stars from the interstellar medium provided by evolving and dying stars will be described in Chapter 4.

3.1 Formation, Classification, and Evolution of Stars

3.1.1 General

As noted earlier, the first stars formed in our Universe shortly after the Big Bang. The particularly massive (about 106 Solar masses) population III stars would soon have perished in spectacular supernovae, dispersing their material throughout the Universe. From this material, the next generation of stars formed, the population II stars, for which low metallicities are characteristic. "Metallicity" in this context collectively refers to all elements heavier than He. Metallicity is commonly expressed in terms of the Fe/H ratio; iron is the most abundant metal in evolved stars. These old stars predominate in the bulge and the halo of galaxies, and also abound in globular clusters. Subsequent generations of stars were formed from interstellar gas clouds that had become enriched in metals manufactured by previous generations of stars. These young stars with high metallicities, population I stars, are abundant in the disc and the spiral arms of the galaxies. Our Sun is such a population I star.