Category Dreams of Other Worlds

From time immemorial we have projected our stories, myths, and legends onto the night sky. Seeing patterns among the stars was a serious preoccupation from primordial time. Our shared narra­tives about the constellations, across cultures and millennia, served as a survival mechanism not to be underestimated or discounted as simple tales of mythological figures. Biocultural theorist Brian Boyd claims that human attention to pattern emerged as an evo­lutionary adaptation. Boyd and other scholars contend that arts relying on patterns such as storytelling, song, and cave painting emerged via natural selection and allowed individuals and clans to better collaborate and share information that enhanced survival.4

Recent analyses of prehistoric paintings and markings in caves in France have revealed a series of twenty-six symbols that may reflect humankind’s earliest attempts at pictographic writing, traditionally thought to begin about 3,000 BC. Anthropologists Genevieve von Petzinger and April Nowell collated a database of cave signs from 146 sites in France dating from 35,000 to 10,000 years ago. “What emerged was startling: 26 signs, all drawn in the same style, appeared again and again at numerous sites.”5 The symbols range from straight lines, to circles, spirals, ovals, dots, Xs, wavy lines, and various hand symbols among others. Similar symbols have been found at Paleolithic sites around the world.

Certain symbols studied in France frequently appear in deliberate groupings, such as the occurrence of dots with a particular hand symbol, which may indicate the beginnings of a system of writing. As Nowell speculates, “We are perhaps seeing the first glimpses of a rudimentary language system.”6

The celebrated Lascaux cave paintings not only incorporate these symbols, but may also include representations of the Pleia­des and Hyades star clusters and an ice age panorama of the night sky. Clive Ruggles and Michel Cotte, who in 2010 headed the In­ternational Astronomical Union’s Working Group on Astronomy and World Heritage, reported to UNESCO that some archaeoas – tronomers contend a series of dots above the aurochs in the Hall of the Bulls represents the Pleiades star cluster and that one of the auroch’s eyes and adjacent dots may depict the star Aldebaran and the Hyades cluster.7 The French government’s website on Las – caux’s cave art notes that in all of the renderings, the horses were painted first, then the aurochs, and then the stags. These animals apparently correspond to the seasons of spring, summer, and au­tumn, respectively, providing “a metaphoric evocation that, in this setting, links biological and cosmic time.”8 Even more fascinating is Chantal Jeques-Wolkiewiez’s assertion that two panels of these cave images may depict the night sky as perceived by Magdalen – ian people from the top of Lascaux hill during a summer solstice roughly 17,000 years ago. Besides comparing the cave paintings to computer models of the night sky in the last ice age, she also found that light during sunset at the summer solstice stills enters the cave to illuminate some of the paintings.9

While it may be very difficult to determine whether the dots in the Lascaux paintings are indeed asterisms, the markings ice age peoples at Lascaux left next to their remarkable paintings entic­ingly suggest they were meaningful forms of communication. Ex­trapolating from such biocultural and archaeological research, it seems likely that our attention to patterns seen in constellations in the night sky extends back to our earliest days.

The names of stars and designation of constellations as we know them in Western culture are so ancient that their origins remain elusive.10 Long before the earliest written records, humankind told narratives about the stars and clustered them into constellations, which served as mnemonics for travel and navigation and as a re­pository of knowledge about the seasons, but also of legends and myth. Only in the last 3,600 years do we find unequivocal evidence of tracking the stars. Chinese rulers employed court astronomers to record information regarding stellar motions, transients, and as­tronomical events such as supernovae. But even older than ancient Chinese records is the Nebra sky disc. Discovered near the town of Nebra in Germany, the Nebra sky disc is believed by archaeo – astronomers to be a Bronze Age durable sky map dating back to 1600 BC.

The disc was uncovered in 1999 by treasure hunters who hit upon an ancient burial site in a circular earthwork enclosure at the top of Mettelberg Hill. The disc, 30 centimeters or 11.8 inches in diameter, was found with two bronze swords among other items. The sky disc is made of bronze with gold overlays of the Sun, the Moon in phase, and multiple stars. Gold bands on its sides indicate the east and west horizons and mark an angle of 82.5 degrees. At Nebra, sunset at the winter and summer solstices is visible on the horizon 82.5 degrees apart. As the angular separa­tion of those setting points varies at differing latitudes, some ar – chaeoastronomers are convinced that the disc was constructed in the Nebra region and is the oldest extant sky map in the world. A cluster of seven gold dots on the disc are thought to be the earli­est known representation of the Pleiades star cluster, used in the ancient past for identifying seasons of planting and harvest (figure 8.1). Investigation of its metal composition traces the disc to a Bronze Age mine in the Alps. The site where the disc was found is only 15 miles from Goseck, Germany, the location of a Neolithic ceremonial woodhenge dating to 7,000 years ago that researchers say clearly marks the position of sunrise on the horizon on the summer and winter solstices. Archaeologist Harald Meller, who posed as a buyer and worked with Swiss police in a sting opera­tion to capture underground traders attempting to sell the sky disc, points out that it predates “the beginning of Greek astronomy by a thousand years.”11

The ancient Greek writers Homer and Hesiod knew the names of recognizable stars and star clusters like the Pleiades and Hyades, and of constellations such as Ursa Major, the Bear. The Iliad and The Odyssey, attributed to the poet known as Homer, remain the

oldest extant Greek texts we have. Homer’s tales were rooted in an oral tradition that extends back centuries prior to their being recorded. In The Iliad, traditionally dated to approximately 700 BC, some of the constellations we know today appear on the shield that Hephaistos forged for Achilles:

He made the Earth upon it, and the sky, and the sea’s water, and the tireless Sun, and the Moon waxing into her fullness, and on it all the constellations that festoon the heavens,

The Pleiades and the Hyades and the strength of Orion and the Bear.12

James Evans also notes Homer’s description of Odysseus orient­ing his ships by keeping the constellation Ursa Major, which turns about the celestial north pole, left of his vessels as he sails East.13

One significant reason early agrarian societies marked the stars in the night sky was to develop an agricultural calendar, initially important for planting and harvesting. Evans points out that a few generations after Homer, Hesiod wrote Works and Days, the open­ing lines of which directly associate the rising and setting of star groups with agriculture:

When the Pleiades, daughters of Atlas are rising,

Begin the harvest, the plowing when they set.14

Evans explains that winter wheat was the only wheat planted in Greek antiquity, so that when the Pleiades were setting in the west in late fall it was time to plow the ground and plant the wheat.

Nick Kanas points out that ancient Greek astronomers supple­mented their knowledge of the night sky with what they could glean from the Egyptians and Babylonians: “From the Egyptians, they learned about the length of the year, its break-up into a 12-month calendar, the division of day and night into 12 hours each. . . . From the Mesopotamians, they learned a sophisticated system of constellations[,] especially involving the zodiac along the ecliptic.”15 Babylonian temple scribes conducted serious as­tronomical observation and carefully preserved their records on cuneiform tablets. Many of these astronomical records have been recovered, some of which date to the seventh century BC. A few of the most well known of these tablets are titled MUL. APIN, mean­ing “Plow Star,” the title of which apparently refers to the stars of the Triangulum constellation and the star Gamma Androme – dae, not Ursa Major, also known as the Plough, Big Dipper, or the Bear. Evans observes that the MUL. APIN tablets, copies of much older texts, begin with a list of dozens of stars and provide a star calendar indicating the rising and setting of stars at particu­lar times of the year. Also included in the tablets, which are more accurate than Hesiod’s agricultural calendar, are observations of various constellations as well as the planets Mercury, Venus, Mars, Saturn and Jupiter, the planet associated with the primary god of Babylon.

Ancient Greek astronomers thought of the stars as fixed or un­movable. However, the Greek astronomer Hipparchus, after whom ESA’s Hipparcos mission is named, was an accurate observer who “suspected that one of the stars may have moved, and. . . wished to bequeath to his successors data against which any future sus­pected movements might be tested.”16 Hipparchus was interested in what today is called astrometry, or the science of measuring the position and motions of stars and other astronomical objects. He produced a star catalog now lost or destroyed. According to Floor van Leeuwen: “The oldest catalog of stellar positions we know of is the compilation made around 129 BC by Hipparchus, a catalog that is still being investigated. Its only surviving copy appears to be a map of the sky on a late Roman statue, and is known as the Farnese Atlas.”17

For thousands of years, all we’ve known of Hipparchus’s star guide were descriptions by Ptolemy. But astronomer Bradley Schaefer asserts that, indeed, the Farnese Atlas (figure 8.2), a statue of the Greek figure Atlas kneeling while holding on his shoulders a globe of constellations, represents the stars and constellations known to the ancient Greeks. He contends that the statue “is the oldest surviving depiction of the set of the original Western con­stellations, and as such can be a valuable resource for studying their early development.”18 Schaefer realized after a detailed study of the globe that the constellations depicted match the night sky in the era and from the location where Hipparchus lived in 129 BC. As evidence in favor of this possibility, Schaefer writes: “First, the constellation symbols and relations are identical with those of Hipparchus and are greatly different from all other known ancient sources. Second, the date of the original observations is 125 ± 55 BC, a range that includes the date of Hipparchus’s star cata­logue (c. 129 BC) but excludes the dates of other known plausible sources.” Schaefer concludes that “the ultimate source of the posi­tion information [of the constellations on the globe] used by the original Greek sculptor was Hipparchus’s data.”19

Hipparchus was the first to identify the Earth’s precession, pro­duced by the gravity of the Sun and Moon on the Earth’s equato­rial bulge. The “precession of the equinoxes” refers to the gravi­tationally induced, gradual shift in the Earth’s axis of rotation, so

that the equinoxes occur earlier each sidereal year over the course of 25,765 years, when this cycle of precession begins again. Preces­sion is a changing view of the stars caused by a subtle variation in the Earth’s orbital orientation relative to the Sun; it’s not related to the kind of stellar movement that ESA’s Hipparcos mission has charted.20 As Michael Perryman explains, the Hipparcos mission is based on the concept of parallax: “The key to measuring stellar distances is actually based on the classical surveying technique of triangulation. It simply makes use of the fact, known since the time of Copernicus, that the Earth moves around the Sun, taking one year to complete its orbit. This yearly motion provides slightly dif­ferent views of space as we speed around the Sun.” We experience the same effect in observing an object by first closing one eye and then the other. Perryman points out that “this stereo vision gives us depth perception and allows us to estimate distances, at least to nearby objects. . . . Astronomers use the same stereo technique, but with views of the celestial sky separated by hundreds of millions of kilometers as the Earth moves around the Sun. In this way, Na­ture has generously and serendipitously granted us the possibility of measuring distances stretching across the vast expanse of our Galaxy.”21

Viking 1 was launched from Cape Canaveral on August 20, 1975. Its twin was launched on September 9, 1975, and Viking 2 reached Mars on August 7, 1976, a few weeks after the first triumphant landing. The second lander reached a site several thousand miles away at Utopia Planitia on September 3, 1976, after suffering its own small mishaps. The downward looking radar was probably confused by a rock or reflective surface, so the thrusters fired too long, cracking the soil and throwing up dust. It stopped with one leg resting on a rock, tilting the lander by eight degrees. Otherwise, it was unharmed. The hardware was designed to last for ninety days but proved to be very durable.36 Viking 1’s orbiter lasted nearly two years and Viking 2’s orbiter lasted just over four years. Meanwhile, on the surface, the Viking 2 lander ceased operating when its battery failed after three and a half years, while the in­domitable Viking 1 lander was going strong after more than six years, when simple human error during a software update made the antenna retract and communication with the Earth was lost.37

Public attention focused on the landers, with their life detection experiments and “you are there” images, but the orbiters were also very important in shaping a modern view of Mars. The orbiters carried the landers to Mars, scouted for landing sites, and relayed lander data back to Earth. Each equipped with optical and infrared imagers, they mapped 97 percent of the surface and sent back over 46,000 images. They could see features 150 to 300 meters across anywhere on the planet, and in selected areas they could resolve features the size of a small house.38 Whereas Mariner had only seen old, cratered terrain, the Vikings saw a rich and varied topogra­phy and geology. There were immense volcanoes, corrugated lava plains, deep canyons, and wind-carved features. The planet was divided into northern low plains and southern highlands that were pock-marked with craters. Mars had extensive elevated regions of volcanism, although no areas of fresh lava. There was weather: dust storms, pressure variations, and gas circulation between the poles. As NASA’s Thomas Mutch said of the Viking orbiter images, “They show Mars as an extremely diverse planet. . . . It is difficult to avoid the conclusion that, though Viking contributed immea­surably to breaking the code of the Mars enigma, we do not yet confidently understand its dramatic and turbulent past.”39

Most excitingly, Viking provided indirect but compelling evi­dence for water. Not currently—the air is so cold and thin that a cup of water placed on the surface would evaporate away in seconds. But the orbiters sent back images of rock formations all over Mars that could only have been produced by the action of

large amounts of liquid water in the past. Huge river valleys were seen, and places where it looked like rivers had once fanned out into a spider’s web of channels that ended in ancient shallow seas. The flanks of volcanoes had grooves that on Earth indicate water erosion. Many craters had shapes that were consistent with the impactor landing in mud. Other regions of chaotic terrain looked as if they had collapsed when underground volcanism melted ice, which then flowed away as water. The water flows implied by these features were equal to the greatest rivers on Earth (figure 2.2).40

In the sleepy community of Redlands, California, on the local li­brary shelves designated “Astronomy and Allied Sciences,” one book stands out for its well-worn, bent, and torn cover. It’s A Trav­eler’s Guide to Mars by planetary scientist William K. Hartmann. Advertised as an “extraordinary Baedeker,” the text is published in the format of the famous travel guide. Having sold so well the publisher reissued a second printing within the first two months of publication, the travel guide details features of the Martian surface. The adventures that await inside its pages include familiar and un­known craters, volcanoes, ancient river channels and flood plains, as well as the guide’s foldout maps, dramatic color photographs of key geographical locations, and sidebar articles on featured ter­rain. This isn’t a book for youth, but a serious guide for those in­terested in Mars. Readers are informed that they would be among the first to examine previously unpublished Mars Global Surveyor photos, as Hartmann served on the imaging team for that mission. His Martian travel guide offers serious analyses of geological for­mations in parallel with sidebars such as “What to Wear: A Look at Martian Weather.” Readers learn that typical daily temperatures span from -13°F during the afternoon to -125°F at night and that the extremely thin carbon dioxide atmosphere and low barometric pressure are inhospitable for human survival without protective gear. To familiarize travelers with the Martian night skies, Hart­mann explains: “The stars are brilliant at night after the glow of hazy sunsets fade, and the constellations are the same as the ones we see from Earth, with one exception: a blue-glowing ‘evening star’ with a faint companion ‘star’ is sometimes prominent for an hour or so after dusk.”36 One of Jim Bell’s panoramas, almost cer­tainly inspired by Carl Sagan, similarly captures from Gusev Cra­ter a view of our pale blue dot on the Martian horizon.

Travelers dulled by the “been there, done that” aspect of some Earth-bound excursions might consider the many fascinating des­tinations available via Google Mars, which offers virtual tours of Mars and commentary about major landmarks excerpted from Hartmann’s travel guide. Developed in collaboration with NASA by a Google team led by Noel Gorelick, and launched in 2009, Google’s virtual Mars was designed so that planetary scientists and general users might have ready access to a rich photo archive of past and current missions.37 Like Google Earth, click and zoom functions allow users to examine planetary features in 3D, as well as images from multiple NASA and ESA missions including Viking, Pathfinder, MER, Mars Global Surveyor, Mars Reconnaissance Orbiter, Mars Express, and Mars Odyssey Orbiter. Geographical and geological highlights are indicated with icons of two green mini-hikers, to reinforce Hartmann’s Baedeker motif. Users might follow the tracks of Spirit and Opportunity, locate the Viking land­ers, peer over the canyon rim into Valles Marineris, or alter the perspective to the canyon floor, from which Hartmann notes its walls can soar upward for 13,000 feet.

Even more stunning are the spectacular landscapes produced at the University of California, San Diego in what is called the StarCAVE, a 3D virtual, immersive environment the size of a large closet that allows researchers to explore stretches of Martian ter­rain. The MER rover pancams, developed through a collaboration of the NASA Ames Research Center, Carnegie Mellon University, and Google, produce high-resolution photos that can be config­ured as highly detailed 360-degree panoramas. The StarCAVE panoramas extend across the floor and to the ceiling so that plan­etary scientists can virtually explore the Martian landscape in situ to search for clues regarding soil deposition, wind and water ero­sion, and other geological processes. Using a hand-held device to navigate the immersive environment, researchers can zoom in to rock or sediment layers or zoom out to survey the broader lay of the land. Larry Smarr, who heads the California Institute for Tele­communications and Information Technology (Calit2) that oper­ates the StarCAVE, comments on the value of doing serious science in an immersive setting: “You can go into a room, and you’re on Mars.” He explains that the rendering is so fine that planetary sci­entists in effect can walk through the landscape, study rocks and geological features up close, as well as understand a site in relation to surrounding terrain.38

In the StarCAVE users must wear 3D glasses, but with the Per­sonal Varrier technology developed at the University of Illinois, Chicago, researchers can work in immersive virtual environments without any headgear, somewhat like the fictional holodeck pos­ited in the TV series Star Trek: The Next Generation. Even now re­searchers use this technology to engage with a variety of environ­ments, such as walking through the temples at Luxor, or exploring, from the inside, a molecule or a segment of the human genome. The public impact of these emerging virtual learning environments will be profound. Both NASA and the U. S. Congress are interested in using similar technologies to make planetary science more ac­cessible to everyone, so much so that the House of Representatives in its 2008 NASA Authorization Act invited the space agency to develop means by which general audiences can “experience mis­sions to the Moon, Mars, and other bodies within our solar sys­tem” through technologies such as “high-definition video, stereo imagery, [and] 3-dimensional scene cameras.”39 For now, Google Mars and the immersive environments of the StarCAVE or Per­sonal Varrier remind us that, whether in orbit or on the surface, our robotic partners precede us and increasingly unfold and make familiar nearby worlds.

“It is a drama as ancient as the sun, as unflinching as time. . . a never – ending whirl of celestial movements, scripted and precise, in a silent show of cosmic force, played out in light and shadow. It is a drama called equinox,” writes Cassini Imaging Team Leader Carolyn Porco in her “Captain’s Log,” an online diary of the Cas­sini spacecraft’s observations of the ringed world of Saturn and its moons. It takes approximately thirty years for Saturn to orbit the Sun, so the planet only experiences an equinox, when the Sun shines equally on its northern and southern hemispheres, every fif­teen years. In August 2009, equinox returned once again for Sat­urn as Cassini explored Saturn and its moons. “To its operators at significant remove, a billion miles away, it has been a long and gripping wait for this special season about to unfold. . . when the Sun passing overhead from south to north begins to set on the rings,” writes Porco. Observing Saturn in equinox from on site, she reminds us, is “a solemn celestial phenomenon no human has beheld before.”1

All of the large outer planets of our Solar System have rings, though none as magnificent as Saturn’s. The rings, no more than tens of meters thick yet spanning nearly 155,000 miles in diameter, come into sharp and rare relief during equinox when the angle of the Sun’s rays is lowered relative to the ring plane and casts long shadows across the rings (figure 5.1).2 In eloquent and poetic prose Porco comments, “Like the seas of Earth, this wide icy expanse

[ . . . ] froths and churns, not by wind but by the convulsive forces of Saturnian moons. This famous adornment, impressed deep in the human mind for four centuries as a pure, two-dimensional form, has now, as if by trickery, sprung into the third dimension.”3 Equinox on Saturn has since faded to northern summer and we along with Cassini have observed the clear, deep blue skies of Sat­urn’s northern hemisphere cloud over to reflect Saturn’s signature peach or faded orange hue. Robotic explorers like Cassini have given us entirely new perspectives of other worlds in the outer Solar System.

The comet cloud defines the outer edge of the Solar System, ex­tending a thousand times further than the planets from the Sun, and a significant fraction of the distance to the nearest stars. It had always been presumed that these small bodies were frozen rel­ics from the formation epoch, essentially unchanged in 4.5 billion years. The expectation was that comets would be made of dust from a previous generation of stars, or pre-solar grains. That’s why the mission was named Stardust.

Instead, something quite unexpected was found: fire and ice.24 Comets contain ice that formed in the frigid zone beyond Nep­tune, but the bulk of a comet’s mass is rock, and that rocky ma­terial seems to have formed under conditions hot enough to va­porize bricks. The comet particles embedded in Stardust’s aerogel included two ingredients that are found in meteorites, debris from asteroids that formed between the orbits of Mars and Jupiter. One is chondrules, rounded droplets of rock found in many primitive meteorites that melted and quickly cooled as they orbited the Sun. The other is a much rarer mineral called a Calcium Aluminum Inclusion, irregular white particles of very unusual chemical com­position that can only form at very high temperature. The Stardust team puzzled over this discovery, but the implication seemed clear. Matter that formed readily in the inner Solar System was some­how transported to the edge of the young Solar System where the comets formed. Wild 2 does contain grains of pre-solar stardust material, but they’re very rare. Comets are not made of material left over from other stars; they’re made mostly from material that formed close to the Sun. As such, they provide insights into how planets and moons were built 4.5 billion years ago.

Stardust’s primary contribution to planetary science is verifi­cation of the idea that there was extensive radial mixing of ma­terial in the solar nebula just as the Solar System was forming. Also, comets are more physically diverse and variegated than any­one imagined. Each of the comets where we’ve got up close and personal—Halley, Borrelly, Tempel 1, and Wild 2—have different shapes, surface textures and features, and levels of activity. Com­ets may be modest in size compared to planets and moons, but their role in planetary systems is anything but modest. They deliver water and organic building blocks of life to terrestrial planets, and as we know from studies of our geological record, when they hit a planet they can decisively alter the history of ecosystems and even the entire biosphere. It’s appropriate that all human cultures have been fascinated by comets, and viewed them as harbingers of life and death.

To learn more requires an increase in our modest amount of di­rect information. So it was very exciting when Stardust was given a new lease on life after its sample return. In 2007, NASA approved the New Exploration of Tempel 1 (NExT) mission, a return to the site of the Deep Impact mission in 2005.25 Stardust had con­served just enough hydrazine fuel to make a second journey to a comet, and the goal was to observe the impact made by the ear­lier spacecraft and see any changes on Tempel 1 caused by its last close approach to the Sun (Deep Impact’s cameras were blinded by dust released from the impact). In early 2010, a controlled burn ensured Stardust would approach at the optimal speed. The flyby was challenging because the camera had to catch the correct side of the tumbling comet nucleus while coming up on it at 7 miles per second. Appropriately, our first second date with a comet took place on Valentine’s Day, 2011. Stardust showed that the 500-foot wide crater created in 2005 was indistinct and had a mound in the center, indicating that much of the ejected material had fallen straight back down in the weak comet gravity. The results indi­cated that the comet nucleus was fragile and only weakly held together.

All good things must come to an end. For Stardust the end came on March 24, 2011, when mission controllers deliberately ordered a “burn to completion.” They told the spacecraft, which was al­ready running on fumes, to fire its main engines until there was no fuel left. NASA used the final burn to refine fuel consumption models for these kinds of engines, ensuring that Stardust gave use­ful data right up to its last gasp. The next day, Project Manager Tim Larson put the spacecraft into a state called safe mode, turned off the transmitter, and walked away from the console. Mission accomplished.

Michael Perryman has dubbed the Hipparcos mission astronomy’s equivalent of the Human Genome Project.22 Perryman explains that as astronomers more accurately map the location, velocity, and vector of stars in our galaxy we can understand the age and morphology of the Milky Way, how our galaxy has evolved in the past, and what the future holds for our Solar System and the gal­axy. For instance, the Hipparcos mission has contributed to our better understanding of the galaxy’s current structure. We know our galaxy is not a perfect spiral, but is instead a barred spiral that’s warped so that the limbs at one end curve up and at the other bend down (figure 8.3). Another major contribution of Hip – parcos, for astronomers and popular audiences, is that the mission improved the estimates of distances to stars harboring exoplanets. In this way, it has crystallized our sense of the growing number of distant worlds in space. We’ve seen in the earlier chapters on the Solar System that planets and moons are potential abodes for life. As the Human Genome is a project to map the underlying structure of terrestrial life, so Hipparcos is a tool to help astrono­mers map plausible sites for extraterrestrial life. The search for life beyond the Earth is a foundational scientific pursuit, and it has attracted attention from some unlikely quarters.

The Vatican has maintained an observatory over the centuries in order to officially determine dates of the calendar year; the Gre­gorian calendar has been used in the Western world since 1582. However, astronomers of the Vatican Observatory more recently

have been focusing on other concerns. In November 2009, Pope Benedict XVI called leading astronomers, astrobiologists, and cos – mologists to Vatican City to spend a week presenting recent find­ings regarding exoplanets orbiting nearby stars and to discuss the possibilities of intelligent life in those star systems.

Of the Vatican’s interest in exobiology, science reporter Marc Kaufman noted: “Just as the Copernican revolution forced us to understand that Earth is not the center of the universe, the logic of astrobiologists points in a similarly unsettling direction: to the likelihood that we are not alone, and perhaps that we are not even the most advanced creatures in the universe. This. . . may conflict with the stories we tell about who and what we are.”23 During the five-day meeting scientists addressed subjects such as the origins of life, extremophiles and their habitats, the likelihood of such life thriving on moons in the outer solar system, and whether life’s bio­signatures could be detected on exoplanets.

As yet, exoplanets are mostly gas giants with little chance of life on them, but as the detection limit has reached Earth mass with NASA’s Kepler satellite, research spurs scientists, philosophers, and theologians alike to contemplate the implications for our place in the universe. “The questions of life’s origins and of whether life exists elsewhere in the universe. . . deserve serious consideration,” explained Jose Gabriel Funes, a Jesuit priest who is also the di­rector of the Vatican Observatory. Co-author Chris Impey, who presented a paper at the meeting and co-edited the written pro – ceedings,24 comments: “Both science and religion posit life as a special outcome of a vast and mostly inhospitable universe. There is a rich middle ground for dialog between the practitioners of as – trobiology and those who seek to understand the meaning of our existence in a biological universe.”25 Reporter David Ariel, who also covered the meeting, aptly noted, “The Church of Rome’s views have shifted radically since Italian philosopher Giordano Bruno was burned at the stake as a heretic in 1600 for speculating, among other ideas, that other worlds could be inhabited.”26

For the moment, most of the vast inventory of stars remains out of reach. But several hundred relatively nearby stars are known to have planets, and Hipparcos has been an essential tool in measur­ing their distances. These new and potentially habitable worlds range from a dozen to a few hundred light-years away. Spanning the entire galaxy, one estimate is of 8 billion terrestrial habitable worlds around Sun-l ike stars, each of which has the potential to host life.27 This number is the same order of magnitude of the number of base pairs derived from the Human Genome Project, making literal the analogy of a vast mapping project to parse life in the Milky Way.

The grip that Mars holds on the popular imagination is grounded in the question of whether Mars ever was, or is, alive. The Viking landers were explicitly designed to search for evidence of life in the Martian regolith or perhaps in the planet’s geological past.41

The short section of the mission science summary on life detection is worth quoting in full because of the surprising ambiguity of the wording: “Three experiments were conducted to test directly for life on Mars. The tests revealed a surprisingly chemically ac­tive surface—very likely oxidizing. All experiments yielded results, but these are subject to wide interpretation. No conclusions were reached concerning the existence of life on Mars.”42

The Viking landers packed a substantial scientific punch in their 200-pound payloads. Power came from a plutonium-238 radioiso­tope thermal generator, eking out 30 Watts of continuous power. Using late 1970s technology, Viking’s data capabilities were even more feeble; the data recorder on each lander could only store 8 Mbytes at a time, thousands of times less than the average mem­ory stick. The landers had cameras that could take 360-degree panoramic images. They had seismometers and instruments to test magnetic fields. They had meteorology booms that measured temperature, pressure, and wind speed and direction. Most impor­tantly, they had robotic arms that could scoop up soil samples and deposit them into temperature-controlled and sealed containers on each spacecraft (figure 2.3).

The biological package contained four instruments. A gas chro­matograph and mass spectrometer heated soil samples and mea­sured the molecular weight of each component of the vapor re­leased, down to a concentration of a few parts per billion. The instrument found no significant levels of organic, or carbon-based, molecules. Mars soil had even less carbon than the lifeless soils tested on the Moon by the Apollo missions. This seemed to be prima facie evidence against life. The gas exchange instrument added nutrients, and then water, to a soil sample, and then looked for changes in the concentration of gases such as oxygen and methane in the sealed chamber. The hypothesis was that a living organism would process one of the gases. The result was negative. The pyrolytic release experiment created an “atmosphere” in the chamber using radioactive carbon, in the hope that a photosyn­thetic organism would incorporate the carbon the way plants do on Earth. After several days of incubation under an artificial Sun (in this case, a xenon arc lamp), the sample was baked at a high temperature to see if any of the radioactive carbon had been con­verted into biomass. The results were also negative.43

The only wild card was the labeled release experiment. A sample of soil had nutrients dissolved in water added to it, and the nutri­ents were “tagged” with radioactive carbon, which was once again used as a tracer. To the surprise of the instrument team, radioactive carbon dioxide was detected in the air above the samples, suggest­ing that microbes had metabolized one or more of the ingredients. The same result was seen in both Viking landers. However, when the experiment was repeated a week later, the air was free of radio­active carbon. The data were declared inconclusive.44

Overall, the results were disheartening for those who hoped that Mars might be a living world. Terrestrial life is based on com­plex molecules with a carbon backbone—organic ingredients like carbohydrates, proteins, nucleic acids, and lipids. While organic does not mean biological, all life on Earth is carbon-based and so is made of organic ingredients. The Viking experiments detected virtually no organic compounds in the Martian regolith. This was somewhat surprising, since they are fairly common on small Solar System bodies like comets, asteroids, and meteorites. With no organic material, the biological experiments would have been doomed to failure, since their aim was to detect a metabolism that could incorporate carbon from the atmosphere, as microbes on Earth do. The lander could only gather samples from the top few centimeters of the regolith, and that layer is blasted with ultravio­let radiation and cosmic rays from space (Mars has no protective layer of ozone). The surface is strongly oxidizing, as the “rusty” red color of iron oxide indicates.45 So the conventional interpreta­tion is that activity seen in the experiments was caused by chemical reactions involving oxidizing molecules in the soil, with no bio­logical explanation required.

Former NASA historian Steven Dick recounts the claims, first, by American physicist Nikola Tesla and a few decades later by Ital­ian innovator of wireless telegraphy Guglielmo Marconi that they had received wireless signals from Mars. Collier’s Weekly in 1901 reported that Tesla was convinced he was “the first to hear the greeting of one planet to another” and that the supposed radio signals were most likely from Mars.40 By the early 1920s, Marconi apparently repeatedly attempted to receive short-wave radio mes­sages from Mars. Dick writes: “Marconi’s interest in interplanetary communication peaked during a trip from Southampton, England, to New York City aboard [his yacht] the Electra from May 23 to June 16, 1922. The New York Times noted that Marconi ‘spent the time crossing the Atlantic performing many electrical experiments, principally by listening for signals from Mars.’”41 William Sheehan and Steven O’Meara report that two years later, when Mars was at its closest since 1804, “radio stations around the world were urged to simultaneously cease transmissions at specified intervals, so as not to interfere with any attempts by Mars to radio the Earth.”42 Even the U. S. Navy, notes Dick, monitored radio transmissions for potential Martian messages.

News reportage of such events may be the reason so many as­sumed a Martian invasion in October 1938 when a radio broad­cast, seemingly interrupting The Mercury Theatre on the Air pro­gramming, indicated Martians had landed at the Wilmarth farm in Grover’s Mill, New Jersey. Orson Welles’s radio presentation, discussed in chapter 1, is one of the most singular events in radio history. As Bruce Lenthall points out, broadcast radio was a major news source in the early twentieth century. For audiences in the United States, Lenthall claims: “Radio ownership more than dou­bled in the 1930’s, from about 40% of families at the decade’s start to nearly 90% ten years later. By 1940 more families had radios than had cars, telephones, electricity, or plumbing.”43 Len – thall estimates that 6 million people actually heard the radio play that Howard Koch adapted from H. G. Wells’s The War of the Worlds (1898) and of that number, approximately 1 million listen­ers literally thought Martians had landed. Subsequent to Tesla and Marconi’s independent claims of having detected radio messages from Mars, some contemplated whether Mars was inhabited by a sophisticated civilization whose radio signals the authorities had been listening for. T. S. Eliot noted in the poem “The Dry Salvages” (1941) that popular commentary on means to “communicate with Mars” was one of the “usual [p]astimes.”44

Perhaps interplanetary travel from Mars didn’t seem entirely fantastic given that the twentieth century emerged as an unprec­edented era of global travel. In the first few decades of the cen­tury, train and ocean liner travel expanded exponentially, while motoring, and flight, first achieved in 1903, quickly developed as everyday experiences. Large numbers of people became mobile in ways that just a few years prior had been extremely arduous, or even unimaginable. With the serious development of rocketry in the 1920s and the genesis of the American Interplanetary Society in 1930, followed by the British Interplanetary Society in 1933, travel between Mars and Earth may have finally seemed possible and well within the realm of the imagination.

With large numbers for the first time traversing multiple time zones in a day, British author Virginia Woolf suggested that people began to internalize in finer detail Earth’s global topography. She claimed that her own travel experiences afforded her a better sense of Earth’s surface so that she could easily imagine and rehearse its large topographical contours. When she and her husband Leonard bought a used automobile from sales of her novel To the Light­house (1927), Woolf observed that motoring had been “a great opening up in our lives” that allowed her to “expand that curious thing, the map of the world in ones [sic] mind.”45 As early as 1909, while traveling through Italy, Woolf recorded in her diary: “It is strange how one begins to hold a globe in ones [sic] head; I can travel from Florence to Fitzroy Square [in London] on solid land all the time.”46 She meant that she could easily envision the con­tours of Earth’s globe, as if she could turn the Earth around in her fingers and trace its continents, mountains, islands, and shorelines.

Coincident with the increase in global travel in the first few decades of the twentieth century was the construction of a new generation of large telescopes like the 100-inch at Mount Wilson Observatory. News reports covering astronomical discoveries fre­quently appeared in newspapers and weeklies, so much so that references to lunar and planetary landscapes were taken up in advertising and in the common parlance. In January 1926, while motoring through Persia, Woolf’s close friend and celebrated au­thor Vita Sackville-West wrote to Virginia describing the hills near Thebes in Egypt as a “mountains-of-the-moon landscape.” A year later, in March 1927, Sackville-West was again touring in Persia and wrote to Woolf from Tehran, “[T]here is one little asteroid, called Ceres I think, only four miles across, the same size as the principality of Monaco, on which I have often thought I should like to live, revolving in lonely state round the Sun.”47 Presum­ably Sackville-West had read a news report regarding our larg­est asteroid, currently estimated at 975 kilometers or 606 miles in diameter. Prompted perhaps by Vita’s evocation of other plan­etary landscapes, Woolf in September that year noted in her diary: “What I like. . . about motoring is the sense it gives one of light­ing accidentally, like a voyager who touches another planet with the tip of his toe, upon scenes which would have gone on, have always gone on, will go on, unrecorded, save for this chance glimpse.”48 Decades later, Spirit and Opportunity offered our first extensive, close-up glimpse of Martian geological processes that have gone unrecorded for eons, and what we have found allows us to more fully internalize the red planet’s landscapes and its geomorphology.

Saturn’s ring system became etched in the human imagination some time after the mid-1600s when Dutch mathematician and astronomer Christiaan Huygens first illustrated the rings.4 He also was first to identify its moon Titan.5 However, in recent memory, it was Chesley Bonestell’s renderings of Saturn that brought the planet into the public purview. By training Bonestell was an ar­chitect, but he’s probably best known for the stunning paintings of Saturn published in May 1944 in LIFE magazine. The most famous and striking of these is titled “Saturn as Seen from Titan.” Readers were amazed by the suite of paintings that appeared in the May 29 issue, perhaps in part because the issue was largely dedicated to news and advertisements related to the war effort. Among 130 pages of news reports on American soldiers in Europe, war-themed ads, and largely black and white photos of troops, Bonestell’s realistic and full color renderings of Saturn lumbering in the sky of Titan transported readers into exotic and delightful planetary vistas.

Bonestell recounted how in 1905 he was inspired to paint the spectacularly ringed planet: “When I was seventeen, an important event occurred in determining my future career, although I little suspected it then.” Having once hiked with a friend to Lick Ob­servatory at the summit of Mount Hamilton, Bonestell recalled, “That night I saw for the first time the Moon through the 36-inch refractor, but most impressive and beautiful was Saturn through the 12-inch refractor. As soon as I got home I painted a picture of Saturn.”6 Although that painting was lost in the fires caused by the Great Earthquake of 1906 in San Francisco, Saturn had made a lasting impression on the young artist.

When nearly forty years later Bonestell submitted the series of paintings that included “Saturn as Seen from Titan” to the edi­tors of LIFE, they quickly agreed to publish them. Ron Miller and Frederick Durant explain: “No one had ever before seen such paintings—they looked exactly like snapshots taken by a National Geographic photographer (figure 5.2). For the first time, renderings of the planets made them look like real places and not mere ‘art­ists’ impressions.”7 Miller and Durant write that Carl Sagan main­tained “he didn’t know what other worlds looked like until he saw Bonestell’s paintings,” while science fiction writer Arthur C. Clarke suggested that in a sense Bonestell had walked on the Moon long before Neil Armstrong and reportedly quipped, “Tranquility Base was established over Bonestell’s tracks and discarded squeezed-out paint tubes.”8

Wyn Wachhorst has explored why Bonestell’s famous painting “Saturn as Seen from Titan” is so compelling: “Since Titan is the only satellite in the Solar System with an atmosphere, the giant Saturn looms low in a dark blue sky like an alien ship, a thin,

gleaming crescent bisected by the glowing edge of its rings, afloat between jagged cliffs that jut from a frozen sea. . . . A hint of dawn lights the far horizon; and beyond a lofty pinnacle, out under the glow of the great crescent, lies a distant patch of noonday plain.” Among the other Bonestell paintings in the LIFE layout were imagined scenes of Saturn from its moons Phoebe, Iapetus, Mimas, and Dione. One depicted Saturn’s rings passing overhead from the perspective of the planet’s cloud tops. Wachhorst explains that the suite of paintings was intended to offer varying views of Saturn on approach from its outer moons.9

Though he painted numerous panoramas of planetary land­scapes ranging from Mercury to Pluto, Bonestell was aesthetically captivated by Saturn, a subject he repeatedly returned to through­out his life. He painted numerous iterations of Saturn from Titan and its other moons. In 1949, for instance, he completed paintings of Saturn from Dione, in which the full body of Saturn is glimpsed from the mouth of a cave. His panorama for the Griffith Observa­tory, completed in 1959, featured a prescient vision of the frozen landscape of Titan with Saturn low on the horizon. Throughout the 1960s, Bonestell reworked different views of Saturn from Titan, changing the lighting or subtly altering Titan’s landscape. In 1972, he completed two separate paintings of Saturn from Iapetus, as well as a painting of Saturn from Enceladus for Arthur C. Clarke’s book Beyond Jupiter. Bonestell returned to the subject of Saturn again and again, in various configurations, settings, and lighting.

All this from an architect whose work included contributions to the design of San Francisco’s Golden Gate Bridge, the layout of the well-known Seventeen Mile Drive at Pebble Beach in Monterey, the Eagle gargoyles and art deco facade of the iconic Chrysler building in New York City, and the design of buildings for the Cal­ifornia Institute of Technology in Pasadena.10 He became the high­est paid special effects artist in Hollywood, working on films like The Hunchback of Notre Dame (1939) and Citizen Kane (1941). Bonestell’s turn to space art played out in popular magazines such as LIFE and Collier’s, and in films like Destination Moon (1950), When Worlds Collide (1951), and Conquest of Space (1955). His work inspired generations to imagine the stark and beautiful plan­etary landscapes in our Solar System and in far-flung star systems of the galaxy. “Bonestell brought the edge of infinity out of the abstract and into the realm of direct experience,” comments Wach – horst.11 His paintings suggested planetary vistas human eyes had not yet seen, and sometimes included figures of astronauts dwarfed by a vast surrounding terrain. This was true of his painting of Sat­urn from Mimas in the LIFE layout, and of an iteration of Saturn from Titan completed in 1969, which situates three tiny astronauts on a cliff, looking out at a fully lit Saturn as one astronaut points to the rings.

Bonestell apparently learned the technique for rendering his realistic paintings from science illustrator Scriven Bolton while working in the 1920s at the Illustrated London News. Bolton, a Fellow of the Royal Astronomical Society, constructed plaster cast models of planetary landscapes, photographed them, and then painted in planets and stars.12 Working from this technique, Bon – estell would project light onto his plaster landscapes to get a sense of how sunlight and shadows might fall across terrain, and then painted based on photos of these lit scenes. This resulted in land­scapes that seemed reachable and tangible. His widely celebrated renderings “invited viewers into the possible planetary landscapes that exist on moons of the outer solar system. In Bonestell’s depic­tion, Titan’s landscape resembles that of the American Southwest or perhaps the craggy cliffs of the Rocky Mountains in winter. The deep blue of the sky recalls that of Earth.”13 Though such spectacular views from Titan may be unlikely given the moon’s hazy, methane-rich atmosphere, Bonestell was prescient in suggest­ing the sublime experience of standing on the shore of one world to view another in close proximity.

Wyn Wachhorst contends that Bonestell’s art purposely evokes “a kind of cosmic shoreline, a composite of stark and eerie beaches on the near edge of the starry deep,” and that the seashore is the “root metaphor” of Bonestell’s art, meant to evoke Earth’s hori­zon as the shoreline between Earth and outer space. Bonestell’s art reminds us that from Earth we stand “on the shore of the cosmic ocean, riding our wisp of blue and white like mites on a floating leaf, in the whorls and eddies of a great galactic reef.”14 Carl Sagan wrote in Pale Blue Dot that humans have from time immemorial been innately drawn to the horizon. Ancient Egyptians identified their god Horus with the Sun on the horizon and with the planet Saturn, thought to represent Horus the Bull.15 The Great Sphinx in Giza apparently was associated with Horus and specifically is ori­ented toward, and draws the eye to, the Eastern horizon.16 With­out question, Bonestell’s work inspired Sagan, whose first episode of the PBS series Cosmos was titled “The Shores of the Cosmic Ocean.”

In August 1929, the New York Times science section ran an article titled “The Star Stuff that is Man.” Astronomer Harlow Shapley had been popularizing the point that humans are the mere by­products of stars. In a radio talk series a few years earlier produced by the Harvard College Observatory, Shapley pointed out that “we are made out of the same materials that constitute the stars.”26 In the Times article, Shapley similarly observed: “We are made of the same stuff as the stars, so when we study astronomy we are in a way only investigating our remote ancestry and our place in the universe of star stuff. Our very bodies consist of the same chemical

elements found in the most distant nebulae.”27 At the time, some were disconcerted to think that humans might be little more than the product of fission and fusion occurring in stars.28

Cosmologists have good evidence that all the hydrogen and most of the helium in the universe have existed since close to the time of the big bang. Hydrogen, the simplest element, is truly primor­dial, while most of the helium was formed soon after in a process known as primordial nucleosynthesis or big bang nucleosynthe­sis. “The primordial nuclei of the matter constituting the universe were formed in the first three minutes,” explains CERN theoretical physicist Luis Alvarez Gaume. “The cosmic oven produced a num­ber of nuclei, made up of about 75% hydrogen and 24% helium. Small amounts of deuterium, tritium, lithium and beryllium were also produced, but hardly any of the other atoms that make up our bodies and the matter around us: carbon, nitrogen, oxygen, sili­con, phosphorus, calcium, magnesium, iron, etc. All of these were formed in the cosmic ovens of subsequent generations of stars. As Carl Sagan put it, we are just stardust, remains of dead stars.”29

The Oxford English Dictionary lists a definition for the term stardust as “fine particles supposed to fall upon the Earth from space; ‘cosmic dust.’” The OED likewise cites one published com­mentary from 1879 that claimed “the very star-dust which falls from outer space forms an appreciable part” of the mud accumu­lated on the ocean floor.30 In fact, the estimate for interplanetary dust particles swept up each year by the surface of the Earth as it churns through space is a substantial 10,000 tons, but that’s a tiny fraction of the material added to the seafloor. The most pristine reservoirs of stardust or interplanetary dust are comets. Having formed early in the life of our Solar System approximately 10 mil­lion years after the Sun’s protoplanetary disc stabilized, comets spend most of their time in the cold extreme outskirts of the Solar System. As a result, comet nuclei are largely preserved from heat­ing, melting, and collisions with other planetary bodies. The ice composition and dust grains of comets reveal elements present in the Solar System’s primordial past.

Nuclear fusion reactions in stars create heavier elements by pro­cessing or fusing together lighter atomic nuclei. The base of the fusion “pyramid” is the fusion of hydrogen into helium, which oc­curs in the Sun and low-mass stars. Stars approximately the mass of our Sun can also synthesize helium, carbon, and oxygen, but thereafter, they never reach a dense enough or hot enough state to fuse yet heavier elements. Massive stars have the ability to fuse their hydrogen to produce helium, carbon, and oxygen, but then progress in successive stages of evolution to neon, magnesium, sili­con, sulfur, nickel, and iron. Iron is the most stable element, so typ­ically the fusion chain stops there. Still heavier elements are forged two ways: by the slow capture of neutrons in the atmospheres of massive stars and more rapidly by stellar explosions known as novae and supernovae.31 Since rarer, larger mass stars are required to generate the heaviest elements, these elements are cosmically scarce compared to the light elements hydrogen and helium.

The first generation of stars probably formed approximately 200-300 million years after the big bang.32 According to cur­rent theoretical ideas, none of those stars still exist and certainly none have yet been found. They have since exploded in novae or massive supernovae, collapsed into black holes, or have oth­erwise expended their fuel and burned out. The oldest stars cur­rently are generations removed from the first stars that shone in the universe.33 Astronomers estimate that approximately twenty – five novae occur each year in an average galaxy generating inter­stellar dust enriched with heavier metals. From the clouds of gas, dust, carbon, silicon, and metals produced by repeated generations of novae and supernovae, new stars and their attendant planets are born.

A nova is a sudden brightening of a star believed to occur when the outer layers of a star are pulled by gravity onto the surface of a companion white dwarf. Pressure due to the mass that accumu­lates on the white dwarf causes nuclear fusion of hydrogen into he­lium at its surface that in turn blows material off the surface of the white dwarf. One type of supernova is an extreme form of a nova, where mass acquired from a young companion star causes a white dwarf to begin carbon fusion and explosively detonate. Another type, a core collapse supernova, occurs when a single massive star exhausts its nuclear fuel and suffers a core collapse followed by explosive detonation. In comparison to a nova, a supernova will produce a million times the energy and can for weeks shine as brightly as all the stars of an entire galaxy. In the case of the Milky Way, that’s equivalent to about 400 billion Suns. A supernova is a prodigious alchemical event; one that detonated in a nearby gal­axy in 1987 generated enough stardust to build 200,000 Earths.34

The Milky Way formed approximately 10 billion years ago, but our Sun is only 4.5 billion years old. The Sun and its neighbor­ing stars were likely born in a nearby region of dense, coalescing interstellar gas and dust. Isotopic studies of meteorite samples in­dicate that our Sun formed from the detritus of a massive super­nova explosion in nearby space roughly 1 million years prior to the formation of the protoplanetary disc that became our Solar System.35 We know this simply by the presence of metals that our Sun could not have produced, such as the iron that makes up the Earth’s core. Other than hydrogen, which is primordial and dates back to cosmic genesis, almost all the other atoms in the universe have been recycled, silent witnesses to amazing trips through fiery cauldrons and into frigid space, some experiencing multiple adven­tures. Unfortunately, no atom bears the imprint of its particular passages through the core of a star; astronomers can only describe the origins statistically.