Category Dreams of Other Worlds

On a typical summer’s day in 2011, the current conditions at Space- weather. com read: “Solar Wind speed 515.9 kilometers per second, 0.3 protons per cubic centimeter.” That’s a speed of 1,125,000 mph and just one atom in the volume of a sugar cube, or a vacuum a bil­lion billion times thinner than the air we breathe. The website also predicts “X-Ray Solar Flare: 24-hr max: B4.” That’s a puny flare, thousands of times weaker than the 1859 event.9 In space weather rankings, B-class solar flares are completely “below the radar” and negligible, C-class X-ray solar flares are small and have very little impact on Earth, M-class flares cause momentary radio blackouts and can affect Earth’s Arctic and Antarctic regions, and X-class flares are major events causing planet-wide blackouts and week – long radiation storms. NOAA, the National Oceanic and Atmo­spheric Administration (more commonly known as the National Weather Service), provides detailed space weather reports updated every ten minutes. But what, one might ask, is the relevance of solar flares for our protected oasis of life on Earth, 93 million miles from the Sun?

Like a lonely sentinel stationed roughly a million miles from Earth at the Lagrangian point L1, NASA’s Solar and Heliospheric Observatory (SOHO) keeps a steady finger on the Sun’s pulse. Its game is called helioseismology, or the study of the “hum” of the sound waves reverberating throughout the Sun. Scientists use these acoustic probes to better understand its interior structure and energy production as well as possibly predict disturbances at the surface, like sunspots. SOHO has demonstrated with great clarity that solar flares—the sudden explosions of matter, electro­magnetic radiation, and high-energy particles from the Sun—can be unimaginably energetic cataclysms (plate 11). As University of Michigan Space Physics professor Mark Moldwin notes, “Flares release tremendous amounts of energy in a few minutes and can reach temperatures of 100 million K (much hotter than even the core of the Sun).”10 Space telescopes like SOHO and the new Solar Dynamics Observatory (SDO) are giving scientists a front row seat in observing the powerful dynamo of our star.

The Sun has magnetic poles. Approximately every eleven years, the direction of the poles reverses—imagine an object trillions of times bigger than a bar magnet completely reorienting its magnetic field. Such large-scale restructuring unleashes incredible magnetic forces, which lead over a few years to an exponentially greater degree of solar activity and solar storms. The tremendous ener­getic output at the most volatile stage of the process is known as the solar maximum. John Weiley’s IMAX film Solarmax (2000) has captivated audiences at planetaria and science museums with SOHO footage of the Sun’s violent storms leading up to the solar maximum of 2000 and 2001. The film’s amazing time-lapse foot­age demonstrates our Sun’s variability and the explosive energy of coronal mass ejections, plasma and magnetic fields blown off from the Sun’s corona that can cause severe magnetic storms on Earth.

The Earth’s magnetosphere largely protects us from the solar wind,11 the Sun’s outpouring of highly charged particles. More than that, this protection has been essential for the survival of life as we know it. Mars has a much weaker magnetic field and long ago lost most of its atmosphere and all of its oceans in large part due to the solar wind. However, when they reach dangerous levels, storms in space can cause power grid blackouts leaving millions without electricity, and may produce a rapid buildup of powerful electrical charges on satellites that can fry their delicate instru­ments. It has only been in the last few decades that we’ve realized the impact of space weather.

Space weather researchers highlight “evidence of the influence of solar activity on the terrestrial climate.”12 Mark Moldwin points out that in the 350-year span between AD 900 and 1250, during an extended warming period produced by increased solar activity, the North Atlantic experienced much milder temperatures. This prompted Nordic people to establish communities in Greenland and assign the region a “name that seems peculiar now since it is covered by one of the world’s largest ice sheets year round.”13 When solar activity subsequently decreased, Greenland froze over and settlers there either migrated or died. Later, during what is often called the Little Ice Age, lasting roughly between 1550 and 1750, historians report “winters were so cold. . . the principal riv­ers in mid-latitude Europe froze over.”14 This has been attributed to a solar minimum and apparently an extended period in which there were few sunspots.

The Earth naturally has gone through cycles of ice ages, but as Moldwin explains, the most recent, the Quaternary, extended from 2.5 million years ago to about 10,000 years ago, when large reaches of ice receded. The problem we’re currently facing is global warming, where temperatures consistent for the last 10,000 years are now on the rise. Moldwin writes, “Model predictions indicate that Earth’s climate will be drastically different than it is today in less than 100 years because of the burning of hydrocarbon fuel for transportation and energy. That is very quick compared to the nor­mal timescale of climate change.”15 Added to this is the fact that solar storms can seriously damage the Earth’s ozone layer, which protects all life on Earth from damaging ultraviolet rays and could, in turn, further contribute to warming Earth’s atmosphere.

NASA created its “Living with a Star” program in 2001 to gather better data for understanding the effects of the Sun on the Earth.16 If we ever move beyond our planet and engage in routine space exploration, we must leave the protective “bubble” provided by the Earth’s magnetic field and atmosphere. Our spaceships and astronauts will have to deal with the Sun and its stormy weather directly. A small armada of spacecraft has been involved in this ef­fort, but the most notable is a very sturdy device that’s still going strong seventeen years after its launch.

Space is mostly empty, but a thin gruel of gas and dust that occupies regions between stars dims and reddens light.1 Thousand-trillion- mile wide clouds containing gas and microscopic dust grains ab­sorb and attenuate visible light and reradiate it at infrared wave­lengths. NASA’s Spitzer Space Telescope has the remarkable ability to see through interstellar dust and has allowed us to look into the vast clouds in which stars are born, like those of the Orion Nebula, our nearest star-forming region. Spitzer can also peer into the dark, dust strewn plane of our Milky Way galaxy that previ­ously had been nearly impossible to penetrate. Anything that ra­diates heat, such as living bodies, and any cool object in space, such as planets or moons or even tiny silicate (rocky) and carbon (sooty) grains 1/10,000 to 1/100 of a millimeter across, emits in­frared radiation. Only an infrared telescope can image objects that glow in light waves too long for the human eye to see. The Spitzer Space Telescope can detect such light billions of light-years from Earth and has revealed this cool and invisible universe with un­precedented clarity.

With more than 850 exoplanets known as of early 2013, and another 2,700 candidate planets identified by the Kepler telescope, astronomers estimate that there are at least 50 billion exoplanets in the Milky Way galaxy. Scientists calculate that 500 million of those planets orbit in the habitable zone, the distance from their star that could allow for life.2 NASA’s Spitzer Space Telescope is helping to

detect and characterize these extrasolar worlds. In December 2010, Spitzer discovered the first carbon-rich exoplanet, named WASP- 12b, the geology of which may be comprised largely of diamond and graphite.3 Whereas rocks on Earth generally consist of silicon and oxygen in the form of quartz and feldspar, Spitzer’s observa­tions suggest that WASP-12b, about 1,200 light-years from here, has nothing like terrestrial geology. Astronomer Marc Kuchner of NASA Goddard Space Flight Center, who has helped theorize carbon-rich planets, explains that increased carbon in a planet’s composition can entirely alter its geology: “If something like this had happened on Earth, your expensive engagement ring would be made of glass, which would be rare, and the mountains would all be made of diamonds.”4 Spitzer has been instrumental in analyzing the geological makeup of exoplanets, and what astronomers are finding exceeds their wildest expectations.

At the other extreme from dim worlds in the nearby universe, Spitzer has discovered massive galaxies billions of light-years away that are forging stars at a prodigious rate. An infrared-bright, star­forming galaxy might be making thousands of stars each year compared to a couple for the Milky Way. These “starburst” galax­ies are infrared beacons from the early construction phase of the universe, during which many large galaxies were being assembled from smaller galaxy “pieces” for the first time.5 Deep within the dust-obscured hearts of distant galaxies, new worlds were being forged at a fantastic rate. A single, modest-sized telescope in space has seen directly into the center of these galaxies and provided insights on the full range of their creation stories.

As we saw in the last chapter, Mars seems dead to the orbiters that daily send back images of the surface. The atmosphere is tenuous, ultraviolet radiation and cosmic rays scorch the soil, and it rarely gets above freezing even on the balmiest summer day.15 It’s un­likely any form of life could exist on the surface now, but Mars has not always been so inhospitable. NASA’s strategy in searching for life in the Solar System is to “follow the water,” and even if there’s no surface water now, there was in the past. Each of the Mars Ex­ploration Rovers, Spirit and Opportunity, was designed for just a ninety-day mission. In the end, they have vastly exceeded expecta­tions with their indomitable traverses of the forbidding Martian terrain. Think of them as twin robotic field geologists whose pri­mary goal is to search for the signposts of water.16 The record of past water can be found in the rocks, minerals, and landforms on Mars, particularly those that could only have formed in the pres­ence of water.

Spirit and Opportunity were not designed to detect current or past life in the Martian soil,17 but they can do the detective work needed to say whether there have been stable bodies of water that could have supported life in the past. Surface rocks reveal evidence of previous water in the way that they formed, by processes like precipitation, evaporation, and sedimentation. They can also hold clues for the possibility that water currently exists under the sur­face. The rovers have helped scientists diagnose the history of the Martian climate, which is now thought to have been warmer and wetter 2-3 billion years ago. The twin robots are also trying to parse the different contributions of wind, water, plate tectonics, volcanism, and cratering to the sculpting of the surface. Spirit and Opportunity provide “ground truth” data for calibrating the or – biters that continue to do remote geology and scout for future landing sites. A final goal is to prepare the stage for future as­tronauts by understanding the unique challenges of the Martian environment.

Chesley Bonestell’s lifelike paintings of Saturn as seen from the surface of Titan and other moons, published in 1944 in LIFE magazine, sparked the public imagination regarding the kind of geographies we would someday find in the outer Solar System. In characterizing the large gas planets and their moons, Voyager con­firmed what astronomers had long suspected: the Earth to some degree serves as an analog for meteorological and geological pro­cesses on other worlds. Serge Brunier explains, “Fogs, clouds, gla­ciation, the cycle of the seasons, aerial erosion, and volcanism are universal phenomena.”26 But the geological processes occurring on worlds billions of miles from the Sun both surprised and mes­merized scientists and space enthusiasts across the globe. Close-up views of Jupiter’s moons indicated internal heating as they flex in the tides of their host planet’s gravity. A probable ocean of water captured under the fractured and icy surface of Europa, and Ti­tan’s seas of liquid methane, both suggested strange and captivat­ing geographies.

Planet encounters garnered global attention and were keenly covered by the press. When Voyager 1 arrived at Saturn in Novem­ber 1980, Henry Dethloff and Ronald Schorn report that approxi­mately 100 million people tuned in to live television broadcasts from NASA’s Jet Propulsion Laboratory while roughly five hundred reporters from across the globe provided news coverage “unprec­edented in the history of unmanned space exploration.”27 It’s no wonder public interest in the mission was so intense. Voyager liter­ally beamed into our living rooms footage of worlds being charted for the first time. Of Voyager 1’s encounter with the second larg­est planet in our Solar System, former JPL Director Bruce Murray writes: “Both Time and Newsweek ran Saturn cover stories. Live

programming flowed daily from Pasadena to a network of view­ers in countries ranging from Canada to Finland and, especially, Japan. Colorful images of Saturn surrounded by its magnificent rings rapidly became pop art cultural symbols.” Saturn’s weather turned out to be wilder than Jupiter’s. A layer 1,200 miles thick has winds of over 1,000 mph. Murray recalls that President Jimmy Carter, curious about wind speeds and whether auroras had been detected on Saturn, phoned to say: “The Saturn pictures are fan­tastic. I watched two hours yesterday as well. Didn’t expect to have so much time available.” In the summer of 1989, when Voyager 2 arrived at Neptune and its moon Titan, black and white still im­ages were broadcast live as they streamed from the spacecraft, and NASA, PBS, and CNN arranged for live reports at regular intervals throughout the encounter. Voyager’s televised encounters allowed scientists and general audiences opportunity to ramble “through a cosmic Louvre,” writes Murray. “For the millions viewing PBS’s ‘Jupiter Watch’ telecasts, ABC’s ‘Nightline’ programs, or Carl Sa­gan’s ‘Cosmos’ series or watching the images appearing on screens in Japan, England, Mexico, and South America, Voyager revealed a treasure trove of abstract art.”28

Carl Sagan was a member of Voyager’s imaging science team and he incorporated into his PBS TV program Cosmos (1980) ani­mations of planetary flybys and computer-generated graphics pro­duced at JPL by the Voyager team.29 Through the PBS series, his book of the same title, and late night talks with Johnny Carson, Sagan worked to capture and generate widespread public interest in planetary science and the Voyager mission. A celebrated senior astronomer at Cornell University, Sagan dedicated his life to popu­larizing the latest findings in astronomy and planetary science, at a time when most astronomers were unwilling to risk their schol­arly reputations to do so. He fed a fascinated public exactly what they hoped for and wanted. Having researched the atmosphere of Venus as an example of runaway greenhouse effects, Sagan championed NASA’s projects and delighted in articulating in de­scriptive imagery astronomical and planetary phenomena. It was Sagan who suggested that Voyager, once beyond the orbit of Nep­tune and receding from the ecliptic plane, should capture a pho­tograph of Earth as it really appears in the scale of the Solar Sys­tem—a seemingly unimpressive “pale blue dot” as he evocatively named it.

Before Cassini arrived at Saturn, astronomers had paid little atten­tion to Enceladus, a moon one-tenth the size of Titan. The Voyag­ers had shown in the 1970s that Enceladus was like an icy billiard ball, reflecting almost 100 percent of the Sun’s light. Its surface gave indications of activity since some parts were old and heavily cratered while others seemed to have been altered by volcanism in the last hundred million years. But nothing in earlier data prepared scientists for what Cassini would reveal.

In 2005, plumes were seen rising from the fractured, icy surface (figure 5.5). It took several years and numerous observations by Cassini’s instruments to build up a picture of what was going on, but this is what we know. Enceladus emits geysers of tiny ice par­ticles from a number of hot spots on its surface, near the southern polar region. The plumes are ejected at over 1,000 mph, greater than the escape velocity. They rise thousands of miles above the surface and form Saturn’s E ring.42 The geysers arise from geologi­cal features called “tiger stripes” that are 100-200°F warmer than

other areas of the moon. Geologists think there’s spreading and tectonic activity in the tiger stripes, similar to what happens near deep-sea ocean ridges on Earth. Tidal heating must play a role, but the cause of the active geology on Enceladus is still a mystery, since the neighboring and similarly sized moon Mimas is inactive. Cas­sini has swooped through the plumes on several occasions, three times approaching the moon within 30 miles, “tasting” the mate­rial with its instruments to determine the chemical composition. The plumes are made of tiny ice particles and vapor that includes methane, ethane, propane, acetylene, and other organic molecules. The chemical composition may be like a comet. Most excitingly, the plumes contain sodium chloride—common salt. That’s the best indication so far that Enceladus has a subsurface ocean that oc­casionally erupts through the surface.

Much of this information was gathered in a series of swooping flybys, the closest of which zoomed within 15 miles of the surface. The imaging team calls these maneuvers “skeet shoots.” The space­craft is moving so fast and is so close to the moon that the camera can’t track or lock onto any particular geological feature. Some images resolve features as small as 10 meters across, about the size of a living room. In late November 2009, Cassini made its eighth flyby of the tiny moon, the last before Enceladus entered the shad­ows of the long, cold Saturnian winter. With no new mission slated to return to the outer Solar System for at least fifteen years, it will be a while before we see images like this again. Meanwhile, the presence of liquids on Titan and inside Enceladus naturally leads to speculations about biology. Our dreams turn to the possibility of creatures floating in the dark and frigid depths of lunar seas far from their sheltering stars.

On December 2, 1995, the Solar and Heliospheric Observatory (SOHO) spacecraft was launched onboard an Atlas rocket from Cape Canaveral in Florida. It’s the size of a minivan, or, with its solar panels extended, about the size a school bus, and it weighs roughly two tons. SOHO was conceived by the European Space Agency; fourteen countries and more than three hundred engineers were involved in its design and construction. NASA was respon­sible for the launch and ground operations. It’s a testament to the power of collaboration that so many nationalities can work to­gether to produce a state-of-the-art scientific experiment.

SOHO is like a Swiss army knife, reminiscent of Cassini in its size and complexity. Its available space is crammed with twelve instruments that can measure everything from magnetic fields to X-rays. Nine instruments are led by European scientists and three are led by scientists from the United States, but all of them have teams that are a patchwork quilt of nationalities. Unnoticed by the fractious world of politics and tribalism, science is one field of en­deavor where national distinctions and borders are almost mean­ingless. Some of the instruments have intimidating names, like the “Comprehensive Suprathermal and Energetic Particle Analyzer” built by the University of Kiel in Germany, but generally they all measure the location, intensity, and spectrum of either high-energy X-ray and ultraviolet radiation or cosmic rays. Multinational har­mony does not, however, extend to gender parity. Space astronomy is still male-dominated; all twelve instrument principle investiga­tors and 80 percent of the science team members are men.17

SOHO moves around the Sun in step with the Earth, by slowly rotating around a point in space called the first Lagrangian point (L1), where the sum of the Sun and the Earth’s gravity combine to keep the satellite locked onto the Sun-Earth line.18 This position is about a million miles away from the Earth in the direction of the Sun, about four times the distance to the Moon. SOHO’s eyrie gives it a ringside seat for watching solar activity. Other space mis­sions are using or plan to use L1, but it’s perfect for solar observa­tions since a spacecraft in this orbit is never shadowed by the Earth or the Moon.

SOHO has been beaming data to the Earth from twelve scien­tific instruments at a gigabyte, or two CD’s worth, per day. Analy­sis of this data has yielded some exciting insights into the Sun, including the first images of a star’s convection zone, where energy is carried from the fusion core to regions near the surface, and the structure of sunspots just below the photosphere. SOHO has also provided the best measurements to date of the temperature, rota­tion, and gas flow patterns within the Sun, and it has revealed new types of solar activity, such as waves in the corona and tornadoes on the surface. As of late 2012, SOHO data had been used to dis­cover over 2,350 comets.19 The spacecraft had a nominal lifetime of two years. In 1997, it was extended for five years due to its great success. In 2002, it got another five-year extension, and in 2009 it got a third extension, until the end of 2012. SOHO is now well into its second solar cycle of observations. However, it was not always smooth sailing.

We inhabit a physical universe filled with electromagnetic radia­tion spanning a factor of trillions in wavelength. The human eye sees only a sliver of this radiation, designated as visible light. It’s as if there was a full piano keyboard in front of us with eighty-eight keys and we were restricted to making music with two adjacent keys or notes. Space telescopes like Spitzer and the Chandra X – ray Observatory, covered in the next chapter, have opened up the palette of sensation and given us an octave or more with which to view the universe. Infrared astronomy, in particular, has been instrumental in revealing how stars and their planetary systems form. Spitzer can see through the vast clouds of dust, within which myriad stars are being born, and can penetrate the granular torus or dense disk that typically surround newborn stars. This capabil­ity has literally opened people’s eyes to the worlds that lie beyond the red end of the rainbow.

Isaac Newton first identified the colors of the visible spectrum by observing sunlight passed through a glass prism. William Her – schel later investigated temperatures associated with each color of visible light. Having in 1781 discovered Uranus, the first new planet since antiquity, Herschel was already the greatest astrono­mer of his age when he began experimenting with light. He noticed that heat passed through various colored filters used to observe the Sun and carried out experiments to understand this phenomenon. Using a thermometer with a soot-blackened bulb to better absorb heat, Herschel measured the temperature of each color band of vis­ible light and noticed that the temperature increased from the vio­let to the red end of the visible spectrum.6 Surprised to record the highest temperatures beyond the edge of the red band, Herschel realized that electromagnetic radiation existed in wavelengths we can’t see. He had detected infrared light. Such early discoveries regarding the electromagnetic spectrum paved the way for remark­able new possibilities in studying the universe.

Light is conventionally subdivided by wavelength into radio, microwave, infrared, visible, ultraviolet, X-ray, and gamma ray, with radio designating cool, long wavelengths and gamma rays representing the highest energy, short wavelengths. These subdi­visions are merely convenient demarcations for differences along a continuum of electromagnetic radiation. While most forms of radiation can’t reach the ground from sources in space (figure 9.1), all forms of electromagnetic radiation, from radio to gamma rays, travel at the same speed as light in a vacuum, approximately 300,000 kilometers per second or 186,000 miles per second. We’re intimately familiar with most of these bands of radiation. Radio waves transmit music and news on your favorite radio station. Microwaves make possible communication technologies including cell phones and, of course, in microwave ovens. Ultraviolet radia­tion can quickly give you a suntan or sunburn and is the means by

which our bodies produce Vitamin D. We became familiar with UV light from the 1970s black lights. X-rays have been invaluable in medical and dental practice as well as in fluoroscopy, which offers real-time views through living tissue, while high-energy lasers are used in brain and eye surgery and other delicate medical proce­dures. Radiation at infrared wavelengths also has powerful thera­peutic effects. Low-level, “cold laser” therapy contributes to the healing of wounds as noted in a report cited by the National Cen­ter for Biotechnology Information.7 A near infrared light-emitting diode developed by NASA has been used to heal and reduce pain for chemotherapy patients who subsequently suffer from mouth lesions.8 In the past fifty years, we’ve harnessed this invisible radia­tion to vastly improve our lives.

Spirit and Opportunity are squat and sturdy, as large as golf carts and almost as tall as an adult (plate 3). Each weighs 400 pounds.18 They have six wheels, each with its own, independent motor. Four – wheel steering allows them to make tight turns and swerve or turn on a dime. The design is based on the “rocker-bogie” system of the previous Sojourner rover.19 The wheels can swivel in pairs and pivot vertically to maintain overall balance. The saddest thing that could happen to a very expensive rover millions of miles from home would be for it to tip over onto its side or back, wheels spin­ning uselessly. So Spirit and Opportunity have a suspension system that balances the load any time a wheel goes up or down. As a result, the bodies of the rovers experience half the range of motion of the wheels and legs. The rovers can tilt up to 45 degrees without overturning, but software is designed to sound the alarm any time the tilt exceeds 30 degrees. The wheels have cleats for gripping in soft sand and scrambling over rocks.

In case you had a mental image of a NASA engineer, cap turned sideways, slamming a joystick from left to right as the rover ca­reens over the Martian dunes, the truth is a bit more sedate. The rovers have a top speed over smooth ground of 2 inches per sec­ond, or 1/10 of a mile per hour. But even at that speed, there’s no danger of recklessness; hazard avoidance software is used that makes each rover stop and evaluate its progress every couple of seconds, reducing the true speed to a glacial 1/50 mph. On Earth, the rover might get overtaken by a snail.

The body of the rovers is the warm electronics box, a tough outer layer designed to protect the computer, electronics, and batteries—the rover’s brains and heart. These vital organs must be buffered from the worst extremes of the Martian climate. Tem­peratures at the landing sites can plunge from a daytime high of 70°F to a nighttime low of -150°F, a range many times larger than we’re accustomed to on Earth. Engineers use gold paint, heaters, and insulating aerogel to keep the rovers in a comfort zone. Within the warm electronic box, the “brain” of each rover is a computer that receives data from the scientific instruments and relays it to one of the Mars orbiters and then on to Earth. Spirit and Oppor­tunity are exquisite machines, but they’re far from state of the art in terms of processing power and data transmission rate. Moore’s law—the near doubling of computational power every eighteen months—marches on, but the hardware on the rovers had to be tested for the severe conditions of space and “frozen” long before launch. So each rover’s brain has only 128 Mb of RAM, and the data rate to the orbiters is 128 kb per second. That’s the equiva­lent of a very low-end netbook and only twice as fast as a dial-up modem. If you have an iPhone, it easily eclipses the computational capabilities of both rovers.

The beating heart of the rovers is their solar panels. Mars re­ceives half the intensity of sunlight that the Earth does, and it’s a real challenge to gather enough energy to power the rover and its suit of instruments. Each rover can function on 140 Watts, the equivalent of a standard light bulb. The deck of each rover is tiled with solar panels which charge batteries within the warm electronic box. As the Martian winter approaches, there’s insuf­ficient power for driving, so each rover navigates to a north-facing slope and hunkers down for the months in which the tempera­ture remains below freezing. This imperative has always been greater for Spirit, which is much farther from the equator than Opportunity.

Of the stunning images Voyager sent back, perhaps none have more profoundly shaped our understanding of humankind’s place in space than Voyager 1’s photo of Earth from the icy reaches of the outer Solar System. The “Pale Blue Dot” image represents one of the most significant of the mission and of our time. In Febru­ary 1990, while 3.7 billion miles from Earth, Voyager 1 snapped sixty photographs looking toward the Sun, and over the next three months transmitted the images to Earth. Among the last six frames of the photo shoot, only one included humankind’s most distant view of Earth. When Sagan suggested that Voyager’s imaging team attempt the photographs, NASA administrators apparently were reluctant to authorize it, as programming the commands to take additional images was labor intensive and it was not clear whether the data would be scientifically useful. Candice Hansen, who helped design Voyager’s imaging observations, and several oth­ers joined Sagan in arguing for the photographs. Hansen recalls how intently the imaging science team wanted to obtain what was later called the Family Portrait: “We were really after the picture of the Earth, so we had to look for the point in the Earth’s orbit which would have it as far away as possible from the Sun. It turned out that we could also get Neptune, Uranus, Saturn, Jupiter, and Venus.” Hansen, like Sagan, realized that an image of Earth viewed from billions of miles away would intrinsically “strike a chord. . . that might affect people’s view of the world.”30 They couldn’t have been more prescient.

By sheer chance, the Earth appears in the photo as though caught in the band of a rainbow. This artifact in the image is caused by sunlight reflecting off the spacecraft (figure 4.3). Sagan noted that it only accentuated how diminutive our world is in the empty wastes of outer space. Jurrie Van Der Woude, public infor-

mation officer for the mission, explained the difficulties in actually acquiring Voyager’s final six photographs, including the singular image of Earth that so powerfully and visually characterized our minute place in space:

They were stored onboard Voyager on the tape recorder, for the simple reason that the Deep Space Network—those big antennas in Australia, Madrid, and Goldstone, California—were too busy with Ma­gellan and Galileo to listen to poor old Voyager. At the end of March, we played that sequence of photographs back, and the last series of photographs, five or six, were being received by the Madrid antenna when it rained. That blocked out the data, so in April we had to give it another shot. This time the antenna in use was the one at Goldstone, which turned out to have a hardware problem. As a result we still did not get those six photographs, so we had to do it again in May, when we finally got them.31

Wyn Wachhorst writes, “To stand on the moons of Saturn and see the Earth in perspective is to act out the unique identity of our species.”32 Wachhorst quite accurately points out that viewing Earth from the outer planets had radically altered our collective human consciousness. The Apollo missions afforded us the first opportunity to see the Earth from 240 million miles away. Apollo 8’s photo of the gibbous Earth emerging from the limb of our desic­cated and cratered Moon, Earthrise, along with Apollo 17’s Whole Earth photo are among the defining images of the manned lunar program and of the twentieth century. Apollo 8 astronaut James Lovell, commenting on the view of Earth as the astronauts orbited the Moon in December 1968, noted: “The [E]arth from here is a grand oasis in the big vastness of space.”33 Voyager, conversely, had captured a chance glimpse of the dot of Earth forging into the empty abyss on its course around the Sun. In 4.5 billion years, our Solar System has never traversed the same wastes of space—nor will it ever. It is a staggering reorientation made visceral through the photo of the pale blue dot. With that single image, Voyager brought into focus the fractional blue world on which our lives, our narratives, and our art have mattered.

In Alien Ocean: Anthropological Voyages in Microbial Seas, Stefan Helmreich argues that the discovery of life deep in Earth’s oceans provoked increased speculation about the possibility of life in ex­traterrestrial seas. Prolific communities of tubeworms, krill, and other hypothermophiles were discovered near deep-sea hydrother­mal vents in 1977 in the Pacific Ocean.43 These organisms live in complete darkness—no sunlight can penetrate to these depths. Sci­entists speculate whether life in primordial times thrived in the sulfur-rich heat plumes that spew nutrients from the ocean floor. Besides the fact that we believe all life on Earth originated in the sea, we have long imagined, notes Helmreich, that extant primeval life-forms might somehow survive in the deep, even today. Life’s origins may best be represented by extremophiles currently living in extreme environments. He writes, “Some marine microbiolo­gists maintain that vent hyperthermophiles are the most conserved life forms on the planet, direct lines back to the origin of life.”44 What we are learning about extremophiles or methanotrophes— bacteria that metabolize methane—may indicate something of the possibilities for life on other worlds. “Astrobiologists treat unusual environments on Earth, such as methane seeps and hydrothermal vents, as models for extraterrestrial ecologies,” writes Helmreich.45 Cassini has revealed that several of Saturn’s moons have liquid or frozen oceans and briny geysers. Enceladus, with its outgassing plumes of ice water and salt, and Titan, are of particular inter – est.46 As the planetary body in the Solar System most similar to

Earth in atmospheric composition, Titan could reveal how life on Earth emerged, suggests astrobiologist Chris McKay.47 Since Titan and Enceladus are likely heated internally by Saturn’s gravitational squeezing, astrobiologists imagine that extremophiles might hud­dle near hydrothermal vents on the floors of their arctic seas. On Earth, Lake Vida in the Antarctic has been capped under a 50-foot thick ice sheet for 2,800 years and yet researchers found ancient microbial life thriving there.48 Helmreich comments, “For astro – biologists, life, extremophilic or no, will exist in a liquid medium. It is for this reason that extraterrestrial seas—alien oceans—are such objects of fascination.”49 In these discoveries alone, the im­plications of the Cassini mission are as deeply cultural as they are scientific.