Scientific Rationale for Mobility in Planetary Environments Committee on Planetary and Lunar Exploration Space Studies Board Commission on Physical Sciences, Mathematics, and Applications National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1999 NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. 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Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. William A. Wulf are chairman and vice chairman, respectively, of the National Research Council. Support for this project was provided by Contract NASW 96013 between the National Academy of Sciences and the National Aeronautics and Space Administration. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the organizations or agencies that provided support for this project. International Standard Book Number 0-309-06437-6 Copyright 1999 by the National Academy of Sciences. All rights reserved. COVER: An artist's impression of various forms of mobility that might be employed by future Mars exploration missions. Lander, rover, and balloon images courtesy of the Jet Propulsion Laboratory. Aircraft image courtesy of Malin Space Science Systems. Composite by Penny E. Margolskee. Copies of this report are available free of charge from: Space Studies Board National Research Council 2101 Constitution Avenue, NW Washington, DC 20418 Printed in the United States of America COMMITTEE ON PLANETARY AND LUNAR EXPLORATION RONALD GREELEY, Arizona State University, Chair FRANCES BAGENAL,* University of Colorado JEFFREY R. BARNES, Oregon State University RICHARD P. BINZEL, Massachusetts Institute of Technology WENDY CALVIN, U.S. Geological Survey RUSSELL DOOLITTLE, University of California, San Diego HEIDI HAMMEL, Massachusetts Institute of Technology LARRY HASKIN, Washington University BRUCE JAKOSKY, University of Colorado KENNETH JEZEK, Ohio State University GEORGE McGILL, University of Massachusetts HARRY McSWEEN, JR., University of Tennessee MICHAEL MENDILLO, Boston University TED ROUSH,* San Francisco State University JOHN RUMMEL,* Marine Biological Laboratory GERALD SCHUBERT, University of California, Los Angeles EVERETT SHOCK, Washington University EUGENE SHOEMAKER,* Lowell Observatory Staff DAVID H. SMITH, Study Director JACQUELINE ALLEN, Senior Program Assistant SHARON SEAWARD, Program Assistant ERIN HATCH, Research Associate STEPHANIE ROY, Research Assistant BRIDGET ZIEGELAAR, Research Assistant *Formermember. iii SPACE STUDIES BOARD CLAUDE R. CANIZARES, Massachusetts Institute of Technology, Chair MARK R. ABBOTT, Oregon State University FRANCES BAGENAL, University of Colorado, Boulder DANIEL N. BAKER, University of Colorado, Boulder LAWRENCE BOGORAD,* Harvard University DONALD E. BROWNLEE,* University of Washington ROBERT E. CLELAND, University of Washington GERALD ELVERUM, JR., TRW Space and Technology Group ANTHONY W. ENGLAND,* University of Michigan MARILYN L. FOGEL, Carnegie Institution of Washington RONALD GREELEY, Arizona State University BILL GREEN, former member, U.S. House of Representatives CHRISTIAN JOHANNSEN, Purdue University ANDREW H. KNOLL, Harvard University JONATHAN I. LUNINE, University of Arizona ROBERTA BALSTAD MILLER, CIESIN-Columbia University BERRIEN MOORE III,* University of New Hampshire GARY J. OLSEN, University of Illinois, Urbana MARY JANE OSBORN, University of Connecticut Health Center SIMON OSTRACH,* Case Western Reserve University MORTON B. PANISH,* AT&T Bell Laboratories (retired) CARLI_ M. PIETERS,* Brown University THOMAS A. PRINCE, California Institute of Technology PEDRO L. RUSTAN, JR., Ellipso Inc. JOHN A. SIMPSON,* Enrico Fermi Institute GEORGE L. SISCOE, Boston University EUGENE B. SKOLNIKOFF, Massachusetts Institute of Technology EDWARD M. STOLPER, California Institute of Technology NORMAN E. THAGARD, Florida State University ALAN M. TITLE, Lockheed Martin Advanced Technology Center RAYMOND VISKANTA, Purdue University PETER VOORHEES, Northwestern University ROBERT E. WILLIAMS,* Space Telescope Science Institute JOHN A. WOOD, Harvard-Smithsonian Center for Astrophysics MARC S. ALLEN, Director (until December 12, 1997) JOSEPH ALEXANDER, Director (as of February 17, 1998) *Formermember. iv COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND APPLICATIONS PETER M. BANKS, ERIM International Inc., Co-chair W. CARL LINEBERGER, University of Colorado, Co-chair WILLIAM BROWDER, Princeton University LAWRENCE D. BROWN, University of Pennsylvania MARSHALL H. COHEN, California Institute of Technology RONALD G. DOUGLAS, Texas A&M University JOHN E. ESTES, University of California, Santa Barbara JERRY P. GOLLUB, Haverford College MARTHA P. HAYNES, Cornell University JOHN L. HENNESSY, Stanford University CAROL M. JANTZEN, Westinghouse Savannah River Company PAUL KAMINSKI, Technovation Inc. KENNETH H. KELLER, University of Minnesota MARGARET G. KIVELSON, University of California, Los Angeles DANIEL KLEPPNER, Massachusetts Institute of Technology JOHN R. KREICK, Sanders, a Lockheed Martin Company MARSHA I. LESTER, University of Pennsylvania M. ELISABETH PATI_-CORNELL, Stanford University NICHOLAS P. SAMIOS, Brookhaven National Laboratory CHANG-LIN TIEN, University of California, Berkeley NORMAN METZGER, Executive Director Preface Planetary surfaces and atmospheres are complex, with physical and chemical properties that vary over a large range of spatial scales. To understand such variegated features we need multipoint measurements and/or mobile platforms. 1. For planetary atmospheres, scientific payloads carried by a fleet of balloons could enable synoptic mea- surements of chemical compositions and physical characteristics as functions of depth, latitude, and longitude. Measurements could be made for significantly longer times than those typical of entry probes. 2. For planets with solid surfaces, mobility is essential. The case is exemplified for Mars, where spacecraft mobility would enable major advances in understanding climate change and geologic history and in searching for direct evidence of past life. This would require landers that can reach identified targets and there analyze selected materials. 3. Given the extensive round-trip communication times involved in interplanetary exploration, a significant degree of autonomy may also be required. Power needs and communication rates will inevitably be major considerations, as will cost. Given the importance of mobility-related issues to the achievement of priority objectives in the planetary sciences, the Space Studies Board charged the Committee on Planetary and Lunar Exploration (COMPLEX) to review the science that can be uniquely addressed by mobility in exploring the atmospheres and surfaces of planetary bodies. In particular, COMPLEX was asked to address the following questions: • What are the practical methods for achieving mobility? • For surface missions, what are the associated needs for sample acquisition?