When you think of the 1950s, you might recall the decade's contributions to popular culture: Rock n' Roll, hula hoops, and horror films featuring a menagerie of giant radioactive beasts. Long after Godzilla is forgotten, however, the fifties will be remembered as the dawn of the space age.

For space exploration, the fifties were a time when fantasy changed to reality. At the start of the decade, space travel was something that existed only in the pages of science fiction, the kind of thing most people didn't talk about in serious tones. By its end, a newly-created U.S. space agency was selecting pilots for real space voyages.

At first glance, it might seem that inspiration -- a love of exploration, a fascination with the unknown -- was at the heart of this dramatic change. And it is true that the fifties were ripe with inspiring writings about worlds beyond. A series of articles in Colliers magazine, beginning in 1952, offered fantastic visions of humanity's future in space, written by experts in the field and illustrated with stunning works by such artists as Chesley Bonestell and Fred Freeman. The opening installment in the Colliers series declared, "Man Will Conquer Space Soon."

Such presentations served to raise the American public's awareness that such things were going to happen -- but would they happen as quickly as Colliers promised? In 1952, no one would have guessed that only five years remained before the first Earth satellite would be launched, and only seven before the nation's first astronauts would be named. The reason those developments came as soon as they did -- and the force behind the fifties' push into space -- was the Cold War.

The years after World War 2 were marked by growing tensions between the United States and the Soviet Union. Soon after the war ended, both sides engineers who knew how to build large, liquid-fueled rockets. And the U.S. monopoly on nuclear weapons ended in 1949, when the Soviets tested their first atomic bomb. By the early 1950s, the U.S. and U.S.S.R. were working to merge these technologies in a terrible new weapon, the Intercontinental Ballistic Missile (ICBM).

Until very recently, most historians believed the Soviets got there first.

A brilliant engineer named Sergei Korolev led the Soviet ICBM effort, and his team created a powerful new booster, officially designated R-7, but known to Korolev's team by its Russian nickname Semyorka ("number seven"). It stood almost 100 feet high and developed 880,000 pounds of thrust at liftoff. In August 1957, Semyorka flew to its full range of almost 4,000 miles (2480 kilometers) -- enough to qualify it as an intercontinental rocket. But the dummy warhead at the rocket's nose was destroyed during reentry into the Earth's atmosphere. The Soviets made no mention of mishap in their public statements. However, such problems would continue to plague the Russian ICBM effort until December 1959, when the R-7 was declared an operational weapon. The Americans, meanwhile, made a successful test of their own ICBM, called Atlas, in late 1958.

The ICBM was only part of Korolev's efforts. Korolev had bigger dreams: He wanted to explore space. Under Korolev's direction, Semyorka was became the world's first satellite launcher. On October 4, 1957, it sent the first satellite, Sputnik, into orbit.

Sputnik's bleeping electronic cry, heard by amateur radio operators around the world, announced that the Soviets had scored not only a scientific achievement, but a strategic one. If they could put a satellite in orbit -- and especially the 1,121-pound (2,466-kilogram) Sptunik 2, which carried the first space passenger, a dog, in November 1957 -- then they could loft a nuclear warhead into orbit, where it could threaten any American city. This was already clear after the R-7's test launch in August, but it was only after Sputnik that the American public took the threat seriously.

Spurred in part by the public and media reactions to Sputnik, which bordered on hysteria, U.S. President Dwight Eisenhower stepped up plans for the first U.S. satellite, which had been scheduled for launch as part of the 1958 International Geophysical Year. The first attempt, using a booster called Vanguard, ended in failure on December 6, 1957; the rocket rose only a few feet, then sank back to Earth and exploded.

Now hope rested with the U.S. Army's rocket team, headed by Wernher von Braun, who had led the development of the V-2 missile in Nazi Germany. Von Braun's rocket, called Jupiter C, successfully launched Explorer 1 on January 31, 1958. The U.S. had joined the "space race."

But the Soviets held the lead. In January 1959, after several launch failures, they fired a small probe, called Luna 1, past the moon, missing it by about 3,100 miles (5,000 kilometers). Then, just past midnight, Moscow time, on September 14, the Soviets' Luna 2 struck the lunar surface, becoming the first artificial object to reach another celestial body. And in early October, Luna 3 swung around the moon and sent back the first pictures of its hidden face.

The Americans, meanwhile, suffered a series of embarrassing failures with their Pioneer spacecraft, which were designed to explore the moon's environment. Most failed to escape Earth orbit; more than one blew up before reaching space. Pioneer 4, launched in March 1959, was able to achieve lunar distance, missing the moon by 37,500 miles (60,500 kilometers).

Even as the two superpowers lobbed robotic spacecraft at the moon, the space race was becoming an even higher-stakes game. In April 1959 seven pilots were selected by the newly created National Aeronautics and Space Administration as astronauts for Project Mercury, the U.S. effort to put a man in orbit.

The Soviets, meanwhile, were training their own crop of space fliers, called cosmonauts, who also hoped to be the first into space.

In the coming decade, astronauts and cosmonauts would set their sights on historic journeys in space -- not only into Earth orbit, but to the moon.

Anatoly Zak and Eric Hartwell contributed to this article.

For America, the 1960s begin on an anxious note. Many in the U.S. feared the nation was lagging dangerously behind the Soviet Union in development of Intercontinental Ballistic Missiles (ICBMs). In reality, secret photos from American spy satellites were about to confirm what high-flying aircraft had already shown: the so-called missile gap was not real.

But the Eisenhower administration could not reveal this knowledge to the public, and in 1960 John Kennedy won the presidency over Eisenhower's Vice President, Richard Nixon, partly on the strength of his stance on the missile gap.

When it came to space exploration, no one could be sure how much Kennedy would improve on his predecessor's lukewarm attitude. Within months after entering office, however, Kennedy had no choice but to focus on human spaceflight.

On April 12, 1961, the Soviets launched a 27-year-old fighter pilot named Yuri Gagarin on the world's first piloted space mission. In his spacecraft Vostok ("east"), launched atop a converted R-7 missile, Gagarin made a single orbit of the Earth, returning 108 minutes after liftoff.

The Soviets did not reveal that the Vostok had suffered a malfunction prior to reentry that almost killed Gagarin. When the cosmonaut returned unharmed and exhilarated by his flight, the Soviet Union had scored another key space victory.

For the young American president, Gagarin's flight came as a serious blow.

In Kennedy's mind, competition with the Soviets in space had become vital to U.S. international prestige. On May 5, a former Navy test-pilot named Alan Shepard -- judged by many to be the best pilot among the Original Seven astronauts -- became the first American in space.

Inside his tiny Mercury spacecraft, which he named Freedom 7, Shepard rode a Redstone booster on a 15-minute suborbital flight. The nation reacted to Shepard's feat with wild enthusiasm, and Kennedy took notice.

Kennedy had already been thinking about how to pull ahead of the Soviets in space. He'd asked his advisors to come up with a project that would give the U.S. a clear victory.

Less than three weeks after Shepard's flight, speaking before a joint session of Congress, Kennedy made an announcement that would have seemed unthinkable just years before: "I believe this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth."

Many who heard these words -- including some at NASA -- wondered if Kennedy's challenge was realistic. (A few even wondered if Kennedy had lost his senses.) But it didn't take long for the space agency to begin figuring out how to achieve it.

Meanwhile, the space race sped onward with ever more ambitious flights.

John Glenn -- the astronaut who seemed to step most easily into the role of American hero -- became the first American to orbit the Earth on February 12, 1962. Inside his Friendship 7 spacecraft Glenn circled the globe three times, marveling at the beauty of orbital sunrises and sunsets before sweating through a fiery reentry into the Earth's atmosphere.

Three more astronauts followed Glenn into orbit; in May 1963 the sixth and last piloted Mercury mission saw Gordon Cooper spending more than a day in space.

As important as these missions were for the U.S. program, they were overshadowed by the Soviet Vostok flights. Cosmonaut Gherman Titov made the first day-long flight in 1962. Andriyan Nikolayev in Vostok 3 and Pavel Popovich in Vostok 4 staged the first dual space flight in 1963. Also in 1963, a former cotton mill worker and parachute jumper named Valentina Tereskhkova became the first woman in space, logging almost 3 days in Vostok 6.

And the Soviet firsts didn't end there. Under pressure from Soviet premier Nikita Kruschchev, chief space designer Sergei Korolev staged another orbital "spectacular." The Americans were planning their two-man Gemini flights, but Korolev upstaged Gemini's planned debut by launching three cosmonauts in a "new" spacecraft called Voskhod ("sunrise").

In reality, Voskhod 1 was nothing more than a converted Vostok. Only by taking the dangerous step of denying the cosmonauts ejection seats and space suits was Korolev able to achieve the feat. Fortunately, Voskhod 1 flew without mishap.

But that wasn't true for the Voskhod 2 team of Pavel Belyayev and Alexei Leonov, who made their day-long mission in March, 1965.

Early in the flight, a space-suited Leonov wriggled into a narrow, inflatable airlock attached to the Voskhod's cabin, leaving Belyayev to pilot the ship. Leonov then emerged into the void and spent several minutes floating free, in history's first space walk.

Leonov almost didn't live to tell the tale: In the vacuum of space his suit ballooned dangerously, making it almost impossible for him to get back inside. Only by releasing some of his suit's air -- an almost desperate measure, considering the risk of decompression sickness -- was the exhausted cosmonaut able to re-enter the cabin.

Once again, the world was not told of these difficulties, and Leonov's feat seemed to leave the U.S. program in the dust. But it would not be long before the Americans caught up.

Even as the Soviets racked up one space first after another, NASA was getting closer to the first piloted Gemini missions. Launched by a converted Titan 2 missile, Gemini was the most sophisticated spacecraft yet created. Gemini astronauts would utilize an onboard computer. And they would be able to change their orbit -- something no Soviet crew had yet accomplished.

For NASA, Gemini would serve as a bridge between the relatively simple Mercury flights and the awesome challenge of the Apollo moon program.

In just 20 short months between March 1965 and November 1966, 10 Gemini crews pioneered the techniques necessary for a lunar mission.

They made space walks, some lasting more than two hours. They spent a record-breaking 14 days in space -- the expected duration of a lunar landing flight -- in a cabin no bigger than the front seat of a Volkswagen. (One astronaut later called the two-week Gemini 7 flight "the most heroic mission of all time.")

They mastered the arcane complexities of orbital mechanics to achieve the first rendezvous between two spacecraft in orbit, and the first space docking. And they made the first controlled reentries into the Earth's atmosphere.

To be sure, the Gemini missions had their harrowing moments, none more so than when Gemini 8 astronauts Neil Armstrong and Dave Scott barely escaped disaster when one of their maneuvering thrusters malfunctioned, causing their spacecraft to tumble wildly through space.

And several spacewalkers had their own difficulties -- working in weightlessness was trickier than NASA expected, and more than one sortie had to be cut short when an astronaut became exhausted. Despite these problems, Gemini was considered a tremendous success. It gave the United States the lead in the space race, which was about to become a moon race.

Meanwhile, the Americans and Soviets were extending humanity's reach beyond Earth orbit by means of ever more sophisticated robotic probes. The U.S. Mariner 2 became the first interplanetary spacecraft when it flew past Venus in 1962 and sent back data about this cloud-hidden world. Another American craft, Mariner 4, took the first closeup pictures of Mars in 1965.

Closer to home, in 1966, the Soviet Union achieved the first soft landing of a spacecraft on another world, when Luna 9 came to rest on the moon's Ocean of Storms and sent back images of its dusty surface.

Also in 1966, U.S. Surveyor landers began exploring the lunar surface, and a series of Lunar Orbiter spacecraft began a detailed photo-reconnaissance of the moon from orbit. These missions not only advanced scientific understanding of Earth's nearest neighbor; they helped pave the way for the piloted missions that would follow.

By 1967, both the United States and the Soviet Union were ready to test the spacecraft they would use to send humans to the moon. In the process, both countries suffered devastating failures.

On January 27, 1967, the crew of the first piloted Apollo mission -- veterans Gus Grissom and Ed White, and rookie Roger Chaffee -- perished when a flash fire swept through the sealed cabin of their Apollo 1 command module. NASA's investigation of the tragedy revealed numerous technical flaws in the craft's design, including the need for a quick-opening hatch, and fireproof materials in the cabin. The fire would ultimately delay the Apollo program for more than 20 months.

Disaster struck the Soviets in April 1967, when cosmonaut Vladimir Komarov piloted Soyuz 1 ("union"), an Earth-orbit precursor of a planned lunar-orbit vehicle. When Komarov's flight was plagued by malfunctions, controllers ordered him to come home early. But the craft's parachute did not deploy properly, and Soyuz 1 slammed into the Earth at tremendous speed, killing Komarov. The Soviets too had found that winning the moon race could exact a terrible price.

For the Americans, at least, 1967 ended on a triumphant note with the debut of the giant Saturn 5 moon rocket. Towering 363 feet above its launch pad, the Saturn's three stages contained as much chemical energy as an atomic bomb.

When it lifted off on November 9, with 7.5 million pounds of thrust, the Saturn's fire and thunder were truly awesome to behold. For NASA, the Saturn 5's flawless test flight marked a key milestone on the road to the moon.

Americans returned to space on October 11, 1968, when the crew of Apollo 7 made an 11-day Earth-orbit test of the Apollo command and service modules, which had been redesigned in the wake of the fire.

The flight went so well -- one mission controller dubbed it "101 percent successful" -- that NASA decided to take a stunningly bold step with Apollo 8: its crew would orbit the moon.

There was a note of urgency in the plan: Intelligence reports showed that the Soviets, who had recovered from the loss of Soyuz 1, were planning to send two cosmonauts on a circumlunar flight before the end of the year.

But after two unpiloted circumlunar test flights experienced malfunctions in the fall of 1968, Soviet officials refused to give the go-ahead for a piloted mission.

The way was clear for the Apollo 8 crew -- Frank Borman, Jim Lovell, and Bill Anders, to make history.

On December 24, 1968, after a 66-hour journey across 230,000 miles of space, the three men fired their spacecraft's main engine to go into lunar orbit. They remained there for 20 hours, making navigation sightings, taking photographs and beaming live television pictures back to Earth, before returning home.

After a reentry at 25,000 miles per hour -- faster than humans had ever traveled -- Borman's crew splashed down safely in the waters of the Pacific.

Apollo 8 was more than a technical triumph, more even than a milestone in exploration: It was a mountaintop experience for the entire human species. A single photograph from Apollo 8, showing the Earth rising beyond the moon's barren horizon, became one of the century's most famous and inspiring images.

For the Soviets, Apollo 8's success was a stinging defeat that seemed to take the wind out of their own moon effort, at least temporarily. For NASA, it had the opposite effect. Now the way was clear to attempt the lunar landing. If all went well on Apollos 9 and 10, Apollo 11 would try for a landing the next summer. But that was a big "if"; each mission ranked as one of the most complex and difficult space missions ever attempted.

Amazingly, both Apollo 9 -- an Earth-orbit test of the entire Apollo spacecraft -- and Apollo 10 -- a "dress rehearsal" for the landing in lunar orbit -- were almost flawless.

When Apollo 10 splashed down on May 26, Neil Armstrong and his Apollo 11 crew had less than two months left to prepare for the ultimate test flight.

July 16, 1969 dawned clear and hot for the spectators (estimated at a million people) who flocked to Cape Kennedy for the Apollo 11 launch.

They were not disappointed.

At 9:32 a.m., the Saturn 5 came to life, its fire akin to a second sun, its roar shattering the morning stillness as it sent Armstrong and crewmates Buzz Aldrin and Mike Collins on history's third lunar voyage. Three days later the men arrived in lunar orbit, knowing that their real mission -- the landing attempt -- was about to begin.

On July 20, Armstrong and Aldrin, clad in their space suits, took their places in the tiny cabin of the Lunar Module Eagle, leaving Collins to pilot the command ship Columbia. The two ships separated, and with a blast from their lander's descent engine, Armstrong and Aldrin began their trip down to the moon's Sea of Tranquillity.

At 50,000 feet they ignited Eagle's engine once more, beginning the landing's final phase, called the Powered Descent. Everyone knew there could be problems, and there were: On the way down, an overloaded computer threatened to abort the mission; only quick thinking by experts in mission control allowed Armstrong and Aldrin to continue.

A thousand feet above the moon, Armstrong saw that the craft was heading for a crater the size of a football field that was rimmed with boulders as big as automobiles.

Taking control, he steered Eagle to a clear spot and brought the craft into a vertical descent, while Aldrin called out the diminishing altitude. With his fuel supply running low, Armstrong struggled to see his landing spot through a storm of moon dust kicked up by the descent engine.

Finally, a blue light on the instrument panel signaled that three metal probes on Eagle's footpads had touched the moon.

"Contact light," announced Aldrin. Eagle settled gently onto the dusty lunar ground, and Armstrong shut down the engine. The two men turned to each other and shook hands in a brief moment of celebration.

Then Armstrong radioed to a waiting Earth, "Houston, Tranquillity Base here. The Eagle has landed."

Almost seven hours later, Armstrong emerged from Eagle. After descending the ladder on the craft's front landing leg, he planted his left foot on the ancient dust of the Sea of Tranquillity, and declared: "That's one small step for [a] man, one giant leap for mankind."

Minutes later, Aldrin joined him on the surface, and for a bit less than two hours, the two men collected rocks, planted the American flag, and took pictures.

They also experienced the delights of moving in the moon's one-sixth gravity, and marveled at the beauty of the utterly pristine, utterly ancient lunar landscape. Then it was time for history's first moonwalk to end, as the astronauts climbed back into their lander for a fitful rest.

On July 21, the moment of truth for Armstrong and Aldrin was at hand: the firing of Eagle's ascent rocket to return them to lunar orbit, and a reunion with Collins. Everyone, on Earth and in space, knew that the engine had to work, or Armstrong and Aldrin would face a lonely death on the moon.

When the prescribed moment came, Aldrin pushed a button on the onboard computer, and after a brief moment, the engine ignited with an invisible flame. Amid a spray of insulation, Eagle ascended like a super-fast, silent elevator, heading for a rendezvous with Columbia. Apollo 11's safe return on July 24 marked the beginning of a new age, one in which human beings could truly be called a spacefaring species.

For NASA, the age of lunar exploration was only beginning: More landings were ahead, including Apollo 12's pinpoint lunar touchdown in November.

The United States had won the moon race. But the 1970s would bring a change of fortunes for the space agency, while the Soviet Union blazed a new trail, as pioneers of long-duration space missions.

For NASA, the sixties had ended in triumph: Humans had walked on the moon, and NASA had put them there. For the space agency, the success of the first lunar landing was an invitation to dream even bigger dreams. NASA administrator Tom Paine and his deputies planned a stunning array of space activities so extensive that they would live up to the vision presented in Collier's magazine in the 1950s. There would be space stations in Earth orbit, a base on the moon, and human missions to Mars.

But these dreams were met by a new, harsh reality: the 1960s "heyday" for space budgets was over. National priorities had shifted since John Kennedy had challenged the nation to a lunar landing by decade's end. The country was preoccupied with an ongoing struggle for civil rights and dissent over the war in Vietnam. The booming economy of the early 1960s had given way to concern over inflation. Space exploration no longer headed the Cold War agenda. And so, when the Nixon administration responded to NASA's budget requests, Paine's grand vision fell by the wayside.

Only one element of the plan was preserved by the White House and Congress: A reusable space shuttle that would ferry astronauts to and from Earth orbit. The shuttle would launch satelllites, and serve as an orbiting research platform. And NASA promised it would lower the high cost of access to space.

The shuttle would not be ready to fly until 1978 at the earliest. Meanwhile, a program called Skylab would serve as a follow-on to Apollo. With Skylab, an Earth-orbit space station constructed largely from spare Apollo hardware, astronauts would go from visiting space to living there. With as much living space as a small house, Skylab crews would spend up to three months operating astronomical telescopes to study the Sun, special cameras to photograph the Earth in selected wavelengths of light, and other experiments designed to study the behavior of materials in weightlessness. The astronauts would also study themselves with a slew of medical experiments.

Meanwhile, the Apollo moon missions continued to rack up extraordinary accomplishments. Simply getting to the moon and back had been the goal of the first Apollo landing crew. But beginning with Apollo 12, the mission began to emphasize scientific exploration. In November 1969 Apollo 12 astronauts Pete Conrad and Alan Bean had made history's first pinpoint lunar landing by touching down within walking distance of the robotic Surveyor 3 probe, which had rested on the moon's Ocean of Storms since early 1967. In the process, they had demonstrated that future Apollo crews could set down at some of the most geologically enticing places on the moon.

Scientists' hopes were high for the Apollo13 mission which left Earth on April 11, 1970, bound for the moon's Fra Mauro highlands. But those hopes evaporated some 55 hours into the mission, when an oxygen tank exploded aboard the Apollo 13 service module, aborting the flight and plunging NASA into the worst crisis it had ever faced on a piloted space mission.

Aboard the crippled spacecraft, lunar veteran Jim Lovell and his rookie crew, Jack Swigert and Fred Haise, were forced to abort their mission and begin an emergency trip home. To survive, they used their lunar lander as a lifeboat, utilizing its oxygen, radio, and rocket engines. By the time they reached Earth four days later, the men were exhausted and battling bone-chilling conditions aboard their spacecraft. But the combined efforts of the astronauts and hundreds of flight controllers and engineers on Earth paid off: Lovell's crew splashed down safely on April 17, crowning a recovery effort that many called NASA's finest hour.

Picking up the torch from Jim Lovell's crew, Apollo 14 was led by America's first space traveler, Alan Shepard, who had been grounded since his 1961 Mercury mission by an inner-ear disorder, but restored to health after an experimental surgery. Shepard's footsteps on the Fra Mauro highlands represented not only a success for NASA, but a personal triumph.

In the summer of 1971, Apollo's scientific phase got into high gear, as Apollo 15's Dave Scott and Jim Irwin became the first astronauts to explore the mountains of the moon. They brought along a new innovation: a battery powered car called the Lunar Rover that allowed them to range for miles across the landscape on geologic "treasure hunts."

For three days, Scott and Irwin lived and worked among the moon's Apennine mountains. Among their finds was a rock that dated back 4.5 billion years, almost as old as the moon itself, which became known as the "Genesis rock." Meanwhile, circling the moon, crewmate Al Worden operated a battery of scientific cameras and sensors in an intensive orbital reconnaissance.

Even as Apollo 15 demonstrated the new heights Apollo had reached, budget cuts were bringing the program to a premature end. In 1970 three lunar missions were canceled, leaving only Apollo 16 and 17 to write the final chapters in the Apollo saga.

In December 1972, Apollo 17 saw Gene Cernan and geologist-astronaut Jack Schmitt -- the first professional scientist to visit another world -- explore the spectacular Taurus Littrow valley, while Ron Evans surveyed the moon from orbit. When Apollo 17 splashed down in the Pacific, the 20^th century's brief era of human exploration of the moon was over.

By the early 1970s, the Soviet Union was forced to abandon its efforts to send people to the moon. Even before Apollo 11's lunar landing, Soviet space planners had realized they would likely lose the moon race. They had begun their lunar program relatively late, a few years after the Americans.

But the most severe blow came from the failure of Sergei Korolev's giant N-1 moon rocket: It exploded during each of its four test-launches between 1969 and 1972. Some still dreamed of catching up with the U.S. program, or even surpassing it, by establishing a lunar base. But the repeated failures of the N-1 put an end to such plans. Korolev wasn't around to see his dream abandoned; he had died during surgery in 1966.

As an alternative, the Soviets staged a series of robotic missions in an attempt to show the world that they could duplicate Apollo's scientific harvest, for a fraction of the cost. The first tries at an automated lunar sample-return came before Apollo 11. But success did not come until September, 1970: Luna 16 touched down on the Sea of Fertility, drilled into the soil, and launched a return capsule to Earth bearing a small vial of lunar dust and rock fragments. Luna 20 repeated the feat in 1972, and Luna 24 retrieved a sample from the Sea of Crisis in 1976.

The Soviets also deployed a pair of automated rovers which roamed the moon under remote control by engineers on Earth. Named Lunakhod, the rovers were equipped with television cameras and scientific instruments to investigate the properties of lunar soil. Lunakhod 1 reached the Sea of Rains in 1970; Lunakhod 2 traveled the Sea of Serenity in 1973.

Beginning in the early 1970s, the Soviets' human spaceflight program charted a new course, into Earth orbit. In 1971, two years before NASA's initial Skylab mission, they launched the world's first space station, Salyut 1. Three cosmonauts spent 21 days aboard the station, but their mission ended tragically: All three men died after a sudden loss of cabin pressure immediately before their spacecraft made an automatic reentry. Ground teams rushed to the craft only to find the crew dead inside.

By September, 1973, the Soviets had recovered from the tragedy and were back to launching Salyuts for scientific missions. They also inaugurated a series of Almaz space stations for military reconnaissance, further evidence that the Cold War was being waged in space as well as on Earth.

The Salyut missions put the Soviet Union at the frontier of long-duration spaceflight. With a four-month residence on Salyut 6 in 1978, the crew of Soyuz 29 broke the U.S. space endurance record set aboard Skylab. The following year Soyuz 32 cosmonauts Vladimir Lyakhov and Valeri Ryumin cosmonauts logged an extraordinary stay of six months the station. Even that record would be surpassed as the Soviet space marathons continued into the 1980s.

International space activities blossomed in the 1970s. Beginning in 1973, ten European nations joined forces to form the European Space Agency, or ESA. ESA's members embarked on a variety of space projects, including development of a new satellite launcher called Ariane. The first successful Ariane launch in 1979 ushered in a new era of commercial space activities.

Also in 1975, détente found its way into space, if only for a moment, as the U.S. and Soviet Union staged a joint space mission called the Apollo-Soyuz Test project. The dual mission, which commanded by Apollo veteran Tom Stafford and Soviet spacewalker Alexei Leonov, featured the first international space docking.

The 1970s also saw a growing number of nations launching satellites. China's first, lofted in 1971, broadcast a melody entitled "East Is Red." India, whose first satellite was launched by the Soviets in 1975, achieved its own satellite launch in 1979.

In the 1970s, planetary exploration flourished as U.S. and Soviet robotic missions sent back a phenomenal haul of data. Mars was the target of the Mariner 9 spacecraft, which began mapping the planet from orbit in 1971. Mariner's images revealed towering volcanoes, giant canyons, and winding valleys that appeared to be dry river beds. In 1976, the twin Viking landers made the first successful touchdowns on the martian surface, sending back images and data on the planet's atmosphere and soil. The Vikings' most celebrated experiment -- a search for signs of microbial life -- failed to find any conclusive evidence.

The Mariner 10 spacecraft was the first to take advantage of a technique called gravity assist: During a flyby of Venus, the probe used the planet's gravity to redirect it toward Mercury. Thanks to a lucky coincidence between Mercury's orbital period and the spacecraft's trajectory, Mariner 10 made not one but three flybys of the innermost planet.

The Soviets, who had little success in several Mars landing attempts, succeeded with an even more challenging task: Their Venera landers actually survived a descent to the hellish surface of Venus. Beneath the planet's dense, opaque atmosphere, the Venera's found surface pressures 90 times that on Earth, and temperatures as high as 900 degrees Fahrenheit -- hot enough to melt lead. The Venera landings gave scientists their first images and in situ data on the planet's surface composition. But in the 1970s, Venus was the only truly successful target for Soviet planetary missions.

The United States, meanwhile, turned its attention to the outer solar system with the Pioneer 10 and 11 spacecraft. These twin probes made the first flybys of Jupiter and Saturn, sending back valuable glimpses of these planets' cloudy atmospheres, and valuable data on their powerful magnetic fields. The more sophisticated Voyager 1 and 2 probes, launched in 1977, began their own "grand tour" of the outer solar system, a mission that would ultimately stretch to the end of the 1980s, and even beyond.

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