CHARLES J. BYRNE THE MOON’S LARGEST CRATERS AND BASINS Images and Topographic Maps from LRO, GRAIL, and Kaguya The Moon’s Largest Craters and Basins Charles J. Byrne The Moon’s Largest Craters and Basins Images and Topographic Maps from LRO, GRAIL, and Kaguya Charles J. Byrne Middletown , NJ , USA ISBN 978-3-319-22031-4 ISBN 978-3-319-22032-1 (eBook) DOI 10.1007/978-3-319-22032-1 Library of Congress Control Number: 2015949139 Springer Cham Heidelberg New York Dordrecht London © Springer International Publishing Switzerland 2016 This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or part of the material is concerned, specifi cally the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfi lms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specifi c statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained herein or for any errors or omissions that may have been made. Cover: Thin crust is red and thick crust is blue in this false color map of part of the South Pole-Aitken Basin on the Moon’s far side. The map combines GRAIL gravity data with LRO elevation data. Printed on acid-free paper Springer International Publishing AG Switzerland is part of Springer Science+Business Media (www.springer.com) This book is dedicated in gratitude to Mary, my beloved and diligent wife, and others who patiently and helpfully tolerated my preoccupation during the preparation of this book. Pref ace L unar research fi rst interested me when Dr. Dennis James recruited me from Bell Laboratories to join the Apollo project as a system engineer in 1961. We worked at Bellcomm, Inc., a contractor with NASA headquarters. My specifi c assignment was to gather the information to select and certify land- ing sites for the fi rst manned landings, sample collection, and safe return. As you might imagine, such a broad charter led us to work with some of the leading scientists and engineers of the time who were interested in such a challenging task. T his was the background for my current interest in lunar science and exploration. A continuing interest has been the question of the striking differences between the near side of the Moon and the far side, revealed by the Lunar Orbiter cameras we used to fi nd Apollo landing sites. This dichotomy could have been caused by a great collision between a very large asteroid (a planetesimal) and the Moon after it had formed and its crust hardened. The encompassing basin it formed, the Near Side Megabasin, is the fi rst impact feature of this Catalog and is the subject of Appendix A, along with alternate hypoth- eses of how the Moon got its unusual shape, with a low near side and a large bulge on the far side. Recently, there has been renewed interest in astronauts returning to the Moon, with projects started, stopped, and renewed. A natural result of this interest is the launch of several spacecraft projects for exploration of the Moon by remote sensing from orbit. This book incorporates information collected by the Kaguya, Lunar Reconnaissance Orbiter (LRO), and the Gravity Recovery and Interior Laboratory (GRAIL) missions. This has brought a new generation of researchers forward, bringing with them new analysis techniques to explore the history of the Moon. An important part of the Moon’s history has been to establish the sequence of the lunar basins, the largest impact features on the Moon, at least 300 km in diameter. Techniques developed after the Apollo missions were applied, resulting in a comprehensive review of the sequence of basins by the US Geological Survey in 1987 that became the traditional view for decades. With the new remote sensing data and analytical techniques, this work has been updated, again concentrating on the basins. This book reexamines both the traditional view and the new work on basins and extends it to the large craters, those with diameters larger than 200 km but smaller than basins. Chapters 6 through 9 (arranged by stratigraphic period) are the backbone of this book, collectively called the Catalog. The images, graphs, and maps on 72 large features on the Moon are assembled in two pages apiece, all placed in sequence. The list includes 27 features between 200 km and 300 km in diameter. The advan- tage of having the large craters included with the basins is that they seem to have a relatively steady rate in the sequence, after an initial period of giant events that obscure the early craters. The ages of basins, examined by analysis of samples since Apollo days, appear to be concentrated in short time frames, called the Early Heavy Bombardment and the Late Heavy Bombardment. The relation of large craters to basins in the sequence confi rms this. vii viii Preface T he methods of sequencing the features assembled in this Catalog are described in detail in Chap. 2 . Once the sequence was assigned, the data collected was available for analysis, reported in Chaps. 3 , 4 , and 5 . These reports both support the value of the sequenced Catalog and also provide new information on the Moon’s history: • Examining the diameters relative to the Sequence Number for each impact feature (Chap. 3 ) leads to distinguishing the specifi c basins that are associated with the Early Heavy Bombardment, the Late Heavy Bombardment, and the background events of the large craters. This distinguishes two populations of events in the Late Heavy Bombardment, with implications on the history of the Solar System. • A study of the depths of the impact features relative to their diameters (Chap. 4 ) provides insight into which features retain their initial depths and which have relaxed since then. This reveals evidence of the thermal history of the Moon in time and place. • The very new gravity anomaly results of the GRAIL mission are related to the diameters and places of the impact features (Chap. 5 ) . Insights from new 3D simulations are related to the gravity data with implications concerning thermal history. Some important topics too broad or detailed for the pages of the Catalog are covered in appendices: • T he reasons for the Near Side Megabasin being assigned Sequence Number 1 as the cause of the extraordinary shape of the Moon are given in Appendix A , along with a discussion of alternate hypotheses. • N ew understanding of the Procellarum Region in the eastern and central near side of the Moon is presented in Appendix B. Analysis of GRAIL data is combined with traditional observation and understanding to propose an explanation of the causes of the outpouring of lava in the region. • T he rim and ejecta blanket of the South Pole-Aitken Basin (SPA) are revealed in maps in Appendix C. The cavity of the SPA has been well studied and related to mineral and magnetic variations, but the rim and ejecta were never clear because they were imposed on the preexisting far side bulge. By subtracting a model of the Near Side Megabasin from the current topography, the rim and ejecta blanket of the SPA are revealed. • T he phenomenon of isostatic compensation is examined in detail and related to sequence and place in Appendix D. The results are analyzed further in Chap. 4 . T he topics of this book should be considered an interim report on the work of many researchers and many data collecting missions. In particular, the GRAIL mission resulted in the identifi cation of pre- viously unknown impact features on the basis of their gravity signals. Some of these features are included in this Catalog. Others are discussed in Chap. 2 and as notes but are not included in this Catalog because there was not enough information about them to assign a specifi c Sequence Number. In the future, further analysis of these features may justify placing them in sequence. T he task of assigning Sequence Numbers and the task of deciding which features are worthy of sequencing are ones of judgment. Not everyone has the same judgment and I, for one, will be inter- ested in new sequences and the resulting analyses. I hope that the contents of this Catalog will be useful to future efforts. Middletown, NJ, USA Charles J. Byrne Contents 1 Introduction to the Sequenced Catalog of the Moon’s Largest Craters and Basins ................................................................................................. 1 2 Generating the Sequence of Features ................................................................................. 7 3 Feature Diameter as a Function of Sequence Number ...................................................... 15 4 Initial Depth and Later Isostatic Compensation ............................................................... 21 5 Bouguer Gravity Anomaly Patterns of Impact Features .................................................. 29 6 The Pre-Nectarian Period .................................................................................................... 35 7 The Nectarian Period ........................................................................................................... 129 8 The Early Imbrian Period ................................................................................................... 175 9 The Late Imbrian Period ..................................................................................................... 185 Acknowledgements ..................................................................................................................... 193 References and Notes .................................................................................................................. 195 Glossary ....................................................................................................................................... 209 Gazetteer (Tables G.1 and G.2) .................................................................................................. 215 Appendix A: The Moon’s Topographic Dichotomy and the Near Side Megabasin .............. 221 Appendix B: The Procellarum Region ...................................................................................... 227 Appendix C: The South Pole-Aitken Basin .............................................................................. 233 Appendix D: Method of Computing Relative Compensation ................................................. 239 Index ............................................................................................................................................. 243 ix