ACKNOWLEDGMENTS<br >No single scientist， or even three， can have all the expert<br >knowledge， much less the balanced perspectives， needed to do<br >justice to the present state of knowledge concerning the<br >surfaces of the Earthlike planets. To the extent we have<br >succeeded in producing a useful book， the helpful criticism<br >and suggestions of many of our colleagues have been essential.<br >We wish to acknowledge in particular reviewers of specific<br >portions of the manuscript: Professor Arden Albee， Division of<br >Geological and Planetary Sciences， and Jet Propulsion<br >Laboratory， Caltech; Dr. Michael Carr and Dr. Newell Trask，<br >United States Geological Survey; Dr. Clark R. Chapman and Dr.<br >William K. Hartmann， Planetary Science Institute; Dr. Fraser P.<br >Fanale， Jet Propulsion Laboratory， Caltech; Dr. Donald E. Ganlt，<br >Murphys Center of Planetology; Professor John E. Guest，<br >University of London， England; Professor William M. Kaula，<br >Department of Earth and Space Sciences， and Institute of<br >Geophysics and Planetary Physics， University of California，<br >Los Angeles; Professor Robert B. Leighton， Division of Physics，<br >Mathematics， and Astronomy， Caltech; Dr. Peter H. Schultz and<br >the late Dr. Thomas R. McGetchin， Lunar and Planetary<br >Institute; Professor Robert P. Sharp， Division of Geological and<br >Planetary Sciences， Caltech; Professor Robert G. Strom， Lunar<br >and Planetary Laboratory， University of Arizona; and Dr.<br >George W. Wetherill， Department of Terrestrial Management，<br >Carnegie Institution of Washington.<br > In addition， Dr. Carl Sagan of Cornell l.)niversity， Dr. Thomas<br >Mutch of Brown University， and Mr. Paul D. Spudis of Arizona<br >State University reviewed the entire book-length manuscript<br >