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



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--> 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

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--> 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. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. 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

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--> 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 *   Former member.

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--> 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) CARLÉ 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) *   Former member.

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--> 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 PATÉ-CORNELL, Stanford University NICHOLAS P. SAMIOS, Brookhaven National Laboratory CHANG-LIN TIEN, University of California, Berkeley NORMAN METZGER, Executive Director

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--> 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. For planetary atmospheres, scientific payloads carried by a fleet of balloons could enable synoptic measurements 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. 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. 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? What are past examples of planetary mobility systems and how effective have they been in addressing important issues in the planetary sciences? What is the state of technology for planetary mobility in the United States and elsewhere, and what are the key requirements for technology development? What terrestrial field demonstrations are required prior to spaceflight missions?

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--> Although this project was formally initiated in May 1997, presentations in support of it began in September 1995. They were conducted in a variety of contexts, including COMPLEX's standing oversight of NASA's planetary exploration programs and during the definition and development of the charge for this study. This report also draws on material presented to COMPLEX in the preparation of a number of additional reports. These include "Scientific Assessment of NASA's Solar System Exploration Roadmap" (letter report to Jurgen Rahe, August 23, 1996), "Scientific Assessment of NASA's Mars Sample-Return Mission Options" (letter report to Jurgen Rahe, December 3, 1996), and the Space Studies Board's assessment of the draft Office of Space Science strategic plan (letter report to Wesley Huntress, Jr., August 27, 1997). Many of the presentations dealt primarily with technological issues, but the potential for science was explicitly discussed as well. Background material was also gathered during COMPLEX's February 1997 meeting at the Jet Propulsion Laboratory. In addition, three members of COMPLEX actively participated in one or more field tests of the Russian Marsokhod rover and the facilities of NASA Ames Research Center's Intelligent Mechanisms Group, and two were involved with operational tests of the Sojourner rover carried by the Mars Pathfinder mission. In conjunction with COMPLEX's June 1997 meeting in Flagstaff, Arizona, committee members participated in field trips to the Upheaval Dome impact feature in southeastern Utah and Meteor Crater in northeastern Arizona to gain direct experience of the mobility needed for the characterization of complex geologic features. Although many COMPLEX members past and present worked on this report, the bulk of the task of assembling their many individual contributions was performed by George McGill with the assistance of Jeffrey Barnes, Richard Binzel, Ronald Greeley, Heidi Hammel, Bruce Jakosky, Hap McSween, Ted Roush, Gerald Schubert, and Everett Shock. The work of the writing team was made easier thanks to the contributions made by Michael Carr (U.S. Geological Survey), Frank Carsey (Jet Propulsion Laboratory), James Cutts (Jet Propulsion Laboratory), Michael Drake (University of Arizona), Stephen Gorevan (Honeybee Robotics), Andrew Ingersoll (California Institute of Technology), Arthur Lane (Jet Propulsion Laboratory), John Langford (Aurora Flight Sciences), Daniel McCleese (Jet Propulsion Laboratory), Christopher McKay (Ames Research Center), Kenneth Nealson (Jet Propulsion Laboratory), Kerry Nock (Jet Propulsion Laboratory), Paul Schenker (Jet Propulsion Laboratory), Alan Treiman (Lunar and Planetary Institute), Koichiro Tsuruda (Institute of Space and Astronautical Science), Charles Weisbin (Jet Propulsion Laboratory), and Brian Wilcox (Jet Propulsion Laboratory). This report has been reviewed by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the National Research Council's (NRC's) Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the authors and the NRC in making the published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The contents of the review comments and draft manuscripts remain confidential to protect the integrity of the deliberative process. COMPLEX thanks reviewers Benton Clark (Lockheed Martin Corp.), Larry Crumpler (New Mexico Museum of Natural History and Science), Larry Esposito (University of Colorado), Richard Greenberg (University of Arizona), Roald Sagdeev (University of Maryland), Steven W. Squyres (Cornell University), and Joseph Veverka (Cornell University) for many constructive comments and suggestions. Responsibility for the final content of this report rests solely with the authoring committee and the NRC.

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--> Foreword The cautious wanderings of the intrepid Sojourner rover across the martian surface in 1997 captured the attention of much of the world—the Jet Propulsion Laboratory's World Wide Web site broke records for the number of visitors hungry for the latest snapshots of the Red Planet. More to the point, Sojourner's ability to snuggle up to one rock after the other and assay its composition multiplied manifold the scientific return of the Mars Pathfinder mission. This report is a cross-cutting assessment of the role of mobility in meeting the scientific objectives of planetary research as previously set out by the Space Studies Board's Committee on Planetary and Lunar Exploration. For a wider range of scientific goals, the ability to sample multiple locations on a planet's surface or in its atmospheres is found to be of great importance. This leads to some technological and programmatic considerations for developing the most effective means of achieving mobility in planetary environments. NASA's Space Science Enterprise Strategic Plan1 presages a steady drumbeat of launches to Mars, Europa, and other planetary bodies over the next decade. As with Sojourner, careful attention to the most effective strategies for mobility will significantly enhance the capabilities of these future missions to explore the solar system, providing large scientific returns as they also stimulate public interest. CLAUDE R. CANIZARES, CHAIR SPACE STUDIES BOARD 1   National Aeronautics and Space Administration, The Space Science Enterprise Strategic Plan: Origin, Evolution, and Destiny of the Cosmos and Life, National Aeronautics and Space Administration, Washington, D.C., 1997.

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--> Contents     Executive Summary   1 1   Introduction   5     Historical Perspective,   5     What Is Mobility?,   6     Organization,   7     Scientific Goals for Solar System Exploration,   8     Specific Objectives and Case Studies,   8     References,   10 2   The Role of Mobility in Solar System Exploration   12     Circulation in the Lower Atmosphere of Venus,   12     Tectonic Processes on Venus,   14     Extinct or Extant Life on Mars,   17     Physical and Chemical Heterogeneity Within Small Bodies,   18     Zonal Winds in the Jovian Atmosphere,   21     Europa's Internal Structure,   23     References,   25 3   Technological Capabilities   28     Achieving Mobility,   28     Sample Acquisition,   44     Terrestrial Field Demonstrations,   48     References,   50 4   Conclusions and Recommendations   53     References,   56

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