Moon Hunters: NASA's Remarkable Expeditions to the Ends of the Solar System

Moon Hunters: NASA's Remarkable Expeditions to the Ends of the Solar System

by Jeffrey Kluger

In Moon Hunters, bestselling author Jeffrey Kluger tells the thrilling story of some of the most remarkable heavenly bodies known — the solar system's sixty-five moons — and the extraordinary people who have explored them all. Chronicling lunar exploration from the first attempts by NASA's Jet Propulsion Laboratory to explore our own moon to the


In Moon Hunters, bestselling author Jeffrey Kluger tells the thrilling story of some of the most remarkable heavenly bodies known — the solar system's sixty-five moons — and the extraordinary people who have explored them all. Chronicling lunar exploration from the first attempts by NASA's Jet Propulsion Laboratory to explore our own moon to the triumphant conquest of the outer planets, Moon Hunters is an adventure story full of drama, danger, and suspense. While taking the reader on a spellbinding journey to the eerie landscapes of the moons themselves, Moon Hunters offers a riveting account of the scientists and spacecraft responsible for unlocking the secrets of the cosmos — and perhaps of life itself.

Editorial Reviews

Carolyn T. Hughes
Jeffrey Kluger, a senior writer at Time and the author, with Jim Lovell, of Apollo 13, does a fine job chronicling both the difficulties and successes the laboratory has faced during its 40-year history with NASA...
NY Times Book Review
Publishers Weekly - Publisher's Weekly
Unmanned spaceships have investigated all the planets in our solar system except Pluto. More significant to NASA's search for extraterrestrial life, these spaceships have also beamed back vivid closeups of 63 moons. For it is on moons like Jupiter's ice-covered satellite Europa that scientists believe we may discover primitive forms of life. Kluger, a writer for Time magazine and coauthor of the bestselling Lost Moon, does a terrific job of tracing the history of NASA's Jet Propulsion Laboratory, whose scientists have directed the unmanned exploration of space from the first failed attempts to land on earth's moon (Selene) to the Pioneer and Voyager missions that captured the public's imagination with their color photos of giant gas planets and bizarre moons. Kluger wisely doesn't dwell on the bureaucracy and infighting always present in an institution as large as JPL, but he does portray enough of it for readers to appreciate how pressured the staff were to produce a spacecraft that could reach the moon and send back pictures. Kluger's explanations of the technical hurdles faced in guiding a tiny spaceship close to as many planets as possible without either hitting them or being set off course by their gravity can be followed easily by anyone with a general science background. His descriptions of our small galactic neighborhood convey scientists' excitement about what we may find when a probe lands on one of these strange worlds. An enticing narrative of scientific exploration, this book is strongly recommended to anyone interested in the search for life in space. 8-page color insert. Agent, Joy Harris. (July) Copyright 1999 Cahners Business Information.
Library Journal
A senior writer at Time who covers science and particularly the space program takes us on a journey to the many moons in the solar system beyond our own.
Kirkus Reviews
As is detailed here, there is more than one moon in the solar system, and many of them are far more interesting than our own. Kluger, a veteran space journalist for Time and co-author with Jim Lovell of Lost Moon: The Perilous Voyage of Apollo 13 (1994), focuses on NASA'S Jet Propulsion Laboratory (JPL), in Pasadena, Calif., where much of the serious business of exploring our solar system is conducted. Before the Apollos sent men to the moon, JPL sent probes to scout out safe landing sites—there was some speculation that the moon was covered with a deep layer of fine dust in which the landers would sink without a trace. After several embarrassing failures, a Ranger probe successfully crash-landed on the lunar surface, proving it to be solid rock. By the time the Apollos landed, JPL was already planning trips deeper into space. Its greatest triumph undoubtedly came with the Voyager probes launched in 1977 to take advantage of an unusual planetary alignment to explore Jupiter, Saturn, and (with Voyager 2) Uranus and Neptune, and their moons. Kluger details both the technical and the bureaucratic problems JPL faced in getting the Voyager missions working, then gives the reader the story of their remarkable results: the discovery of dozens of new moons orbiting the four planets, as well as the return of close-up photographs of the previously known ones, many reproduced in full color here. The discoveries included active volcanos on Jupiter's moon Io, Europa's surface of cracked water ice (suggesting oceans below), and the fragmented face of Uranus's moon Miranda. These and other results constitute nothing short of a revolution in planetary astronomy. The reader also gets a goodlook at the inner workings of NASA and JPL, with due attention to the unsung technicians who do much of the real work. Kluger's style is a bit on the cheeky side, but on the whole he does his subject justice. A solid survey of a major advance in our knowledge of the solar system.

Product Details

Simon & Schuster
Publication date:
Edition description:
Product dimensions:
6.12(w) x 9.22(h) x 0.81(d)

Read an Excerpt

from the Prologue

Pasadena, Calif., July 1979-March 1997

Linda Morabito was alone in her lab when she discovered that the moon was exploding. Actually, there was some question as to whether it was a moon that was exploding at all. A lot of people -- Morabito included -- had begun to regard the body more as a fully certified planet, and a lot of other people were coming around to that way of thinking, too. But the official position at NASA's Jet Propulsion Laboratory in Pasadena where Morabito worked was that the maybe-planet was indeed a moon, so that's what Morabito generally called it. In any event, it was exploding.

Morabito did not know exactly what she was expected to do if she found out the moon was exploding today. Earlier in the day would have been different, but earlier in the day she wasn't the only one here. Indeed, earlier in the day it seemed that everybody was here: the head of the lab, the head of the department, the head of the whole space agency flown in special from Washington. That was the way it always was on picture days, and there was no reason today would have been any different.

Picture days, it seemed, almost always happened on a Thursday or a Friday, and for a place like JPL, that made sense. When you're showing off the first images of some new world taken by a billion-dollar spacecraft a half billion miles from home, you want to schedule things carefully. Call your press conference too early in the week and the newsmagazines that don't come out until next Monday start to see your stuff as stale. Call it too late and they can't get their stories written up by their Friday-night deadlines. No, if you want your pictures to get anywhere beyond the four walls of the JPL imaging room where the hot pixels sent back from the remote robot probe were first assembled into images, you had to call the reporters in, give them what they needed, and have them on their way no later than lunchtime Friday.

Morabito, of course, was not invited to participate in the press conference earlier today -- and she didn't expect to be. Nobody from spacecraft navigation ever was. The way the media saw things, the navigation section's job was merely to get a spaceship (in this case, Voyager 1) from some terrestrial Point A (in this case, Cape Canaveral) to some cosmic Point B (in this case, Jupiter) in as little time as possible. Never mind that there were 400 million miles between Jupiter and Florida. Never mind that, at its absolute fastest, the little tin ship that was making the trip would never be able to gun its speed much beyond 35,000 miles per hour, a glacial creep that meant it would need years to get where it was going. Never mind that there were a thousand wrong turns the ship could make in the course of its journey, and if it made just one of them it would spin off into the void, never to contact Earth again. No, the reporters didn't care about any of that. What they cared about were the pictures the ship would be beaming home, and it was the planetologists and geologists from the glamorous imaging team -- not the drones from the navigation team -- who would present them to the reporters.

This picture day the crowd of reporters gathering to receive those images promised to be a big one, but it was not images of Jupiter itself they were coming to see. The planet, after all, was something of a known quantity. Little more than a mammoth, spherical storm of hydrogen and helium, Jupiter had long since been regarded not so much as a planet at all, but as a sort of failed star. It had the size to be a star and the age to be a star, but it never achieved the critical ignition mass to light its internal fires and actually become a star. If the solar system had a blown fuse, Jupiter was it.

What circled Jupiter, however, was another matter entirely. Buzzing electron-like around the giant world were no fewer than thirteen moons. It was 369 years earlier that the four biggest of those satellites -- Io, Europa, Ganymede, and Callisto -- were discovered. In later decades, better telescopes added Amalthea and Thebe, Metis, Adrastea, Leda, Lysithea, Elara, Ananke, and Carme. However many other moons there might be was impossible to say, but two years earlier, Voyager 1 and its sister ship, Voyager 2, had been launched toward the outer planets to help find out. What intrigued the scientists and the media following the progress of the ships was not merely the exact number of the moons, but the possibility that something might be going on on them.

The moon astronomers knew best -- Earth's moon -- was, by even the most generous assessments, a carcass of a world: uniformly gray, uniformly dry, uniformly dead. From as far away as Earth, however, astronomers could see that the Jovian moons were a different matter entirely. There were big moons and small moons, patterned moons and plain moons, brightly colored moons and pasty-pale moons. More important, if remote studies with telescopes and spectroscopes were any indications, there were moons that could have atmospheres, water, and even, perhaps, a spark of internal heat. Put them together, and you had moons that could, in theory, harbor life.

It was the life part that interested the reporters most. And it was the internal heat part that was likely to make the difference. No amount of air, water, and organic molecules was going to be able to do all the clever recombining it had to do to create living organisms if you didn't have something to keep them all warm. Out in the interplanetary provinces where Jupiter lies, however -- where the sun looks little bigger than a lit match held across the room and offers little more heat -- warmth was not such an easy thing to come by. Any energy sufficient to warm a planet-like body this remote would thus have to come from the interior of the planet-like body itself. A place like Earth is a furnace of a world, with a molten core and viscous mantle generating enough heat to keep volcanoes percolating, geysers spouting, and the very continents themselves floating around on all the geological goo like oyster crackers on soup. If a Jovian moon had even a little of this magma-heated metabolism, it just might be able to cook up something living.

That was the theory anyway, and it was one that the press was eager to learn more about as the first of the Voyager ships completed its Jupiter flyby and the late-week press conference got under way. For this initial meeting of the media, the focus would be on what Voyager 1 had been able to learn about the Jovian moon Io -- and even the uninitiated appreciated that this was a good choice. Astronomers already knew that Io appeared to have at least a few wisps of atmosphere and a few riverbed-like gulleys, indicating flowing liquid had once been present on its surface. What's more, the surface of the satellite showed a surprising variety of color -- with orange and black highlands broken up by ruddy, rusty plains. A moon with this much apparent chemistry going on was a moon that was capable of anything.

It was with much anticipation, then, that the JPL scientists awaited the first batch of Io photos beamed back by the little Voyager ship. When the images finally arrived, however, they were, by most measures, a disappointment. Io might have been a dramatic place -- tricked out in all the colors Earthbound astronomers had promised it would be -- but it also appeared to be a dead place. Nowhere on the surface of the moon was there visible volcanic activity or any other sign of the underground heating the scientists had hoped to find. Io's trace atmosphere and complex soil might yet harbor enough raw materials to give rise to living organisms, but with the moon's internal fires obviously having flickered out long ago, any native life would have flickered out, too.

Putting the best scientific face on this forbidding world would not be an easy thing to do on picture day, and when the media gathered today it was clear they were disappointed. The scientists stressed -- and genuinely believed -- that with or without heat, Io was still a chemically fascinating place, that its wealth of organic elements could still teach them a lot about how life evolved on Earth and how it might yet evolve elsewhere. The reporters, however, wanted not chemicals, but critters, and at the same time the scientists were congratulating themselves on making their first successful pass over a world that could keep planetary researchers busy for generations, they found themselves tacitly apologizing to the assembled media for not delivering the organic goods. In four months Voyager 2 would be making its own Jovian flyby, paying special attention to Io's sister moon Europa. If the last moon had been a disappointment, perhaps this next one -- with its brightly reflective surface and its odd, icy rind -- would have more to offer.

When today's picture day ended, the chemists and geologists went home for the weekend, and, as they always did at points like this in a mission, temporarily turned control of the spacecraft over to Linda Morabito and the rest of the navigation team. Now that the ship had completed its first major rendezvous, it would be the navigators' responsibility to take its bearings, check its headings, and make sure it was pointed true toward whatever destination the planetary scientists had chosen for it next. The tools the navigators would use for that job would be the same Io images the planetary scientists had just shown off to the press -- or almost the same Io images.

When a spacecraft tearing along at 7.5 miles per second is taking pictures of a moon that's illuminated by nothing more than a smudge of solar light more than 400 million miles away, exposure time is everything. Leave the shutter of your camera open for too short a period, and the picture you'll get will be nothing but an inky smear. Leave it open for too long, and the exquisitely sensitive light-gathering hardware will gather too much, temporarily blinding itself with the flood of incoming illumination and producing merely a white, washed-out sphere where a picture of a richly textured moon should be. At least half of the Io images Voyager 1 had beamed down were either overexposed or underexposed this way, and while the blackened, underexposed ones did no one any good, the overexposed ones turned out to be surprisingly valuable.

In addition to gathering in the reflected light of the nearby moon, a spacecraft that left its camera's lens cap off too long would pick up lots of tiny pinpoints of starlight. For a navigation engineer like Morabito, this was a very good thing, since there was no better way to confirm that an unmanned ship was adhering to its planned trajectory than to check its position against the stars. Each time an overexposed picture came down from the ship, it was therefore passed on to the navigation section, where celestial map readers like Morabito would determine exactly where in the heavens the spacecraft was, compare this with where it should be, and decide if a course-correcting engine burn was necessary.

On the evening of the Friday press gathering, Morabito sat in her JPL lab, studying her computer screen as it flashed its navigation images with their hopelessly fuzzy Ios and their wonderfully sharp stars. Morabito was the last navigator from the day shift still at her desk, but others, working a voluntary night shift, might be punching in soon. After just a few minutes, however, it became evident that they probably needn't bother. From even a cursory glance at the stars in the Io images, it was clear that Voyager 1 was flying true, with each stellar pinpoint showing up exactly where the navigation charts said it ought to be. Picture after numbingly similar picture told the same encouraging story, when all at once Morabito noticed an image that wasn't so similar. Up near the high horizon of one Io picture, off at the two o'clock position, she spotted a curious bulge in the otherwise smooth disk of the moon. It was like nothing Morabito had ever seen before. The bump was too small to be another Jovian moon peeking out from behind Io, too big to be dust or a pixel glitch in the imaging equipment. It was, undeniably, a part of Io itself.

Morabito dug through a pile of photographic prints for another image taken from the same perspective. The bulge was still there. She found another taken from a few degrees away; again the bulge. Indeed, no matter where VoVoyager 1yager was as it photographed Io's facing hemisphere, the curious mound in the moon's surface remained. It was almost as if there was some odd atmospheric aneurysm swelling over the landscape in a very specific spot. But Io had no atmosphere to speak of -- certainly not one soupy enough to produce such a horizon-transforming cloud.

Morabito worked with the images throughout the evening, calling picture after picture onto her screen and pulling photo after photo out of the stacks that surrounded her. It was only when the night had passed and the sun had risen that Morabito, bleary and still alone in her lab, realized the full magnitude of what she was seeing. This cloud, she now knew, could be only one thing: a plume from an active volcano -- and a huge one. It was rounded like a volcanic plume; it was semi-transparent like a volcanic plume; and it rose over a fixed spot on the surface -- exactly like a volcanic plume. What's more, it rose astoundingly high. Judging by Io's diameter, the cloud of underground hellfire had to extend more than 160 miles into space. If the same exhaust blast occurred on Earth, it would roar into the sky thirty times higher than the peak of Mount Everest. While the plume was big, however, it was also wispy, made more of gas than ash. It was so wispy, in fact, that even Voyager's finely tuned cameras were not sensitive enough to spot it -- at least when they were operating as they should. When they occasionally misfired, however -- such as when they kept their shutters open longer than they ought to -- enough light flowed into the imaging system to make the smoke and gas visible.

Morabito nodded to herself incredulously. Io was alive, explosively alive, home to what appeared to be the most titanically huge volcano in the solar system. And only Linda Morabito -- with her washed-out photos scattered all around her -- knew it.

* * *

It was not until Monday that the rest of the Jet Propulsion Laboratory learned what Linda Morabito had discovered over the weekend. And it was not for another week or so that most of them believed it. But slowly, the evidence mounted. Imaging experts digitally enhanced the Io pictures, and the horizon bulge only became clearer. Planetary scientists analyzed its chemical spectrum and found it consisted mostly of sulfur and fine particles -- just the stuff a volcano would be expected to give off. What's more, other overexposed images from other parts of the moon suggested smoldering volcanoes there as well. At up to nine different spots on the surface, underground heat appeared to be boiling up and blasting into space. Io, it seemed, was a geological pressure cooker, blowing volcanic holes across its own surface like an overinflated beach ball springing spot leaks.

What this meant for life on the moon was impossible to tell. In the vicinity of the volcanoes, surface temperatures appeared to be approaching a shirtsleeves 60 degrees -- more than balmy enough for terrestrial organisms to survive. If the right organic chemicals existed close enough to the volcanoes, it was entirely possible that at least some crude forms of life could have emerged.

The JPL astronomers knew it would be at least a year before they would be able to analyze all of the data Voyager 1 had beamed back and begin to find out for sure. All they could say until then was that the Jovian system was now known to be a hot system -- and hot systems were capable of just about anything. In the meantime, Voyager 2 was still speeding toward its encounter with Europa, and Europa was likely to make things more complicated still.

Earth-based surveys had long since revealed that the Europan landscape was entirely covered by a bright white crust of ice. Moreover, spectral studies had shown that that ice was composed not of methane or caustic sulfur, but of ordinary water. Melt a little of the ice down over even one hot spot on the moon's surface, and you'd have the first ocean known to exist away from Earth. And it was in the oceans that the only confirmed life in the solar system was known to have begun. If Europa had even a fraction of the heat-giving volcanic activity of its sister moon Io, it could be a practical hothouse for extraterrestrial organisms.

As the Voyager 2 flyby of Europa approached, JPL scientists planned frantically. For this encounter, they concluded they would not be so choosy about the pictures they'd examine. Overexposed images, underexposed images, images that were little more than a Europan shimmer would all be studied. Planetary scientists would begin scrutinizing pictures of the moon when the spacecraft was still months away from Europa, looking for even the slightest suggestion of a volcanic plume.

Realistically, however, they knew that if there were volcanoes on Europa, they probably wouldn't reveal themselves so easily. As thick as the moon's ice layer was, even a relatively big eruption would not make it beyond the surface and into the tenuous atmosphere above. Rather, it would stay beneath the frozen crust, heating the lower layers of ice until they turned first into slush and then, perhaps, into flowing water. The only sign the researchers would get that such thermal turmoil was taking place at all would be in the hard ice that still covered the surface. If the Europan crust was pocked with craters, astronomers would know it was an old crust -- one that had been repeatedly pounded by meteor storms without ever being resurfaced afresh. If the astronomers found a patch of smooth surface ice, however, they would know that in that area, heat was rising from deep underground, turning the ice viscous and allowing its craters to be filled in and troweled over. It was beneath those fresh plains that oceans -- and, in theory, life -- might exist.

The day of the Europan encounter, the senior JPL astronomers gathered in the main picture room of the Pasadena complex. Torrence Johnson, the head of the imaging team was there, along with chief planetary scientist Larry Soderblom and chief geologist Brad Smith. Also present was Cornell University astronomer Carl Sagan, who had come to witness the encounter with his usual coterie of graduate students in tow. The images this small group would see today would be projected on half a dozen monitors mounted in heavy steel brackets and bolted to the low-hanging ceiling. The scientists crowded into the room early in the morning, waiting for the moment those monitors would flicker to life. Realistically, they knew it might be a long wait.

From Voyager 2's position deep in Jovian space, the Europa images it beamed to Earth would need a full forty minutes to reach the JPL antennas. From there, the signals would be relayed to a mainframe computer deep in a JPL basement, where they would be rebuilt into a picture. This assembly job would take at least another hour -- maybe two or three -- and only when it was done would the picture be forwarded to the hanging screens in the little room.

At about 8 A.M. Pasadena time, the scientists received word that Voyager had encountered Europa and had switched on its cameras. Exactly forty minutes later they got word that the data from the first image had arrived in Pasadena. An hour elapsed, then two, and finally, deep into the third hour, the ceiling monitors began to sizzle with static. The men looked up and watched as a circular image began to resolve itself on the screens, slipped a little, then resolved again. A dumbfounded silence fell over the room.

"What the hell is that?" someone finally asked.

"What's the matter with the picture?" someone responded. Instinctively, though, the men in the room knew that nothing was the matter with the picture at all.

On the screens in front of them was the unmistakable image of a bright white world covered by a sort of sugar shell of ice with barely a single crater anywhere on it. The shell was shot through with a tracery of fine fractures and spider cracks, but apart from those hairline breaks, it was practically pristine. There wasn't a planet or moon in the solar system that didn't show at least a little meteor scarring somewhere on its surface. And yet Europa -- which could not have been spared the bombardment all of the other worlds had sustained -- had erased virtually all traces of it.

There was only one scientifically sensible explanation. Europa, which the astronomers had hoped might be warm in spots, was warm everywhere. All over the moon there must be enough internal heat radiating up to cause the entire ice crust to soften periodically and then re-form itself. And down below the crust, things would only be more dramatic. There, the warmth just might be so great the water would never freeze at all. Beneath Europa's frozen rind might be an ocean that girdled the entire globe. There was only one known place in the solar system where such conditions prevailed, and that was in the icy waters beneath Earth's North and South Poles. And those waters, the researchers in the JPL imaging room knew, fairly teem with life.

"The Antarctic," someone in the room murmured to himself. "I'm looking at the Antarctic."

Copyright © 1999 by Jeffrey Kluger

Meet the Author

Customer Reviews

Average Review:

Write a Review

and post it to your social network


Most Helpful Customer Reviews

See all customer reviews >