2101 Constitution Avenue, N.W.Washington, DC20418

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.

This study was supported by Contracts No. NASW-96013 and No. NASW-99037 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 views of the agency that provided support for the project.

International Standard Book Number: 0-309-08426-1

Cover: “First Light,” by Pat Rawlings and commissioned by NASA, depicts the first human travelers to Mars exploring the enormous Noctis Labyrinthus canyon system. Just after sunrise, early morning fog masks the canyon floor 4 miles below. These scientists-explorers conduct geological and meteorological research in order to help us better understand the characteristics of our sister planet and possibly our own Earth. Reproduced courtesy of the artist and NASA.

Available in limited supply from Aeronautics and Space Engineering Board, HA 292, 2101 Constitution Avenue, N.W., Washington, DC 20418, (202) 334-2855

Additional copies available for sale from

National Academy Press,
2101 Constitution Avenue, N.W., Box 285, Washington, DC20055, 1-800-624-6242or (202) 334-3313(in the Washington metropolitan area),

Copyright 2002 by the National Academy of Sciences. All rights reserved.

Printed in the United States of America

The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement