MARS BECKONS The Mysteries, the Challenges, The Expectations of Our Next Great Adventure in Space By John Noble Wilford Knopf. 244 pp. $24.95

DEATH RAYS. Flying saucers. John Carter battling alien creatures for the love of scantily clad Dejah Thoris. The panic of 1938, when the invasion force landed at Grovers Mill, N.J. Little green men. An arid, dying world of romance and adventure.

The Babylonians called it Nergal; 3,000 years later Edgar Rice Burroughs renamed it Barsoom. For many of us Mars will always be, above all, the evil empire of Saturday afternoon at the movies when we hunched in our seats, gripping Tom Corbett ray guns, watching "The War of the Worlds," "Invaders from Mars," "This Island Earth." On those hot summer days, we would walk home after the show and, glancing occasionally up at the sky, speculate about the age-old question: "What would you do if the Martians landed in your backyard?"

In 1877 the Italian astronomer Schiaperelli peered through his telescope and spotted strange lines criss-crossing the planet's surface. He called them canali, which can mean channels or grooves, but was translated into English as canals. According to Carl Sagan, everything started there: "Somebody says canals on Mars. Well, what does that mean? Well, canal -- everybody knows what a canal is. How do you get a canal? Somebody builds it. Well, then there are builders of canals on Mars." Martians.

In two of the best chapters of Mars Beckons, New York Times science reporter John Noble Wilford outlines the flights of fancy that followed the discovery of the Martian "canals." The key figure was Perceval Lowell, a wealthy American amateur of Asian culture who out of the blue decided to build a telescope and spend the rest of his life studying Mars. Lowell confirmed the canal sightings -- now generally believed to have been optical illusions -- and then started to speculate about the character of the planet and its probable inhabitants. In one of his popular books, he wrote, "We have before us the spectacle of a world relatively well on in years, a world much older than the earth." This notion -- that Mars was an old planet -- led swiftly to the corollary that it might support an ancient civilization, might be the home of a once vigorous people now grown decadent. Lowell's romantic wish, richly fulfilled by early science-fiction writers, helped transform the planet into a haunted, dying world.

For instance, in The Sword of Rhiannon (1953), set on a time-worn Red Planet, Leigh Brackett describes her hero as he "walked beside the still black waters in their ancient channel, cut in the dead sea-bottom . . . Lean lithe men and women passed him in the shadowy streets, silent as cats except for the chime and whisper of the tiny bells the women wear, a sound as delicate as rain, distillate of all the sweet wickedness of the world." Who could resist swashbuckling adventures against such a backdrop?

Many of the scientists at the Jet Propulsion Laboratory and at NASA stayed awake as kids reading Burroughs, Brackett and Ray Bradbury (the wistful Martian Chronicles). They yearned for a Mars commensurate with their dreams. As late as 1960, Wilford tells us, a respected Russian astronomer could speculate that Mars's two moons, Phobos and Deimos, were actually artificially constructed satellites.

But thanks to Viking 1, which landed on the alien planet's surface on July 20, 1976, we now know that Mars is a rocky, arid, freezing cold world. The southern hemisphere is pock-marked with craters and looks as desolate as the Moon. The northern hemisphere, by contrast, shows evidence of past geological upheavals, including a huge volcano called Olympus Mons, twice as high as Everest with a crater 50 miles wide; a canyon system named Valles Marineris equal in length to the continental United States, with deep chasms over 100 miles wide; and numerous ancient channels caused by flooding waters. The two poles, which shrink and grow with the seasons, are covered with frozen carbon dioxide -- dry ice. The temperatures at the equator range from a high of 0 degrees F to a low of -150. There are no signs of life.

But dreams die hard. Even after the lander's pictures revealed nothing but rocks, red soil (due to the heavy iron content) and salmon-pink skies, Carl Sagan admitted to "this recurring fantasy that we'll wake up some morning and see on the photographs footprints all around Viking that were made during the night, but we'll never get to see the creature that made them because it is nocturnal." A leader of the Viking project had earlier rejected Sagan's request for a lighting system. Carl, he said, "also talked about putting out bait."

The best part of Mars Beckons is its first half, which relates the history of mankind's fascination with the Red Planet and the actual discoveries of Viking 1 and other Mars surveys. Along the way, Wilford talks about Johann Elert Bode, the 18th-century astronomer best known for Bode's Law ("each planet is roughly twice as far from the Sun as the previous one"); the Roche limit, which is the nearest a satellite can go into a planet's gravitational field without being pulled in or apart; the code word that sent Viking 1 on its way, the appropriately Martian-like "KVUGNG"; and the fact that "an astronaut on Phobos could . . . throw objects with sufficient velocity for them to escape the moon's gravity." Such facts are entrancing in themselves, just the sort of good reading one would expect from the author of The Mapmakers and The Riddle of the Dinosaurs.

Nonetheless Wilford, perhaps inevitably, loses some momentum in his later chapters, those dealing with the future exploration of Mars. Here the fascinating science -- robotic explorers, the problems of long periods in weightless flight, terraforming -- gets entangled with dull questions of space policy, possible cooperation with the Soviets, financial priorities and even some corny platitudes about man's destiny among the stars (e.g. People need to believe that "it is never too late to try to change their tormented history while in the bold act of moving the human drama out to a new and distant stage").

The Soviets -- despite many past failures in their space missions -- have long planned to send men to Mars, and it would seem to our mutual advantage to go together. Last year, President Bush called for just such a collaboration. But right now a Soviet-American expedition for early in the 21st century, perhaps in the company of Europeans, Japanese and other spacefaring nations, depends on a good many unknowns, including a currently unstable Soviet internal policy. Not that the U.S. is particularly clear on its own goals. Some moderates, in light of our own troubled space program, suggest that we first learn to survive on the Moon before mounting an expedition to Mars. Others feel that we should concentrate on robotic exploration, which tends to produce useful scientific results, rather than expensive, flag-waving human missions. Some others are simply getting ready to go, among them members of the Mars Underground and the project known as Biosphere II.

Inevitably, barring global self-destruction, human beings will travel to the Red Planet. One day, sooner or later but almost certainly sometime in the next century, we will become Martians.

Michael Dirda is a writer and editor for Book World.