Comets And Their Origin E-Book

Uwe Meierhenrich

• Herausgeber: Wiley-VCH
• Kategorie: Lebensstil
• Sprache: Englisch
• Veröffentlichungsjahr: 2014

Seitenzahl: 740

Beschreibung

Divided into two parts, the first four chapters of Comets And Their Origin refer to comets and their formation in general, describing cometary missions, comet remote observations, astrochemistry, artificial comets, and the chirality phenomenon. The second part covers the cometary ROSETTA mission, its launch, journey, scientific objectives, and instrumentations, as well as the landing scenario on a cometary nucleus. Along the way, the author presents general questions concerning the origin of terrestrial water and the molecular beginnings of life on Earth, as well as how the instruments used on a space mission like ROSETTA can help answer them. The text concludes with a chapter on what scientists expect from the ROSETTA mission and how its data will influence our life on Earth. As a result, the author elucidates highly topical and fascinating knowledge to scientists and students of various scientific backgrounds, allowing them to work with ROSETTA's data.

Leseprobe

Table of Contents

Cover

Related Titles

Title Page

Copyright

Dedication

Foreword by Michael F. A'Hearn

Foreword by Gerhard H. Schwehm

Preface

List of Abbreviations and Symbols

Part I: Comets and their Origin

Chapter 1: Introduction

1.1 Preliminary Remarks

1.2 Motivation to Land a Probe on a Cometary Nucleus

1.3 Introduction to the Physical Characteristics of Comets

1.4 Space Probes Vega, Sakigake, and Suisei: Observations of Comet 1P/Halley

1.5 The Giotto Spacecraft and the First Image of a Cometary Nucleus

1.6 Comet 19P/Borrelly as Observed by Deep Space 1 and the Contour Comet Nucleus Tour

1.7 The Stardust Sample Return Mission to Comet 81P/Wild

1.8 The Deep Impact Mission's Excavation of Comet 9P/Tempel 1

References

Chapter 2: The Formation of Comets

2.1 Introduction

2.2 Whipple's Dirty Snowball Model of Cometary Nuclei

2.3 Formation and Collection of Interplanetary Dust Particles or Brownlee Particles

2.4 The Greenberg Core-Mantle Grain Model

2.5 Remote Photometric and Spectroscopic Characterization of Comets

References

Chapter 3: Astrochemistry: Water and Organic Molecules in Comets

3.1 Water in Cometary Ices

3.2 Artificial Comets: Organic Molecules Identified in Simulated Interstellar Ices

3.3 Amino Acids in Simulated Interstellar Ices

3.4 The Intended Detection of Organic Molecules in a Cometary Nucleus

3.5 The Behavior of Organic Molecules During Cometary Impact

3.6 The Origin of Life on Earth

References

Chapter 4: The Asymmetry of Life

4.1 Introduction

4.2 The Photochemical Formation of Chiral Organic Molecules

4.3 Enantiomeric Excesses in Meteoritic Molecules

4.4 Symmetry Breaking by the Weak Nuclear Interaction

4.5 Enantioselective Instruments on the Mars Science Laboratory and ExoMars

References

Part II: The Rosetta Mission-Rendezvous with a Comet

Chapter 5: The Rosetta Cometary Mission: Launch and Target Comet

5.1 Introduction

5.2 Launch Countdown in 2002 and the Targeting of Comet 46P/Wirtanen

5.3 The Successful Rosetta Launch with an Ariane 5G+ Rocket in 2004

5.4 Characterization of Target Comet 67P/Churyumov-Gerasimenko

References

Chapter 6: On the Way to Comet 67P/Churyumov-Gerasimenko

6.1 Accelerating the Rosetta Probe Using Swing-by Maneuvers Around Mars and Earth

6.2 Rosetta's Observation of Comet 9P/Tempel during the Deep Impact Event in 2005

6.3 Rosetta Spacecraft Mistaken as a Near-Earth Asteroid

6.4 Rosetta's Asteroid Flybys: Šteins in 2008 and Lutetia in 2010

6.5 Rosetta Operations Prior to the Cometary Rendezvous

References

Chapter 7: Rosetta's Rendezvous with the Comet

7.1 Introduction

7.2 Rosetta in an Artificial Orbit Around the Comet

7.3 Soft-landing on the Nucleus of Comet 67P/Churyumov-Gerasimenko: Rosetta's Landing Unit Philae

7.4 First Photos to be Taken on a Cometary Nucleus

7.5 The First Science Sequence on a Cometary Nucleus

7.6 The Long-Term Science Sequence Approaching the Sun Piggyback on a Comet

References

Chapter 8: Conclusions and Outlook

8.1 What Do We Learn from Rosetta's Cometary Exploration?

8.2 The Influence of Rosetta's Data on Our Life on Earth

8.3 The Next Steps in Comet Exploration and Chirality

References

Index

End User License Agreement

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Guide

Cover

Table of Contents

Preface

Chapter 1: Introduction

List of Illustrations

Figure 1.1

Figure 1.2

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List of Tables

Table 1.1

Table 1.2

Table 1.3

Table 2.1

Table 2.2

Table 3.1

Table 4.1

Table 4.2

Table 4.3

Table 5.1

Table 6.1

Table 7.1

Table 7.2

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Uwe Meierhenrich

Comets and their Origin

The Tool to Decipher a Comet

Author

Uwe Meierhenrich

Université Nice Sophia Antipolis

Institut de Chimie de Nice

France

[email protected]

Cover

Rosetta Orbiter and Lander: The Orbiter swoops low over the Lander soon after touchdown on the nucleus of Comet 67P/Churyumov-Gerasimenko.

Copyright by Erik Viktor, with kind permission by the artist.

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Print ISBN: 978-3-527-41281-5

ePDF ISBN: 978-3-527-41278-5

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For Ingrid and Gerhard

Foreword by Michael F. A'Hearn

As this is being written, the Rosetta spacecraft has awakened from its long hibernation and phoned home. The history stored in memory has been downlinked and is being examined on the ground, and various operational functions are being tested. Next month, there will be sufficient power to begin turning on the scientific instruments, and we will see the start of a revolution in cometary science. That is the context for this book, which explores our knowledge of comets and what we might expect for new knowledge from Rosetta. Assuming that the scientific return is as exciting as we expect, we can hope that some parts of this book will be made obsolete by the mission, while other parts are filled in with many new details and insights.

Why do we care about comets? They are, at least occasionally, the most exciting thing one can ever see in the nighttime sky, and those occasional comets stimulate tremendous public curiosity about comets. They represent a small fraction of the bodies that impact Earth, but they are among the larger ones, such that it behooves us to understand their physical properties in order to be prepared if one should be discovered on an impact trajectory. Most importantly, however, they retain critical information about the origin of the Solar System because they are small, with no internally generated heat and thus no chemical reactions, and they are the least chemically altered bodies in the Solar System that we are likely to explore in the foreseeable future. In other words, they should provide the best record of the chemical conditions, and thus the physical conditions present at the time of the Solar System formation. Convergence between dynamical studies and observations of physical and chemical properties will enable us to relate those conditions to specific locations in the protoplanetary disk, and the interplay between those fields is crucial. This is what drives my own particular interest in comets and that of other scientists who want to understand the formation of the solar system.

One can predict some of the areas in which Rosetta will have a tremendous impact. In physical properties of the nucleus, the CONSERT experiment is expected to provide the first structural information on the deep interior of the nucleus. This will provide crucial data that will constrain the accretion processes that produced the nucleus and may also provide information on later evolution through discovery of near-surface voids. The various composition-measuring instruments on Philae (APXS, COSAC, and MODULUS) coupled with ROSINA's mass spectrometer for gas and COSIMA's analysis of individual grains on the orbiter will provide an unprecedented inventory of the chemical species in the comet. Even more important, observations will be carried out from three astronomical units inbound, through perihelion and part of the way back out, thus making an unprecedented leap in understanding how comets work over their orbital timescale. This in turn is crucial for determining which properties of a given comet are likely primordial and which are likely the result of evolution since formation and scattering to the two reservoirs known today (the scattered disk and the Oort cloud).

Observations of the changes in outgassing, coupled with images of the surface at high resolution (both from the cameras on Philae and from the OSIRIS cameras on the orbiter) to see how the surface changes and how the topography is related to outgassing, will be crucial in understanding the mechanisms that make a comet a comet. This in turn is crucial in learning how best to interpret the wealth of remote sensing data on the material that has left the nuclei of many comets. This generalization from comet P/Churyumov–Gerasimenko to all comets, or at least to most short-period comets, is crucial for placing the comets in their proper context for scenarios of the Solar System formation.

One lesson that needs to be kept in mind from previous missions to comets is that every comet has yielded surprises that upset one or another of our conceptual understandings of comets. Rosetta should be no exception to this pattern. We cannot predict whether the surprises will be in chemical composition, in nuclear structure, in nuclear topography and surface processes, or in coma flow properties. It is sufficient to be ready for surprises in any portion of the investigations with Rosetta. It is these surprises that could make some portions of this book obsolete within a few years, but this book will survive as an important record of our understanding just before the presumed changes that occur with every investigative leap into the unknown.

This book provides an overview of comets as we now understand them, of the instruments and operations of the Rosetta mission, and of the scientific results that are anticipated from Rosetta. The book is, appropriately, very light on the dynamics and dynamical history of comets, because this is an area that rests on the ensemble of comets and to which Rosetta will likely not make substantial contributions. We do need to remember, however, that it is the interplay between dynamical histories of comets as an ensemble and physical/chemical properties to best extent that we can measure them that will bring us true understanding. The book emphasizes the chemical side of the Rosetta investigations and its relationship to life, which is the author's particular interest and, for that matter, close to my own. This ties directly to the larger questions of origins – How did life arise on Earth and what did comets bring to Earth that enabled life to arise? What was brought to comets from the interstellar medium and what was created (in the sense of molecules being formed, condensed, and accreted) in the formation zone of comets in the protoplanetary disk?

In the first half of the book, the author crosses disciplines to integrate them into a coherent picture, using laboratory studies of organic chemistry and life, searches for life outside Earth, previous missions to comets, formation scenarios for comets, and studies of meteorites. In the second half of the book, the author surveys the planned operations of Rosetta and the anticipated early science, ending with the likely impact of Rosetta on future scientific investigations into life on Earth and future space exploration. We can all hope that the return from Rosetta will meet our expectations.

Michael F. A'Hearn

Maryland

U.S.A.

Foreword by Gerhard H. Schwehm

2014 and 2015 will be the years of Rosetta, ESA's comet rendezvous mission. The spacecraft will approach comet 67P/Churyumov–Gerasimenko in June 2014 and start to characterize it from close quarters. For the first time, we will monitor a comet nucleus from close distance and follow the onset of activity. After a detailed characterization and mapping of the comet, a landing site will be selected, and by the mid-November, the Philae lander will be deployed onto the nucleus. Subsequently, the Rosetta orbiter will stay with the comet on its path through the inner Solar System, its perihelion passage, and through its outbound leg. The 11 instruments onboard will provide a wealth of data from imaging to spectroscopy covering a wide wavelength range from the ultraviolet to submillimeters. Mass spectrometers will analyze the composition of the gases and the dust released from the nucleus, we expect for the first time to get information on the interior structure of the nucleus, and a suite of plasma instruments and a dust detector will monitor the near-nucleus environment. ESA with the Rosetta science team promised to bring a laboratory to the comet; the first step has been achieved, now we are waiting for the laboratory to work.

Rosetta's rendezvous with the comet will take place about 30 years after the successful flybys at comet 1P/Halley in March 1986. These flybys have been performed by the European Space Agency's Giotto spacecraft, the Soviet Union's Vega 1 and Vega 2 spacecraft, and farther away the Japanese Suisei and Sakigake.

Giotto showed for the first time a close-up of a comet nucleus to confirm F. Whipple's theory from the early 1959s that a comet is a frozen snowball, the source of the wonderful display we sometimes see when a comet comes close to the sun displaying its dust and plasma tails. Since then our knowledge about comets has made huge progress; in 2001 NASA's Deep Space 1 flew by comet 19P/Borrelly, and in January 2004 NASA's Stardust passed comet 81P/Wild 2 and returned samples from the coma to Earth in 2006. In its extended mission phase, Stardust-NeXT revisited comet 9P/Tempel 1 in 2011, who had been the target of NASA's Deep Impact mission in 2005. In its extended phase, the Deep Impact spacecraft passed close to comet 103P/Hartley 2 in 2010.

Also ground-based observation techniques improved with extended time at large telescopes have been devoted to comet observations. Two bright comets in the mid-1990s of the last century, Hyakutake and Hale-Bopp, provided unique opportunities for ground-based spectroscopic observations. And we should not forget the large infrared space observatories, ESA's ISO and Herschel and NASA's Spitzer all provided excellent new results casting new light on cometary science. And we should not forget ESA's veteran solar space observatory SOHO that detected hundreds of comets grazing the Sun. We have learned a lot, but still:

Where do we come from, how did the Solar System evolve? These are two primary questions that interest scientists and the general public alike. And comets might be the key to answer these questions: to look back into the infancy of our Solar System, and to the material out of which and the conditions in which the planets formed.

Comets, the dirty snowballs as we describe them, are the leftovers from the formation of the Solar System about 4.6 billion years ago. They have been stored at low temperatures far away from the Sun in the Kuiper belt or the Oort cloud at low temperatures as in a deep freeze, and due to their small size their material has not been differentiated by their own gravity, they contain the most primitive, unaltered material from the beginning of our Solar System accessible to us.

Determining the chemical composition, the structure, and physical properties of the material in a comet nucleus will give us information about the temperature and pressure environment in the presolar nebulae and help us to unravel the evolution history of our planets, including their diversity.

The science of comets covers a wide fascinating field, and Prof. Meierhenrich addresses in this book the basic theories of how comets work, the physics and chemistry of comets, and the materials in comets. As a renowned expert of complex organic chemistry, he especially provides a detailed account of this fascinating aspect of comet science: comets are believed to have provided a significant amount of raw materials to the early Earth. Water that might be contributing to the oceans and the complex organic molecules with organic material embedded in the dust grains might have contained the precursor material needed for the emergence of life.

Comet science is not only about comets, it is about the origin of our Solar System, the evolution of the planets, and possibly the evolution of life. Only if we understand the basics, we can study these fascinating objects as a system, putting all the single findings in the bigger context. Prof. Meierhenrich provides us with the background of the knowledge we have about comets today and the tools to understand the wealth of new data Rosetta promises to provide, and it hopefully will trigger the curiosity of many young researchers to start their own investigations of one of the many challenges that cometary physics and chemistry provide. For the established scientist, it will provide a fresh look at certain areas and perhaps will provide a new perspective to tackle problems in a wider context.

Studying comets has never been boring, and I am sure that Rosetta will bring us the next big step in our understanding of the evolution of our Solar System and why we are here on Earth.

Gerhard H. Schwehm

Former Project Scientist of Rosetta and since launch

Mission Manager

Noordwijk

The Netherlands

Preface

Scientific and public interest in comets is significant. Comets are the most numerous and most pristine objects in the Solar System. They store scientific information about the origin of both the Solar System and the biosphere on Earth. Comets have been messengers and carriers of water and other important molecules, and today, their message is close to being deciphered. Therefore, we continue to be fascinated by these enigmatic objects.

In many aspects, the study of comets is the study of origins. Comets contain information – mineralogical, chemical, and structural information, as well as isotopic clues – about the origin and formation of the Solar System. Furthermore, comets include crucial information about the origin and evolution of planets, including their water inventory, and the origin of the formation of molecules, thereby providing important clues about the origins of life itself, including chirality-related phenomena. Therefore, the title of this book is Comets and their Origin.

The first part of this book will introduce and characterize comets. Based on the information obtained by the Vega, Sakigake, Suisei, and Giotto space probes, which investigated comet 1P/Halley, and also the cometary missions Deep Space 1, Stardust, Deep Impact, Stardust-NExT, and EPOXI, which visited Kuiper belt comets, the book will present our current understanding of the physical and chemical composition of different comets. It will introduce the formation of interplanetary dust particles, Brownlee particles, and the Greenberg model for the formation of cometesimals and comets. It will explain artificial comets that can be generated in the laboratory, and it will describe organic molecules, including the amino acids identified in comets. The book will outline a coherent model for the origin of life on Earth that is motivated by the molecular inventory of comets. Because the origin of life is assumed to require asymmetric precursor molecules, the asymmetric synthesis of chiral organic molecules in artificial comets will be presented. Data will be compared with the enantiomeric excesses identified in different meteorites.

This book aims to link comet data obtained from astronomical studies with experimental astrophysics and widen these fields to include chemistry, biology, and geology.

After Part I, which presents our current understanding of comets and their origin, the book will describe the most recent and ongoing cometary mission, Rosetta, which aims to reach comet 67P/Churyumov–Gerasimenko in August 2014 and to land on the surface of its nucleus in November 2014. Part II of this book begins with Rosetta's launch from Kourou, French Guiana, which was delayed because of a dramatic explosion of an Ariane 5 launcher prior to the originally planned Rosetta launch date in 2002. The book will then describe Rosetta's journey to the target comet Churyumov–Gerasimenko, including its flyby maneuvers around Mars, Earth, and asteroids. On Rosetta's way to the target comet, the space probe observed comet 9P/Tempel during the Deep Impact mission in 2005 and the asteroids Šteins in 2008 and Lutetia in 2010. The data obtained will be presented. The book will describe and characterize Rosetta's target comet, 67P/Churyumov–Gerasimenko. After reaching comet Churyumov–Gerasimenko, the Rosetta spacecraft will enter into an artificial orbit and begin its initial comet observation phase. The soft landing of the landing unit Philae on the cometary nucleus will be described in detail. Initial photos will be taken on the surface of the cometary nucleus, and the first science sequence, using selected scientific instruments, will start. After the presentation of detailed information on the landing and first science sequence, the long-term science sequence will be described. The book will outline the scientific objectives by describing general scientific questions and how the Rosetta instruments will help to answer them. Some of these questions concern the origins of terrestrial water and the molecular beginnings of life on Earth. The book will end with a chapter on what we, scientists, concretely expect from the cometary mission Rosetta and how Rosetta's data will influence our life on Earth. The first pictures and analyses of the comet will arrive on Earth some weeks after the publication of this book. The general aim of the book is to prepare the mind of the scientific community for the landing of Rosetta on the comet and the science that will be performed.

The Rosetta space probe aims to land on a cometary nucleus in November 2014. The mission and landing will attract significant interest from astronomers and astrophysicists, as well as physicists and space engineers. Because the transdisciplinary instrumentation onboard Rosetta's orbiter and the landing unit Philae – which is to be used to investigate cometary organic molecules, isotopic composition, chirality phenomena, and symmetry properties – scientists from disciplines such as geology, chemistry, biochemistry, and biology became involved in this mission. Geologists will use isotope fingerprinting to decipher crucial steps in the formation of the planetary system, including the origin and formation of terrestrial minerals and water. Since 1990, many chemists have contributed to the identification of scientific objectives and the development of the Rosetta mission. The mission will thus address important and new fields of chemical evolution, chirality, and stereochemistry. Astrochemistry is a new domain that will be involved. The life sciences that focus on the origin and evolution of enzymatic and genetic molecules will be addressed. Here, the new and dynamic domains of astrobiology/exobiology and bioastronomy come into play.

Science books, in general, and interdisciplinary science books, in particular, should not be composed of endless lists of facts without appropriate discussions and critical comments. The proposed book will avoid an uncommented listing of the physical parameters of different comets in the form of tables. The aim of the proposed book is rather to present a general science framework for the Rosetta cometary mission. The book should enter into the scientific debates and discussions generated by Rosetta's different instruments and be appreciated by the reader.

Authoring this book, I was fortunate to work with and learn from Professor Wolfram H.-P. Thiemann at the University of Bremen. He introduced me to the intriguing fields of chirality and cometary research. The international collaboration in my research field on the origin of life's molecular asymmetry was initiated by Dir. Dr Helmut Rosenbauer at the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, via the ambitious conception and preparation of the COSAC experiment onboard the Rosetta lander. My thanks go to Dr Rosenbauer for this scientific support and his colleagues Dr Fred Goesmann and Dr Reinhard Roll for their fascinating basic work on COSAC and for plenty of conferences in the midst of fruitful discussions.

It was also a great pleasure to carry out scientific research within the international COSAC team including Dr Hermann Boehnhardt, Dr Jan Hendrik Bredehöft, Dr Jean-Francis Brun, Dr Michel Cabane, Dr Antonio Casares, Dr David Coscia, Professor Pascale Ehrenfreund, Professor Guy Israel, Laurent Janin, Dr Oliver Kuechemann, Professor Takekiyo Matsuo (†), Dr Guillermo M. Muñoz Caro, Professor François Raulin, Dr Harald Steininger, Dr Robert Sternberg, Dr Cyril Szopa, Dr Stephan Ulamec, and Professor H. Wollnik, who provided their full cooperation and scientific support. I also appreciate related discussions with Dr Franz R. Krueger, Professor Kensei Kobayashi, and Dr Jun-ichi Takahashi.

Intensive experimental collaborations were performed with Professor J. Mayo Greenberg (†) at the Raymond and Beverly Sackler Laboratory for Astrophysics at the Leiden Observatory and his group composed of Dr Guillermo M. Muñoz Caro, Dr Willem A. Schutte, and Almudena Arcones Segovia. I acknowledge the pleasant cooperation with Professor Greenberg's Ph.D. student Guillermo M. Muñoz Caro, now at the Astrobiology Center in Madrid, and his carefully performed experiments on the simulation of interstellar ices with isotopically labeled reactants.

I thank for the generous support of Dir. Dr André Brack from the Centre de Biophysique Moléculaire in Orléans. Advanced experiments with circularly polarized light were performed at the Synchrotron Centers LURE and SOLEIL in Paris at beamlines SA-61, SU-5, and DESIRS. I would like to acknowledge the staff of these research centers and especially the substantial and advanced studies of Dr Laurent Nahon on both the generation and detection of circularly polarized synchrotron radiation. Thanks also go to Dr Louis d'Hendecourt and Dr Pierre de Marcellus from the Institut d'Astrophysique Spatiale in Paris-Orsay and to Dr Martin Schwell from the Université Paris VII Denis Diderot. I also appreciate to work with Dr Søren V. Hoffmann and Nykola C. Jones at beamlines UV-1 and CD-1 at Århus University, Denmark, in the Center of Storage Ring Facilities. I wish to thank Dr Max P. Bernstein for his contributions and Dr Jason P. Dworkin (both at NASA Ames Research Center, Moffet Field, California) for discussions on enantioselective chromatographic techniques for samples of interstellar ice analogs.

Moreover, I acknowledge lively discussions on the multifaceted cometary phenomena with all members of my research team at the Institut de Chimie de Nice (ICN) of the University Nice Sophia Antipolis, namely, Dr Nicolas Baldovini, Emilie Belhassen, Dr Jean-Jacques Filippi, Chaitanya Giri, Dr Cornelia Meinert, Iuliia Myrgorodska, and Oriane Tascone.

The author thanks the Deutsche Forschungsgemeinschaft (DFG), Bonn, and the Agence Nationale de la Recherche (ANR), Paris.

And I would like to thank the well-disposed reader not only for following the ideas and concepts exposed in this book, but also for feedback, frank criticism, and suggestions.

Nice, Cap d'Ail

Uwe Meierhenrich

France

March 2014

List of Abbreviations and Symbols

Symbols and abbreviations were used according to the list below. In some cases, such as P or R, one symbol has more than one meaning. The proper meaning becomes clear from the context in which the symbol is used.

1P

Comet 1P/Halley

2P

Comet 2P/Encke

3D

Comet 3D/Biela

6P

Comet 6P/d'Arrest

8P

Comet 8P/Tuttle

9P

Comet 9P/Tempel 1

14P

Comet 14P/Wolf

15P

Comet 15P/Finlay

17P

Comet 17P/Holmes

19P

Comet 19P/Borrelly

26P

Comet 26P/Grigg–Skjellerup

31P

Comet 31P/Schwassmann–Wachmann 2

46P

Comet 46P/Wirtanen

67P/C-G

Comet 67P/Churyumov–Gerasimenko

73P

Comet 73P/Schwassmann–Wachmann 3

81P

Comet 81P/Wild 2

85P

Comet 85P/Boethin

88P

Comet 88P/Howell

95P

Comet 95P/Chiron

103P

Comet 103P/Hartley 2

122P

Comet 122P/de Vico

133P

Comet 133P/Elst–Pizarro

A

Absorption

aeg

N

-(2-Aminoethyl)glycine

AFM

Atomic force microscope

amu

Atomic mass unit

ALICE

Rosetta's UV imaging spectrograph

APXS

α-Particle X-ray spectrometer onboard Philae

AU

Astronomical unit

B

Magnetic field vector

β

Decay process of unstable atomic nuclei

c

Concentration

C/1969 T1

Comet Tago–Sato–Kosaka

C/1969 Y1

Comet Bennett

C/1975 V1

Comet West

C/1983 H1

Comet IRAS-Araki-Alcock

C/1986 P1

Comet Wilson

C/1989 X1

Comet Austin

C/1990 K1

Comet Levy

C/1995 O1

Comet Hale–Bopp

C/1996 B2

Comet Hyakutake

C/1999 S4

Comet LINEAR

C/2000 WM1

Comet LINEAR

C/2001 A2

Comet LINEAR

C/2001 Q4

Comet NEAT

C/2002 C1

Comet Ikeya–Zhang

C/2003 K4

Comet LINEAR

C/2004 B1

Comet LINEAR

C/2004 Q2

Comet Machholz

C/2012 S1

Comet ISON, comet Nevski–Novichonok

CAI

Calcium- and aluminum-rich inclusion

CAP

Comet acquisition point

CASSE

Comet acoustic surface sounding experiment, part of SESAME

CCD

Charge-coupled device

CD

Circular dichroism

CIDA

Cometary and interstellar dust analyzer onboard Stardust and Stardust-NExT

CIP

Cahn–Ingold–Prelog

CIVA

Comet infrared and visible analyzer onboard Philae

CKR

Cometary kilometric radiation

CONSERT

Comet nucleus sounding experiment by radio-wave transmission

CONTOUR

Comet nucleus tour

COSAC

Cometary sampling and composition experiment onboard Rosetta

COSIMA

Cometary secondary ion mass analyzer onboard Rosetta

cp

Circularly polarized

D/1993 F2

Comet Shoemaker-Levy 9

d

Absolute enantiomer configuration related to d-glyceraldehyde

d

Optical path length

da

2,4-Diaminobutyric acid

DAP

2,3-Diaminopropanoic acid

DE

Disconnection event

DFMI

Dust flux monitor instrument onboard Stardust

DFMS

Double-focusing magnetic mass spectrometer

DIDSY

Dust impact detection system onboard Giotto

DIM

SESAME's dust impact monitor

DLR

Deutsches Zentrum für Luft- und Raumfahrt

DMA

Dimethylacetal

DMF

Dimethylformamide

DPU

Data processing unit

DS1

Deep Space 1

DUCMA

Dust counter and mass analyzer onboard Vega

Δ

Geocentric distance

e

Orbital eccentricity

E

Electrical field vector

ECAS

Eight-color asteroid survey

ee

Enantiomeric excess

EPOXI

Extrasolar Planet Observation and Deep Impact Extended Investigation

ESOC

European Space Operations Centre

EUV

Extreme ultraviolet

ϵ

Molar extinction coefficient

F

c

Flux of reflected sunlight

F

grav

Gravitational force

F

rad

Force of the solar radiation pressure

FSS

First science sequence

FTIR

Fourier transform infrared

FUV

Far-ultraviolet

F

Solar flux at

r

= 1 AU

g

Anisotropy factor

GC×GC

Multidimensional gas chromatography

GC-MS

Gas chromatography coupled with mass spectrometry

GEMS

Glass with embedded metal and sulfides

GIADA

Grain impact analyzer and dust accumulator onboard Rosetta

GRE

Giotto Radio-Science Experiment

HCS

Heliospheric current sheet

HGA

High-gain parabolic dish antenna

HMC

Halley multicolor camera onboard Giotto

HPLC

High-performance liquid chromatography

HST

Hubble Space Telescope

i

Inclination of the orbital plane relative to the plane of the ecliptic

ICA

Ion composition analyzer, part of Rosetta's RPC

ICE

International Cometary Explorer Mission

ICM

International Comet Mission

IDP

Interplanetary dust particle

IES

Ion and electron sensor, part of Rosetta's RPC

IMS

Ion mass spectrometer onboard Giotto

IPS

Ion propulsion system

IRTF

NASA's Infrared Telescope Facility

ISAS

Japanese Institute of Space and Aeronautics

ISO

Infrared Space Observatory

ISON

International Scientific Optical Network

IUE

International Ultraviolet Explorer

JAXA

Japan Aerospace Exploration Agency

JCMT

James Clerk Maxwell Telescope

JPA

Johnstone Plasma Analyzer onboard Giotto

KAO

Kuiper Airborne Observatory

l

Absolute enantiomer configuration related to l-glyceraldehyde

LAP

Langmuir Probe, part of Rosetta's RPC

LGA

Low-gain antenna

LINEAR

Lincoln Near-Earth Asteroid Research

LTS

Long-term science

λ

Mean free path length

M

Prefix of a chiral helical structure

MAG

Fluxgate Magnetometer, part of Rosetta's RPC

MCP

Micro-channel plate

MDM

Multi detector mode of HMC

MGA

Medium-gain antenna

MICAS

Miniature integrated camera and spectrometer onboard DS1

MIDAS

Microimaging dust analysis system onboard Rosetta

MIP

Mutual Impedance Probe, part of Rosetta's RPC

MIRO

Microwave instrument for the Rosetta orbiter

MOMA

Mars organic molecule analyzer

MSL

NASA's Mars Science Laboratory

MUPUS

Multipurpose sensor package onboard Philae

NAC

OSIRIS narrow-angle camera

NEAT

Near-Earth Asteroid Tracking

NMR

Nuclear magnetic resonance

NMS

Neutral mass spectrometer onboard Giotto

NPCC

Lutetia's North Polar Crater Cluster

ν

e

Electron neutrino

Antineutrino

ξ

Extent of reaction

OMC

Orion molecular cloud

OSIRIS

Optical, spectroscopic, and infrared remote imaging system onboard Rosetta

p

Geometric albedo

P

Periodicity

P

Prefix of a chiral helical structure

PAH

Polycyclic aromatic hydrocarbon

PEPE

Plasma experiment for planetary exploration onboard DS1

PHA

Potentially hazardous asteroid

PIA

Dust mass spectrometer onboard Giotto

PIU

Plasma Interface Unit, part of Rosetta's RPC

PNA

Peptide nucleic acid

POM

Polyoxymethylene

PP

SESAME's permittivity probe

PTOLEMY

Gas analyzer onboard Philae

PUMA

Dust impact mass analyzer onboard Vega

q

Perihelion distance in AU

QCM

Quartz crystal micro-balance

r

Heliocentric distance

R

Distance to the cometary nucleus

R

Absolute enantiomer configuration according to CIP notation

RMOC

Rosetta Mission Operations Centre

R

MS

Mass spectrometer resolution

ROLIS

Rosetta lander imaging system

ROMAP

Rosetta magnetometer and plasma monitor

ROSAT

Röntgen satellite

ROSINA

Rosetta orbiter spectrometer for ion and neutral analysis

RPC

Rosetta Plasma Consortium

RSI

Rosetta's Radio Science Investigation

S

Cross section of the cometary nucleus

S

Absolute enantiomer configuration according to CIP notation

S

0–3

Stokes parameters

SAM

Sample analysis at Mars

SD2

Philae's sampler drill and distribution system

SDL

Separation, landing, and descent

SDM

Single detector mode of HMC

SEP

Solar electric propulsion

SESAME

Surface electric sounding and acoustic monitoring experiment

SIMS

Secondary ion mass spectrometry

SOHO

Solar and Heliospheric Observatory

SP-1

Dust particle counter onboard Vega 1

SP-2

Dust particle counter onboard Vega 2

SREM

Standard Radiation Environment Monitor onboard Rosetta

SST

Spitzer Space Telescope

STXM

Scanning transmission X-ray microscopy

SWCX

Solar wind charge exchange

T

Tisserand parameter

T

Time of perihelion passage

TCD

Thermo conductivity detector

TIC

Total ion chromatogram

TKS

Three-channel spectrometer onboard Vega

TNA

Threofuranosyl nucleic acid

UKIRT

United Kingdom Infrared Telescope

VIRTIS

Rosetta's infrared imaging spectrometer

VLT

Very Large Telescope

VSMOW

Vienna Standard Mean Ocean Water

φ

(

α

)

Phase function normalized to the phase angle

α

WAC

OSIRIS wide-angle camera

ω

Argument of perihelion

Ω

Longitude of the ascending node as measured east from the vernal equinox

XANES

X-ray absorption near-edge spectroscopy

z

Charge

Part IComets and their Origin

1Introduction

1.1 Preliminary Remarks

The word comet originates from the Latin comta or comts and from the Greek κoμήτης or komts. It is derived from κóμη kóm, which means “the hair of the head” or “long hair.” The astronomical symbol for comets is , which shows a circle with three hair-like lines.

Comets are fascinating and important objects that merit profound and serious scientific investigation for various, often multidisciplinary reasons [1]: comets are assumed to reveal information about