This New Ocean, page 73
The “Peace” Plaque
Knowing that both Pioneers would keep going forever unless they collided with something, and taking it as an article of faith that there is intelligent life out there somewhere, gold-anodized aluminum plaques designed by Sagan, Frank Drake, Sagan’s colleague at Cornell, and Linda Sagan, were attached to both Pioneers’ buses. Each showed Earth’s place in the solar system from which it came, a silhouette of the vehicle itself, when it was launched, a diagram representing fourteen pulsars that were arranged to show a scientifically literate being where the home star of this system was located, and a naked man and woman. The man’s right hand was raised as a sign of peace. The woman stood passively beside him.
Whatever other life-forms would make of the two earthlings, they created a storm of controversy on their own planet. The print and television media were confounded by the problem of showing naked people to American families. The Chicago Sun-Times reacted by airbrushing out the couple’s genitals and her breasts. The Los Angeles Times was barraged with letters denouncing the space agency for using taxpayers’ money to send smut to space. Outraged feminists complained that the woman was placed slightly behind the man, did not have a hand up, and looked at him with apparent adoration that they insisted amounted to submission. The message that the male-dominated, macho NASA wanted to send to the farthest reaches of the universe, the angry women charged, was that their own sex was subservient. Still others protested that whoever was dominant, the couple represented a very limited group of humans and that, as a British editorial put it, future plaques ought to be designed by a large international ecumenical group of scientists and laypeople. The uproar over the plaque said as much about life on Earth as what it depicted.
The man’s peace gesture could conceivably be taken seriously by extraterrestrials. But the spirit of cooperation it tried to convey was stubbornly ignored by Ames and JPL mission planners who were forced to work together. Headquarters had insisted when it assigned Pioneer Jupiter Saturn to Ames not only that JPL handle tracking and communication through the Deep Space Network, but that its experienced navigators help plan the trajectories as well. While the DSN had to be used for all deep-space missions, Hall immediately objected to the part about trajectory planning for what he would later call in absolute candor “competitive” reasons. Ames, after all, was moving into JPL’s domain—hostile territory—and felt protective of its important and glamorous mission. At the same time, it rankled the brats of Pasadena that fate—no, headquarters—had awarded the first missions to Jupiter and Saturn not to the institution that had given the world Explorer 1, Ranger, Surveyor, and Mariner but to the upstarts upstate. For its part, headquarters had better things to worry about than a family feud in California. Hall was therefore overruled and ordered to go down to Pasadena and confer with Parks, JPL’s senior guidance man, and anyone else who could help get the Pioneers to their destinations.
The sticking point was that neither side wanted to take responsibility for certain phases of the mission, Hall would recall years later. “God, I’ve never seen four guys who distrusted each other more in my life,” he would say, laughing heartily. “They didn’t trust us and we didn’t trust them. It was like a couple of Arabs trying to sell a dead camel to each other.” In the end, though, the relentless pressure of the 1972 window forced a reconciliation of sorts.
By Jupiter
Pioneer F, now renamed Pioneer 10, flew into the asteroid belt in mid-July 1972 and came out unscathed the following February. Seeing that its predecessor had suffered no damage during its seven-month passage, NASA launched Pioneer G, soon renamed Pioneer 11, on April 5, 1973. JPL’s Mariner 10 left for Venus and Mercury on the first two-planet mission on November 4 of the same year. Meanwhile, the lab was also gearing up for Mariner Jupiter Saturn. What would soon be called the “golden age of planetary exploration” was under way.
Jupiter has undoubtedly exhilarated every astronomer since Marius and Galileo. It is a glorious sight seen through a telescope against the blackness of night: a spinning colossus of multicolored bands capped by gray hoods that crown both poles. A Great Red Spot larger than Earth was reported in the 1660s by both Robert Hooke, an English scientist, and Giovanni Cassini, the Italianborn director of the Paris Observatory who ensured his place in history by discovering four of Saturn’s moons and a great deal about its spectacular rings.
The king of the sky is the dominant planet in this solar system and by itself accounts for two thirds of all planetary matter. It has 1,317 times the volume of Earth, but weighs only 318 times as much, meaning that it is made of something considerably lighter than the home planet’s rock and iron. That something, which was revealed by analyzing its radiation through telescopes long before the planetary missions, is compressed hydrogen and helium, the two most abundant gases in the universe, and some methane and ammonia. Both of the first two elements are in roughly the same proportion as they are in the Sun, making Jupiter slightly denser than water. In fact, astronomers have calculated that if Jupiter had been a hundred times the size it is, it could have become a sun. And Marius’s and Galileo’s telescopes had spotted the first four moons at the dawn of telescopy. Eight more had been added to the original Jovian four by the time Pioneer 10 arrived, and there was every possibility that still others would show up during the encounter. (A NASA news release issued in February 1972 said that Jupiter “has 12 moons.” That is a statement no serious scientist would have endorsed, since new objects are always turning up in space. “Has 12 known moons” is the way the cautious astronomers would have put it.)
Sagan, as cautious as the next astronomer, was haunted by Jupiter. “It is apparently radiating to space more energy than it is receiving from the Sun, energy perhaps derived from a continuing slow gravitational contraction like that which characterized the Sun before it became capable of thermonuclear reactions,” he had said in a lecture in Oregon in 1970 that reflected his frustration. “Visual observation of Jupiter show its clouds to be in seething turbulence. Bubbles float to the cloudtops from the interior and are torn apart by the rapid rotational shear forces. These varying belts and bands and spots in the clouds are marked by an enormous variety of delicate and vivid hues. What are the molecules responsible for this coloration?”
The “Life” Card
Not to leave any possibility of making the morning papers and evening news unexploited, the space agency’s public affairs specialists even played the “life” card. The fact that the planet was a mass of deadly radiation did not prevent those who wrote the Pioneer handouts from holding out the possibility that Jupiter, like Mars, just might contain the constituents of life. “Perhaps the most intriguing unknown is the possible presence of life in Jupiter’s atmosphere,” a hefty press kit issued on February 20, 1972, suggested. “Jupiter’s atmosphere contains ammonia, methane, and hydrogen. These constituents, along with water, are the chemical ingredients of the primordial ‘soup’ believed to have produced the first life on Earth by chemical evolution.”
And since Jupiter was known to have an internal heat source, the release continued, “many scientists believe that large regions below the frigid cloud layer are around room temperature.” Jupiter, the writer therefore concluded, “could contain the building blocks of life.” But even if the building blocks were there, it would in no way have shown that there was life in the massive, swirling poison factory. Europa, one of the Galilean moons, was a far more likely candidate to harbor life in some primitive form because it had a real water ocean and a possible inner heat source. But in 1972 there was no way of knowing that.
Tweaking the Dragon’s Tail
Having survived dangers of its own, including a near blinding of the photopolarimeter by the Sun, and then having broken virtually every long-distance space record, Pioneer 10 began its near encounter on November 3, 1973.* During the next twenty-six days, the speeding spacecraft crossed the paths of all seven of the outermost of Jupiter’s known moons and was plowing into its fearsome radiation belts. By then it had also penetrated Jupiter’s massive bow shock, where the solar wind runs into the planet’s magnetic field and separates like water flowing past both sides of a ship’s bow. All this and much more poured into Ames via the Deep Space Network. As always happened at encounters, the tightly lidded science and engineering played counterpoint to raw emotion as the explorers at Ames reveled in the history they were making.
“We are really only twelve generations away from Galileo and his first crude look at the planet,” an exhilarated, almost disbelieving Charlie Hall told reporters in the main auditorium. “Twelve generations later, we are actually there, measuring many of the characteristics of the planet itself,” Pioneer’s project manager added as he and his spacecraft sped together toward the gigantic ball of storms. Hall, amazed at the wonder of it all, had just found a place for himself in the annals of time.
At first the images that came back from the photopolarimeter in real time were no better than those taken through telescopes. By December 2, the day before closest approach, they began to surpass anything taken from Earth. The pictures showed not only a growing planet, but Io and Ganymede as well. Pioneer 10’s closest approach to Jupiter came within one minute of schedule, with the spacecraft slicing between the planet and Io for an occultation: in effect silhouetting part of Io in a radio beam to Earth that would provide data on the moon’s size and the thickness of its atmosphere, if it had one.
By that time, Pioneer 10 was working its mechanical heart out as it slammed into radiation so intense that two of its cosmic-ray detectors became saturated. Others, specially designed to contend with that problem, continued to measure the proton flux around the planet while ultraviolet measurements were recorded and infrared readings were taken of Io. Meanwhile, twenty-three more images were taken of Jupiter, Io, Callisto, and Ganymede.
Less than three hours before closest approach, Pioneer 10 began an hour’s imaging of the enigmatic Great Red Spot. The pictures would be the first to suggest that the huge area of turbulence might be a massive storm. They and others were good enough, and were shown to reporters quickly enough, to earn the Pioneer program an Emmy award from the National Academy of Television Arts and Sciences.
The closest approach came at 6:26 P.M. Pacific Standard Time on December 3 as Pioneer 10 skimmed over Jupiter’s cloud tops at an altitude of only 81,000 miles. The elated scientists who were running the robot’s particles and fields experiment saw that their detector had run into a clearly defined barrage of particles, suggesting that what had long been surmised was probably true: Jupiter had its own rings. Meanwhile, the planet’s atmospheric composition, temperature structure, and thermal balance were being recorded, and so were the temperatures of Io, Ganymede, and Europa.
Then Pioneer 10 suddenly dropped out of sight, disappearing behind Jupiter and causing a sixty-five-minute communication blackout. The tension level at Ames surged even though the break in contact had been expected.
“We watched the PICS [Pioneer Image Converter System, which turned the signals into pictures] image displayed in real-time as the signals came back from the distant planet,” Lyn R. Doose, an imaging experimenter from the University of Arizona, would report. Then “a single bright spot appeared, and then another, until a line gradually built up. We knew we were seeing sunrise on Jupiter as the PICS image showed a crescent-like shape. We survived passage through the periapsis,” the relieved scientist added, grateful that he and his spacecraft had made it safely through the radiation flux. Pioneer 10 was now the first machine from Earth to make it through both the asteroid belt and Jupiter’s blanket of radioactive poison.
“We can say that we sent Pioneer 10 off to tweak a dragon’s tail, and it did that and more,” said a proud Robert Kraemer, who represented headquarters. “It gave a really good yank and … it managed to survive.”
“This has been the most exciting day of my life,” Pioneer 10’s exhausted but exuberant chief scientist, Richard O. Fimmel, added. He spoke for the whole center.
When its encounter with Jupiter was over, Pioneer 10 cruised out of the solar system at about 25,000 miles an hour. Still riding the solar wind, it would cross Pluto’s path early in 1990 and then carry its plaque to interstellar space, all the while reporting what it found on increasingly faint signals that took almost twelve and a half hours to reach home. The power of the signals would be so weak, Fimmel explained, that it would have to be collected and saved for 11 billion years to light a 7.5-watt night-light for a millisecond. And by that time, the Sun would be just another dot of light in the vast galaxy. At last report, it was headed for the star Aldebaran in the constellation Taurus.
There would be a party at Ames in June 1988 to mark the fifth anniversary of Pioneer 10’s crossing Neptune’s orbital path. Someone jokingly asked a representative of the company that had built the tough little record breaker whether it was still under warranty. “TRW’s position,” he answered, “has been that if you bring it back, we’ll fix it.”33
Pioneer 11 could have duplicated its predecessor’s mission, but there were other things to be discovered, and since its predecessor had done so well, it was sent off chasing new possibilities. The second spacecraft to reach an outer planet was therefore ordered to approach Jupiter from its left side and under its southern hemisphere, coming as close as 26,725 miles before hurtling almost straight up and out of the plane of the ecliptic, at least momentarily. It confirmed a great deal of the data sent by Pioneer 10, added information on the Great Red Spot, and provided new details about Jupiter’s immense polar regions. Pioneer 11 returned 460 pictures of Jupiter and its four most famous moons, many taken at angles impossible to get from Earth. Then it looped over Jupiter, raced high above its north pole, and leveled out once more as it headed for its rendezvous with Saturn. It was now called Pioneer Saturn.
Lord of the Rings
Having picked up the predicted assist from Jupiter’s gravity, Pioneer 11 made its closest approach to Saturn on September 1, 1979, after a two-billion-mile trip that took six and a half years. The United States now put yet another planet on its trophy shelf.
During its ten-day encounter, Pioneer 11 skimmed under the famous ring plane twice, coming as close as 1,240 miles, and streaked past the planet itself at a height of only 13,000 miles. The most fundamental discovery was not about the rings, but that Saturn has radiation belts and a strong magnetic field and magnetosphere, both of which had been suspected but unproved.
The probe also discovered a new moon just beyond the edge of the rings and did photopolarimeter measurements of the known moons—Iapetus, Dione, Tethys, Rhea, and Titan—and ultraviolet observations of Hyperion, Rhea, Dione, Tethys, Enceladus, and Titan. In their book The Grand Tour, Ron Miller and William Hartmann took strong exception to what they called the “nine-planet gestalt,” arguing that there are many more individual worlds in this solar system than the officially designated planets.34 It is hard to imagine any scientist disagreeing. Titan, for example, is larger than Mercury and therefore was an irresistible subject for Pioneer 11’s atmospheric, temperature, heat balance, magnetic wake, and other experiments.
Carefully following Pioneer 11’s trajectory as it sailed past Saturn helped project scientists calculate the planet’s shape and gravity more accurately than was possible from Earth. That, together with a temperature profile made from infrared measurements of the heat given off by Saturn’s clouds beyond what was absorbed by the Sun, shed light on its interior. Saturn’s core, roughly the size of eighteen Earths, was suddenly understood to have two distinct regions. There was an iron-rich, rocky inner core encased by a ball of ammonia, methane, and water. No one suggested the possibility that there was potentially life in there, though the possibility that it existed on Titan was mentioned.
While the resolution of Pioneer 11’s imagery was necessarily poor compared to that taken by three-axis-stabilized spacecraft using television cameras, it was good enough to spot two new rings. One, which appeared separated from the A Ring by a gap that was promptly called the Pioneer Division, was named the F Ring.37 At less than five hundred miles across, it was considered “narrow.” The other, named the G Ring, directly adjoined the F Ring and was more than ten times wider.38 There was much more that would take months to sort out.
When Pioneer 11 left Saturn, it headed across the other side of the solar system from its twin at a speed of about 275 million miles a year. Both of them made three fundamental contributions to the exploration of space. Most obviously, they returned a huge amount of new information about the two largest planets in the solar system and the space between them. They also demonstrated that the outer solar system could be safely navigated. And they did indeed find a path for their successors, both of which were already on their way.
Venus Partially Unveiled
While the Pioneers reconnoitered the two big outer gas balls, JPL’s Mariner 10 was looking inward (so to speak). Riding an Atlas-Centaur, it left Florida during the night of November 4, 1973, and had its closest encounter with Venus ninety-three days later as it sailed 3,600 miles over the hot, fog-shrouded sphere.
Whatever else the poisonous mist concealed, it was known to be hiding five Soviet spacecraft (or their scattered remains), one of which, Venera 4, had six years earlier become the first visitor from Earth to transmit data back before it had been crushed by atmospheric pressure at an altitude of seventeen miles. Veneras 5 and 6 had relayed more atmospheric data in 1969 before they, too, had been crushed. Then Venera 7 had made the first soft landing on December 15, 1970, and sent back data for twenty-three minutes. Venera 8, a follow-on soft lander, had repeated the exacting operation in July 1972 with a fifty-minute burst of information showing that Venus was a pressure cooker with a landing-site surface temperature of 860 degrees Fahrenheit and an atmospheric pressure ninety times as great as Earth’s. That, as well as an atmosphere that would prove to be 96 percent carbon dioxide, showed beyond doubt that Venus was uninhabitable by anything that lived on Earth. The heat and carbon dioxide atmosphere would also be used to help model what could happen to Earth if the so-called greenhouse effect went out of control. Soviet scientists had not allowed a single Venus launch window to pass without taking at least one shot at it since planetary exploration had begun. And those shots had been very successful. Now it was the Americans’ turn.
