Five Billion Years of Solitude (22 page)

Out of Equilibrium

A
n earth scientist’s tendency to see the Big Picture at the expense of smaller details helps explain something that happened to me one morning in the red-brick Deike Building that houses the Marcellus Center and Penn State’s geosciences department. I was standing next to a bank of elevators in an otherwise empty corridor, waiting to meet someone. A short, bespectacled man in a button-down flannel shirt and khaki pants rounded a corner, glanced at me as he walked past, and entered a nearby bathroom. A minute passed, then the man reemerged and walked by me again, pausing to sip from a water fountain before making to return down the hall. When he was a few steps from vanishing around the
corner, I called out to him, and when he turned around to look he didn’t seem to immediately recognize me.

I was surprised, since I recognized him as Jim Kasting, a geosciences professor at Penn State specializing in the evolution of Earth’s atmosphere and climate. After more than two hours of conversation in a noisy bar/restaurant called “Mad Mex” the previous evening, we had agreed to meet that morning to talk more about his work. I had spoken with him on the phone minutes earlier when I had arrived at Deike, but when he passed me twice in the hall I might as well have been one of the specimens of sedimentary rock in the glass cases that lined the wall.

“Oh,” he said at last. “Hi, Lee. Didn’t see you there. Let’s go into my office.”

Picture a NASA astronaut—not so much the stereotypical fighter-plane jock from the Space Race, but the post-Apollo variety, a straitlaced fitness buff with an advanced academic pedigree—and you probably have summoned a good approximation of Jim Kasting. Kasting is fifty-eight but looks years younger thanks to a strict regimen of swimming, running, and weight lifting. He is bookishly handsome, with a wide, magisterial forehead and the compact, sinewy build of a wrestler. He is equally at home discussing either the finer points of planetary carbon cycles or the benefits of rear-wheel drive on sports cars. Kasting speaks with clipped precision, and emotion rarely shades his voice. He never seems to be in any big hurry yet manages to be monumentally productive. His most astronautical quality, however, is something more subtle: a serenity that suggests awareness of one’s inescapably small place in the world, an acceptance awakened by long hours spent contemplating the Earth from some lofty perch.

Kasting’s resemblance to an astronaut was apt given his upbringing, which we had discussed over a cacophony of drunken Penn State coeds and a dinner of one-dollar tacos the previous night. He and his identical twin brother, Jerry, were born in Schenectady, New York, in the wee hours of January 2 in 1953. A younger sister, Sandy, arrived years later. His mother stayed at home raising her children, though she
would later use her degrees in chemistry and mathematics to teach college courses. His father was a mechanical and electrical engineer, building jet engines as a subcontractor for General Electric. The family rarely stayed one place long, as GE moved them around the country to wherever the next contract was—first Schenectady, then Cincinnati, then Schenectady again—until 1963, when the family moved to Huntsville, Alabama, where they would stay for the next seven years. This contract was for something entirely new in the world, particularly for the Kasting brothers, who were in the midst of fifth grade: GE had sent their father to Alabama to work on third-stage engines for NASA’s giant Saturn rockets.

In the 1960s Huntsville was a town dominated by the early promise of the Space Age. The rockets for America’s first ballistic missiles, satellites, and astronauts had been developed at the nearby Redstone Arsenal, and most Huntsville families put their food on the table, directly or indirectly, with space-program funds. Out at a restaurant for supper, they might look over to see Wernher von Braun, the chief architect of the Apollo program, seated at an adjacent table dourly tearing into a steak. When they went home and watched the nightly news, von Braun would be there again on the television screen, speaking in Teutonic tones about the new high frontier. He headed NASA’s Marshall Space Flight Center some twelve miles southwest of Huntsville. When every now and then Jim and Jerry would see a line of black limousines speeding through town, they knew another VIP federal motorcade was bound for Marshall and von Braun. America was going to the Moon, and the world seemed poised at the brink of a new revolutionary era. But the boys didn’t truly appreciate the magnitude of their father’s work until Huntsville began to regularly quake for minutes at a time. Bolted to static test stands down at Marshall, the Saturn rocket’s great engines were being put through their paces, combusting huge reservoirs of liquid hydrogen and oxygen to produce millions of pounds of thrust per second. Each test firing began with a deep rumble that quivered the dogwoods and magnolias and clouded the sky with startled
birds. The rumble rapidly crescendoed into a sustained roar that rolled beneath and through the town, cracking windowpanes and windshields and stirring a yearning in young Jim to, someday, work for NASA, if not as an astronaut, then maybe as a scientist. The roar of rockets signaled a future where humanity’s fortunes would be found beyond Earth’s cradle.

Kasting began working hard in math and science at school, and read all the science fiction he could get his hands on. One of his favorites was Isaac Asimov’s Foundation series, books about the rise and fall of a galactic empire. Much of the story revolved around the empire’s capitol planet of Trantor, a stand-in for what, at the time, passed as a plausible guess at Earth’s not-too-distant future: a planet where land and sea, where nature itself, had been wholly smothered and subdued beneath the footprints of forty billion people and a glittering techno-utopia of skyscrapers, superhighways, and domed farms and habitats. “I liked books with big ideas, ones that dealt with the future of humanity, or how to run a society,” Kasting told me. “
Foundation
had a cool one: ‘psychohistory,’ the idea that if you have enough people they will behave just like atoms or molecules, individually unpredictable but foreseeable in aggregate, so a civilization’s behavior becomes like that of an ideal gas, something controlled through statistical mechanics. I don’t know if that’s true—people are pretty complicated—but it made me think more about what can be predicted.”

Late one evening when the boys were in middle school, Kasting’s father arrived home from work with a tripod-mounted 2.5-inch refractor telescope, suitable for viewing all that the new rockets were bringing into reach. On dark, clear nights, they could see Saturn’s rings, the ruddy disk of Mars, and the plains and craters of the Moon where men soon would walk. Through the viewfinder, the jagged, magnified lunar surface looked close enough to touch, like some monochrome impasto landscape hung on a museum wall. Jim’s interests exceeded the limits of the solar system a few years later when he upgraded to a more powerful 4.25-inch reflector, and he began searching the sky for nearby
planetary nebulae and neighboring galaxies. Sometimes he would wonder how the Earth or another inhabited world would appear, viewed from so very far away, if only there was a telescope big enough to look.

After high school, Jim plotted a trajectory he hoped would intersect with NASA’s orbit: undergrad at Harvard, then a PhD in atmospheric science at the University of Michigan, and finally a series of postdoctoral positions. In 1981, he achieved his dream, securing a research fellowship at NASA’s Ames Research Center in Mountain View, California.

Not long after Jim’s NASA debut, his father paid him a visit out in California. By then, Jim had met and married his wife, Sharon, and their first child, a son, Jeff, had just been born. Kasting’s father listened attentively, smiling and nodding as Jim showed off his burgeoning efforts to model the early atmospheric evolution of Venus, Earth, and Mars—working on the problems full-time with NASA’s winds at his back, he was making progress fast, and getting further than anyone had before. Perhaps skeptical that Jim could raise a family by predicting a planet’s far-distant past and future, or maybe just habituated to always push for greatness, when Jim had finished explaining Kasting the elder promptly asked his son when he planned to get a real job. In fact, Kasting’s work had already begun to revolutionize planetary science and had placed him on the NASA fast track. In 1983, when his fellowship expired, he was immediately hired as a research scientist at Ames, where he would remain until his 1988 emigration to Penn State. With NASA money as their nest egg, Jim and Sharon would have two more sons, Patrick and Mark.

Kasting’s Penn State office was adorned only with a blue-and-white Oriental rug and a few yellowing astronomy-themed posters that broke the spartan regiments of books, papers, and reports. One side of the room was occupied by three large filing cabinets, collectively filled with a good half ton’s worth of astrobiology’s primary literature. The other side was taken up by bookshelves mounted on the cinderblock
walls. The shelves brimmed with well-thumbed, dog-eared volumes with such titles as
Biogeochemistry of Global Change
,
The Chemical Evolution of the Atmosphere and Oceans
, and
Fundamentals of Atmospheric Radiation
. An adjacent whiteboard was filled top to bottom with scribbled shorthand references to stellar flux, atmospheric partial pressures, and surface temperature, as well as three frenzied, overlapping strata of differential equations, each distinguished by its own shade of erasable marker.

The books and equations revealed Kasting’s true interests, which go far beyond our own small planet and its history, harking back to his musings at a backyard telescope. He is widely considered the world’s foremost authority on planetary habitability—how a life-friendly planet can emerge and evolve over geologic time. Like the Earth itself, he has spent most of his time within the Precambrian’s murky frontiers. Among other things, he has had a hand in calculating how much longer photosynthesis can support complex life on Earth (about a billion years), the minimum size an impacting asteroid must be to vaporize Earth’s oceans (one 270 miles wide would do the trick), and whether by burning all available fossil fuels humans could force the Earth into a Venus-style runaway greenhouse (the jury is technically still out, but Kasting believes the answer is, thankfully, “no”).

Over dinner the night before, I had suggested that we hike through some of the surrounding Pennsylvania wilderness, so that Kasting could use examples from the landscape to illustrate his Big Picture view of Earth as a system, of habitability as a process unfolding over geologic time. “If you take me out in the field, I’m pretty useless,” he initially demurred. “I’ve actually had no formal education in geology. I probably couldn’t tell you if a rock was a carbonate or a silicate. I’d be lucky to know a glacial till from a landfill.” After finishing a margarita, he had changed his mind, and offered to take me to Black Moshannon State Park, five square miles of forest and wetland located a twenty-minute drive northwest from Penn State’s campus. “I still won’t be very useful,” Kasting said, “but it will be a nice walk.”

•   •   •

B
ehind each modern announcement that scientists have found yet another possibly habitable world is a well-worn process that, simplified, unfolds as follows: Astronomers first measure the newly discovered planet’s mass, and, if possible, its radius, generating an estimate of the planet’s density and its likelihood of being rocky like the Earth. They also determine the rocky planet’s orbital distance from its star, as well as the intensity and color of the star’s light. Armed with this scant data, the entirety of which you could jot in ballpoint pen on the palm of one hand, they then interpret it through numerical modeling. In particular, they consult one of Kasting’s most-cited papers, “Habitable Zones around Main Sequence Stars,” published in the journal
Icarus
in 1993. In that paper, Kasting and two colleagues, Dan Whitmire and Ray Reynolds, used a climate model developed by Kasting to determine which orbits around stars are most likely to allow rocky planets to harbor liquid water upon their surfaces. Inward of the habitable zone, a planet’s surface would be so scorched that any water would flash to steam, suffusing the atmosphere and gradually escaping into space, similar to what occurred on Venus; outward of the zone, a planet’s surface water would freeze, similar to what we see on Mars. If a newfound rocky planet proves to be within Kasting’s habitable zone, shortly thereafter its discoverers contact their funding institution’s press office, and soon their names appear on the nightly news and in the
New York Times
. Kasting coauthored a paper in January 2013 gently revising his twenty-year-old calculations, but the tweaks did not greatly alter his earlier work’s core conclusions.

Using a literal handful of data points to estimate the habitability of a faraway planet is a practice fraught with uncertainty, where major assumptions and leaps of faith become inevitably routine. That it is possible at all is only because, as far as we can tell, the laws of nature are everywhere the same throughout our observable universe, whether in the solar system or around some far-distant alien star. Anywhere in the
universe where starlight falls upon a planet, it pumps radiant energy into the system of that world. How much energy filters in depends on the planet’s atmosphere, and upon the starlight’s wavelength, or color. For those canonical 1993 calculations, Kasting and his colleagues gave their virtual planets atmospheric compositions thought to be the most typical outcome of terrestrial planet formation: lots of inert nitrogen, accompanied by substantial fractions of CO
₂
and water vapor. Evidence suggests this was the bulk atmosphere of the early Hadean Earth, but for distant rocky exoplanets with atmospheres that have yet to be measured, any particular mix can presently be seen as only a hopeful guess.