Oceanworlds

Nineveh remained forgotten until the decisive Battle of Nineveh in 627 AD, where the Byzantine Empire defeated the Persian Empire. This proved ephemeral as the Arab Caliphate soon conquered the entire region and kept it for another millennium.

  The reconstruction of most of the genesis and early history of astronomy and astrology—until recently one and the same—stems from just two broken clay tablets, known by the first two words in their text: the Mul Apin. Unearthed by one Sir Austen Henry Layard in 1847 from the remnants of the Royal Library of Ashurbanipal, many of the Mul Apin contents come all the way from the Sumerians, who invented writing and cities around 3000 BC.

  The olden people’s reverence and obsession with the sky may be perplexing for us contemporaries. Seem impractical. Anything but. The canvas above directly affected their daily life. The Sun’s transit defined the notion of day. The Moon’s rotation over its four phases defined a month. Winter and summer solstice, spring and fall equinoxes defined a year. Sirius, the sky’s brightest star, rising above the eastern horizon just before sunrise marked the flooding of the Nile. As nomadic tribes embraced agriculture, the sky became their guide for planting and harvesting. It hastened the growth of our civilization and its expansion. It told when the easterlies would blow or which season had no trade winds. The three dots of Orion defined the cardinal points and thus guided travelers and sailors. No one ventured across vast oceans without being able to chart their courses against the heavens. Countless stars pinned to the firmament could only provoke our knack for patterns, finding shapes in randomness, hence the twelve zodiacal constellations, or five bright wandering stars that danced across the sky, later known as planets. With this prism, it’s hard not to think that deciphering the skies could help predict the future or determine one’s life course. How could they not see prophecy in a solar eclipse or an unannounced comet traversing the heavens and vanishing as weeks went by?

  Had it not been for that momentous day when something caught the attention of a 25-year-old Alexander—just a week before the most important battle of his life and one of the most decisive in history, heavily outnumbered by Darius III and the Persian Empire—the Mul Apin would stand as the only surviving wisdom from the great civilizations of Mesopotamia, the rest forever lost to the sands of time. Instead, their celestial erudition was adopted almost verbatim by the Greeks, then inherited by the Romans. Thus, Marduk became Zeus and then Jupiter, king of the gods. Ninib became Kronos and then Saturn, Jupiter’s progenitor.

  About 150 AD in Alexandria—by then a Roman province—as Western civilization was plunging toward the Dark Ages, a Greek-born astronomer called Ptolemy produced the Almagest, one of the most influential scientific texts of all time. The mathematical and astronomical treatise on the motion of stars and planets summarized all thinking up to then, becoming indisputable orthodoxy for the next fourteen centuries in both European and Islamic worlds.

  January 10 1610. Galileo Galilei breathed three deep breaths, the latest attempt to bridle a racing pulse conspiring against him, and looked again through the eyepiece of his latest and most powerful cannocchiale telescope. Change was in the air. Ever since Copernicus’ 1543 seminal On the Revolutions of the Celestial Spheres, intellectuals across Europe had been trying to assimilate to the baffling notion that the cosmos didn’t revolve around the Earth. But this revision of the Universe did not sit well with the most powerful institution on the continent, the Catholic Church. Just ten years prior, the Inquisition had burned Giordano Bruno at the stake, the Dominican friar espousing the Copernican model, who had the temerity to propose that stars were distant suns surrounded by their own planets and that the Universe was infinite. Discovery dramatically sped up in June of 1609, when Galileo heard of a device being patented in the Netherlands capable of seeing things far away as if they were nearby. That’s all it took. In a month he had built his own with 3x magnification as a flood of breakthroughs were igniting all around Europe. But tonight, something else was happening. His new telescope had 20x magnification, and what his strained eye was seeing would change history. The thrill of discovery was dizzying, as was the sense of exposure. His renown among scholarly circles in Europe stemmed from his famous experiments on gravity two decades past. But this—this would forever change society, religion, and philosophy. For all of history, planets had been wandering stars, brighter but otherwise indistinguishable from the ones in the background. But three days ago, as he pointed humanity’s most advanced device at Jupiter, he saw for the first time its sheer immensity, along with “three fixed stars, totally invisible by their smallness” by its side. Now, one of them had disappeared and the others had shifted. He closed his eyes and set his thoughts aside, but they came screaming back. The third moon was behind the planet. This demolished Ptolemaic astronomy, whose main principle was that all heavenly bodies should circle the Earth. After six decades, the Copernican evolution had been triggered with the force of a supernova. The scientific revolution that ensued would know no boundaries.

  In Galileo’s mind, his triumph of ingenuity had one dark spot that troubled the great man until his death in 1642. Saturn. The first time he saw it through a telescope in 1610, his excitement was such that he dashed a letter off to his friend, the famous German astronomer Johannes Kepler: “I have observed the highest triple bodied planet system.” The news got to the Austrian emperor Rudolf II, who requested commentary from Galileo. He explained that Saturn wasn’t a single planet but three touching each other. Today, any pair of binoculars can achieve Galileo’s visual feat, with Saturn looking like a small non-circular dot. The conundrum presented itself two years later when the side planets vanished and then reappeared in 1616. The axial tilt of Saturn means twice every Saturnian year—or once every fifteen Earth years—the rings disappear from view as they angle directly edge-on to us. Thus, the obsession with the otherworldly behemoth was born and would never abate.

  Nowadays, a $50 telescope easily goes past the 30x magnification required to see the ring system around Saturn as well as to spot its largest moon, Titan. But it took until 1655 for another polymath, Christiaan Huygens, to solve the mystery that plagued the genius of Galileo.

  By 1684, Giovanni Domenico Cassini had discovered four other moons and the division that separates the main rings. But Saturn’s enormous distance from Earth—more than twice that of the far away Jupiter—meant that besides a few sparse discoveries, the gas giant was shrouded in almost complete mystery all the way to 1979.

  The Exploration of the Outer Solar System

  In a way, NASA’s formation on July 29 1958 echoes the birth of the US Constitution: as Thomas Jefferson in Paris wrote to John Adams in London, the group of people crafting it “really is an assembly of demigods.” As a result, NASA’s long-term plan was brilliant, far-reaching, bold, and in hindsight, clairvoyant. The exploration of the Solar System would be done by (at the time, theoretical) robots in a three-phased approach: i. reconnaissance missions to pass by every planet from the mid-60s to the mid-80s; ii. an orbiters and landers era, which we are currently in; and iii. a sample-return-to-Earth future.

  In 1964—while the Apollo program to put a man on the Moon was in full swing—a 30-year-old NASA aerospace engineer named Gary Flandro discovered a jaw-dropping free lunch. Every 175 years, the alignment of Jupiter, Saturn, Uranus, and Neptune enables a single spacecraft to visit them all. The once-in-many-lifetimes Grand Tour, as it came to be called, gained enormous traction, but the unknowns were nerve-racking, such as the risk of crossing the asteroid belt or the untested, essential technique of using one planet’s gravity to slingshot the spacecraft to the next. Also, the speed gain of the slingshot increases the closer the vehicle is to the planet, which for Saturn meant flying between the rings and its atmosphere—yet no one knew if this empty-looking region was a safe opening. The solution? Sending cheap trailblazers, twin robotic probes Pioneer 10 and 11, as cannon fodder.

  Pioneer 11 flew by the Saturn system during September 1979 unharmed, paving the way for the Grand
Tour. It took the first close-ups of the giant, low-resolution photographs that even today retain the haunting mystery of that first encounter. Its humble payload achieved important science, including confirmation that the two gas giants—Jupiter and Saturn, 1,300 and 800 times bigger than Earth—hold 92 percent of our Solar System’s planetary mass.

  The Grand Tour launched in 1977 in the form of science-packed twins Voyager 1 and 2. Budget constraints forced a triage between visiting Titan and Pluto. Saturn’s largest moon, bigger than Mercury, won. Pluto would need to wait until 2015 for its flyby. Voyager 1 would pass by Jupiter, Saturn, and Titan. Nine months later, Voyager 2 would cover Jupiter, Saturn, Uranus, and Neptune. Both missions were exceedingly challenging. NASA deemed the enigmatic Titan so crucial that if something were to happen to Voyager 1, Voyager 2 would alter its trajectory, sacrificing the ice giants for a Titan flyby.

  Voyager 1 encountered the Saturnian system in November 12 1980. By 6:00 AM that day it flew over Titan. The only moon in the Solar System with a thick atmosphere, its ultra-dense yellow haze prevented any visual observation of its surface. Yet the atmospheric composition, temperature, and pressure hinted at the sensational speculation that liquids could exist on its surface. By 10:00 PM it whizzed by Tethys, a moon stained with blood-red streaks and traversed by a gorge twice as deep and four times as long as Colorado’s Grand Canyon. Midnight marked the closest approach to Saturn, and instruments measured sustained winds in the upper clouds of over 1,000 miles per hour, five times stronger than the worst hurricanes on Earth.

  By 2:00 AM the next day it was Mimas’ turn, a moon scarred by an enormous crater that makes it Star Wars’ Death Star’s doppelgänger. Eight minutes later came Enceladus, made of pure water ice, making it the most reflective and one of the coldest objects in the Solar System. By 6:00 AM it was Rhea, Saturn’s second largest moon. And by 5:00 PM it was the sponge-like, potato-shaped Hyperion, the largest irregularly shaped body ever observed. Mission complete. Almost two decades and millions of man-hours gambled with no room for error in under thirty-six hours.

  The flawless performance meant a new lease of life for the spacecraft. After all, its plutonium-238 energy source still had decades of power remaining. NASA extended the mission. In 2004, six years after overtaking Pioneer 10 as the most distant man-made object from us and the Sun, Voyager 1 started crossing the termination shock, the bubble-like interface where the high-energy solar wind particles pushing outward from the Sun clash against the tide of high-energy interstellar cosmic particles pushing inward. In 2012, it officially exited the Solar System and entered interstellar space. By the mid- to late-2020s we will finally lose contact.

  On August 26 1981, Voyager 2 followed its two predecessors into the Saturn system. Two days prior it flew over the furthest large moon orbiting the gas giant, oddball walnut-shaped Iapetus, called the yin-yang of the Solar System due to its two contrasting hemispheres, one bright as snow and the other dark as freshly poured asphalt, the latter crossed by an equatorial mountain ridge more than twelve miles tall, twice as high as Everest. By 3:00 AM it flew by Saturn, analyzing the intricate structure of the rings and the preposterous contrast between their huge width, 280,000 kilometers or twenty-two Earths wide, and unbelievably narrow height, averaging just ten meters tall, smaller than the human tower world record. Half an hour later was UFO-shaped Atlas’ turn. By 4:00 AM it went past the cratered Epimetheus and Janus, locked in an endless relay race that causes them to exchange orbits every four years. It ended the Saturnian tour a week later by flying past Phoebe, a very dark moon orbiting in the opposite direction of most others, now identified as a primordial object captured by Saturn from the early Solar System. Even the small sample from Saturn’s extensive moon catalog displayed nature’s mesmerizing creativity. The probe went on to become the first and only human object ever to pay a quick visit to Uranus and Neptune.

  The Voyagers will continue traveling into forever. Messages in bottles drifting in the cosmic ocean long after the Earth has been engulfed by a Sun turned into a giant red predator. Every 225 million years they will complete an orbit around the Milky Way’s center. And if one of them ever runs into an alien civilization, it will have something inside to share: the Golden Record—a time capsule and a phonograph containing pictures and sounds from children of the Universe by then long forgotten. The last remnant of our existence, Chuck Berry’s “Johnny B. Goode” singing while knocking on eternity’s door.

  Far from waning our curiosity, the Voyagers and Pioneer 10’s flybys revealed that the giant winged planet and its entourage of moons could guard the answer to one of the most consequential enigmas of our time: Where Do We Come From?

  The Saturn system is a laboratory. Sharing the chemistry of the Sun, a bigger ball of gas would have had enough gravity for the enormous heat and pressure in its core to ignite nuclear fusion. Saturn is thus a failed star. And the largest collection of moons of any planet functions as a miniature Solar System. Studying it would help understand the origin and formation of our Solar System. Titan revealed itself as a primeval Earth frozen in time, full of rich, carbon-based compounds. Analyzing it could illuminate the development of complex chemistry and help decipher the origin of life.

  The Cassini Mission

  Planning for the next mission began in 1982. By necessity it would be the most ambitious and expensive robotic expedition ever. All three previous flybys were, well, flybys. No more first, fleeting impressions. This would be a deep dive into Saturn’s psyche, a long-term character study of the colossus and its minions.

  Titan was key mission objective, and to better understand the giant moon, landing was the only choice. In an unprecedented collaboration, NASA would build and operate the orbiter, a thirty-passenger school bus named Cassini, while the European Space Agency would be in charge of Huygens, a meter-long probe that would travel attached to Cassini, destined to parachute into Titan’s atmosphere.

  It would take almost two decades of preparation before setting off for destination Saturn. It proved to be one of the greatest voyages of discovery in the history of science.

  The sharpest eyes yet to peer at the Saturn system from up close, Cassini began uncovering new natural satellites a month before arrival. By the end of its journey the headcount of intriguing and phenomenally diverse moons in the Saturnian wonderland reached sixty-two.

  July 1 2004. Cassini soared above the rings, crossed the ring plane just outside Saturn’s F ring, turned itself, and with zero margin of error fired its engines to decelerate. At seventy minutes from Earth at light-speed, real-time remote maneuvering was impossible, making an autonomous orbit insertion mandatory. At 3:54 AM it made history by completing its capture by the giant’s gravity, which bent the probe’s path and sent it flying in the opposite direction. For the next thirteen years, Cassini completed 292 elongated orbits that toured the entire Saturn system, swinging back to the gas giant each time before accelerating and being thrown out again every couple of weeks.

  January 13 2005. It was time for one of the most awaited moments in space exploration. Huygens broke through Titan’s massive 600-kilometer atmosphere, ten times taller than Earth’s, deployed parachutes, and fell for two and a half hours into a Jules Verne fantasy world. The video feed transmitted from Huygens to Cassini, then relayed to Earth, shows extraordinarily Earth-like meteorology and geology: clouds, dunes, mountain ranges, flat plains, a surface sculpted by winds and rain with deep, serpentine canyons and rivers flowing to what appear to be mist-shrouded coastlines and islands. Cameras measured a yellowy surface illumination level similar to Earth’s sunset. It touched down and continued frenetically sending precious data before the mothership disappeared beyond the horizon. That was Huygens’ last contact with Cassini. Titan had become the most exciting location in the Solar System.

  February 16 2005. Competition was coming from the unlikeliest of candidates. Cassini’s magnetometer detected something abnormal about Enceladus, a small, icy moon 500 kilometers in diameter
, equivalent to an area twice that of Germany. Its south polar region has a balloon-shaped bulge that bends Saturn’s powerful magnetic field.

  July 15 2005. In a pivotal flyby, Cassini returned to the south pole, encountering young terrain strangely devoid of impact craters and crisscrossed by four deep, 130-kilometer-long tectonic fractures: the Tiger Stripes. It unintentionally solved the riddle while presenting one hundred others with a baffling, unexpected discovery: a cloud of water vapor and ice particles.

  July 21 2006. Titan’s breakthrough. Cassini’s radar found not just lakes but entire seas, complete with tributaries. Not of water but of liquid methane and ethane. The discovery turned Titan into the only other place in the Solar System with stable surface liquid bodies—excluding the scorching lava lakes of Jupiter’s moon Io.

  March 12 2008. An ultra-low flyby allowed Cassini to sample Enceladus’ plume, finding a brew of organic molecules: the building blocks of life as we know it.

  June 21 2011. Confirmation of a warm global salty sea, bigger than the Pacific Ocean, beneath Enceladus’ icy crust. More than one hundred individual geysers spew high-speed jets of water that collectively feed the plume, towering 1,500 kilometers above the south pole.

  April 12 2017. NASA announced a showstopper: hydrothermal activity deep down at the Enceladus seafloor. The unassuming moon instantly turned into the best candidate for alien life anywhere.

  By now Cassini was running on fumes. With the little propellant left, NASA designed a series of twenty-two daring dives between Saturn’s cloud tops and the innermost ring: the Grand Finale. A close-up of the giant’s atmosphere, and the most recognized feature in any world, the ethereal rings.

  Both Saturn and Earth have fast-flowing ‘wind rivers’ known as jet streams. Back on Earth, eastbound flights over the Atlantic Ocean usually ride them, allowing for faster travel than westbound flights. Jet streams on Earth average 180 kilometers per hour; on Saturn they can reach ten times that speed. On Earth their width is a few hundred kilometers; Saturn’s equatorial jet stream’s width is five times the size of our entire planet.