Planetary Geology

Vita-Finzi Claudio

Description

Recent planetary missions by NASA, the European Space Agency and other national bodies have reaffirmed that geological processes familiar from our studies of the Earth operate on many solid planets and satellites. Common threads link the internal structure, thermal evolution and surface character of both rocky and icy worlds, and volcanoes, impact craters, ice caps, dunes, rift valleys, rivers and oceans emerge as features of extra-terrestrial worlds as diverse as Mercury and Titan. The new data also reveal that many supposedly inert planetary bodies currently experience eruptions, landslides and dust storms. Moreover our understanding of the Solar System has greatly benefited from the analysis of meteorites from Mars as well as rock samples collected on the Moon. Combining extensive use of imagery, the results of laboratory experiments and theoretical modelling, this comprehensively updated second edition of Planetary Geology provides the student reader and the enthusiastic amateur with up-to-date coverage of these recent advances and confirms that, to quote from the first edition, planetary geology now embraces conventional geology and vice versa.Note for Teachers using this book with students. The authors have prepared some ancillary materials for class use. To gain access to these materials please use the contact form and tell us where and when you will be using the book and with how many students.

Sujets

• Sciences et techniques

Informations

• Publié par: Dunedin Academic Press
• Date de parution: 20 juin 2013
• Nombre de lectures: 0
• EAN13: 9781903544877
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

Note to readers:
Owing to the complexity of the layout of the book as printed, the illustrations do not appear in the text of this ebook where they appear in the hard copy. To access any illustration, click on the appropriate reference in the text. Doing so will take you to the illustration in question with a hypertext link provided to take you back to the point you were at in the text. [The default setting is to return you the Chapter in which the figure is mainly referenced. Some figure appear in more than one chapter. Depending on your epub reader you can use the back to page feature of the reader to return to the point in the text that you were reading before you linked to the illustration. For example, there is the 'Back to page #' option in the lower left panel of the iPad or the 'Go Back' Button of the Kindle Fire device.]

To the memory of John E. Guest 1938–2012 Pioneer planetary geologist
Contents
   Preface to the first edition
   Preface to the second edition
     1      Planetary origins
     2      Orbits and cycles
     3      Core, mantle, crust
     4      Magnetic fields and signatures
     5      Topography and gravity
     6      Tectonics
     7      Volcanism
     8      Impacts and impactors
     9      Atmospheres
    10    Oceans and ice caps
    11    Erosion, deposition and stratigraphy
    12    Planetary biology
   References
   Glossary
   Index
How great would be the desire in every admirer of nature to behold, if such were possible, the scenery of another planet .
Charles Darwin, Voyage of the Beagle .
Preface to the first edition
'Thirty years ago', a member of the Astrogeology Team of the US Geological Survey recently commented, 'planetary science was the purview of a small number of astronomers concerned with determining first-order information on the elements and compounds that made up our nearest neighbors in the heavens. Today...these...have emerged as whole worlds in their own right. Not simply pocked with craters as our own Moon [they have] volcanoes, complex ridged and grooved terrain, icecaps, and possibly, oceans under icy crusts' (Calvin 1998).
Planetary geology is an introductory textbook designed to present current ideas about the origin and evolution of these new worlds. A geological approach to planetary exploration was being championed within NASA in the 1960s and 1970s, and although the first Apollo mission to include a professional geologist was the last (Apollo 17, 1972), all the astronauts contributed by observation, sampling and instrumentation to the great advances in lunar geology achieved by that programme. Most of the unmanned missions to the planets, their satellites, asteroids and comets have had a strong geological component even when it has been obscured by other, perhaps more flamboyant aims: the search for evidence of life, for example, or the first landing on an asteroid. The results (and techniques) have enriched conventional geoscience; they have also broadened its potential syllabus to include much more atmospheric physics, geodesy and biochemistry than is habitual, and topics which once seemed esoteric, such as the study of meteorites and the mechanics of impacts, move centre stage.
More generally, Earth can no longer be presented as the normality with which to compare Mars, Venus or the icy moons: the geological evolution of our planet has much in common with that of its rocky neighbours; it too is prey to impact by comets and bathed in cosmic rays and the solar wind; and, even if life should turn out to be uniquely Earthly, we need to consider how and why.
This book originated in a course I gave at University College London for a dozen years to students in a wide range of departments, which was entitled Earth and Planetary Geology , a distinction that should sound as incongruous as 'human and animal evolution'. Yet even now many geology and geomorphology textbooks refer to planets other than Earth in a concluding chapter or appendix, if at all, and even then mainly to highlight their bizarre or improbably familiar appearance as revealed by telescopes and probes, just as many astronomy books say little about Earth beyond a mournful comment on its fragile beauty as seen from afar. The book promotes the notion that planetary geology should form an integral part of Earth Science – and vice versa. Students using a conventional, Earthbound, geoscience textbook would not be disconcerted to come across California next to the central Atlantic Ocean in a chapter on faulting, or modern Iceland and the Sahara in Silurian times in a discussion of basalt. I hope that they will find it equally natural to move from Antarctica to Europa when dealing with frozen oceans or between the Great Red Spot of Jupiter and Earth's anticyclonic systems in a review of circulation patterns. When the list of examples is a long one they are arranged according to distance from the Sun (Mercury, Venus, Earth, our Moon, etc.), but the aim is to illustrate rather than exhaust.
Some authorities see geology as primarily the study of the solid parts of the planets and are thus not greatly concerned with the gaseous giant planets, the solar wind, comets and much else that nowadays demands inclusion in a geoscience text. Astrogeology, which has been defined as the discipline covering the overlap between geology and astronomy, reflects the lively exchange of ideas and data between astronomers and geologists as Earth is increasingly found to reflect the influence of solar and interplanetary forces in its biology as much as in its physical composition, but to the newcomer the word conveys the study of stars and galaxies rather than planets and their satellites, and although nearly a hundred planets have been identified outside our Solar System since 1995, and we know something about the mass and atmospheric composition of a handful, their geology still remains too conjectural to justify detailed discussion here. Planetary geology conveys just about the right mix of familiar and novel material.
Unfamiliar terms and abbreviations are defined when first encountered in the text or, if appropriate, in the glossary, but I hope there will still be scope for quality examination howlers such as the claim in a UCL exam script written in 1999 that a dense cloud cover accounts for the libido of Venus. In general the power notation (x 10 4 etc.) is used for small and large numbers except for Myr (in preference to Ma) for 10 6 years, Gyr (rather than Ga or aeon) for 10 9 yr and μm for 10 –9 m. Similarly, SI units are favoured except where (as with bar in atmospheric contexts) to do so would obscure rather than clarify the sense. Numbers listed in the tables have generally been rounded up or down (and deprived of their error values) as they are intended mainly for comparison. Worldwide Web addresses were correct at the time of going to press.
I am much indebted to Dominic Fortes for comments, data and some very fine diagrams, Roger Jones for editorial guidance and for redrafting many of the figures, John Guest and several anonymous reviewers for their advice, Simon Tapper for help with the graphics, and Matt Balme, Simon Day, Adrian Jones and David Price for illustrations. My greatest debt is to NASA for allowing us all to benefit freely from its missions.
CVF
Preface to the second edition
Ten years have passed since the first edition. The decade has witnessed some astounding discoveries thanks to many missions, technological progress and theoretical advances. These in turn have called for changes in nomenclature. For instance, in 2006 the International Astronomical Union defined a planet as a celestial body which (a) is in orbit around the Sun (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (i.e., is approximately spherical) shape, and (c) has cleared the neighbourhood around its orbit. Pluto failed the test and was demoted to the rank of dwarf planet. At present there are four other dwarf planets: Ceres, Haumea, Makemake and Eris.
The number of known planets outside our solar system exceeded 880 in May 2013 and we have a shrewd idea of the surface temperature and atmospheric composition of a few of them, but the information required to study their geology is still lacking. On the other hand the number of satellites of the eight planets and five dwarf planets has grown (as we write) to 179, some asteroids have now been imaged in sufficient detail to qualify for inclusion here, and the infall and discovery of meteorites continues to enrich our collections.
Despite numerous TV programmes illustrating the wonders of the solar system, and a number of popular books explaining its workings, the field is studied by a small minority of geoscience and astronomy students. In order to keep within a specified length we have sacrificed some detail for the sake of brevity, but we hope there is enough here to confirm that geology has gained much from exploring the varied bodies in our solar system and that, contrary to some opinions, planets do not simply get in the way of real astronomy.
CVF & ADF
Chapter 1
Planetary origins
An understanding of the composition, internal dynamics and evolution of the planets and their satellites demands a historical perspective that extends back to the beginnings of the Solar System and the context afforded by comparison with solar systems in all stages of development circling other stars. The difficulties are magnified by the extraordinary range of scales, both in time and space, over which phenomena occur. From the dance of individual ions in the solar wind to the more sedate movement – atom by atom – of the Earth's mantle as it convects, we are challenged to discern singular events from cyclic behaviour or from long-term trends. On Earth, the readily-apparent cyclicity of the seasons, the tides and even minute changes in the length of the day, must be understood agains