I headed downstate, to the flagship public school. There I took a biology survey picked at random out of the course catalog to meet a general education requirement. It was taught by a bacteriologist name Katja McMillian. She was cylindrical and stork-like, a super-annuated Big Ethel Muggs. But Mondays, Wednesdays, and Fridays, she stood in a bowl of four hundred undergraduates, on fire. Week after week she worked to show us how none of us had a clue what life could do.
There were creatures that retooled themselves into something unrecognizable halfway through their life. There were creatures that saw infrared and sensed magnetic fields. There were creatures that changed sex based upon straw polls of the neighborhood, and single cells that acted en masse by sensing quorums. Lecture by lecture, it dawned on me: Astounding Stories had nothing on Dr. McMillian.
In week twelve, almost through the semester, she arrived at the creatures she loved. A revolution was under way, and Dr. McMillian was on the barricades. Researchers were finding life where science knew it could not live. Life was eking out a living above the boiling point and below freezing. It staked out places Dr. McMillian’s own professors once insisted were too salty, too acidic, and too radioactive for any creature to survive. Life made a home high up on the edge of space. Life lived deep in solid rock.
I sat in the back of the auditorium thinking: My people. At last.
Dr. McMillian hired me to assist on a summer field expedition to study alien life-forms in a sinkhole under Lake Huron that someone had discovered by accident. They were among the most bizarrely creative creatures on this planet—switching like Jekyll and Hyde from anoxic to oxygenic photosynthesis when the tasty sulfur ran out. The crazy biochemistry behind Dr. McMillian’s bipolar extremophiles suggested how life took hold and shaped a hostile planet into something more conducive for life. Working for her was a waking dream, for a guy who loved to stay out in any weather.
Professor McMillian’s inflated letter of recommendation—largely accurate, she told me, if still mostly predictive—got me a graduate assistantship at U Dub. Seattle was the best place I could have landed, given my skill set, which consisted of holding still and looking at things, the stranger the better. The microbiology program was strong, and the extremophile people adopted me as close enough for kin.
I joined a multidisciplinary team modeling how oxygenated meltwater between glaciers and the seas kept organisms alive when Earth was frozen up like a giant snowball. According to our models, that sliver of life, over agonizingly long stretches of time, helped turn the snowball planet back into a runaway garden.
While I studied, crazy things were happening far away. Data flowed back from instruments flying all over the Solar System. The planets were wilder than anyone suspected. Moons of Jupiter and Saturn turned out to be hiding liquid oceans beneath their suspiciously smooth crusts. All the Earthly chauvinisms began to fall. We’d been reasoning from a sample of one. Life might not need surface water. It might not need water at all. It might not even need a surface.
I was living through one of the great revolutions in human thought. A few years before, most astronomers thought they’d never live to see the discovery of even a single planet outside the solar system. By the time I was halfway through graduate school, the eight or nine planets known to exist turned into dozens, then hundreds. At first they were mostly gas giants. Then Kepler was launched, and Earth was flooded with worlds, some not much larger than ours.
The universe changed from one semester to the next. People were looking at infinitesimal changes in the light of immensely distant stars—reductions in brightness of a few parts per million—and calculating the invisible bodies that dimmed them in transiting. Minuscule wobbles in the motion of massive suns—changes of less than one meter per second in the velocity of a star—were betraying the size and mass of invisible planets tugging on them. The precision of these measurements defied belief. It was like trying to use a ruler to measure a distance a hundred times smaller than the amount the ruler would expand from the heat of your hand.
We did that. We Earthlings.
New habitats everywhere: no one could keep up. People were finding hot Jupiters and mini-Neptunes, diamond planets and nickel planets, gas dwarfs and ice giants. Super Earths in the habitable zones of K-and M-class stars seemed as suited for a spark of life as this place ever was. The whole idea of the Goldilocks zone got blown wide open. The life we’d found in Earth’s harshest regions could easily thrive in many of the regions now springing up throughout space.
I woke one morning looking down on my body where I lay in bed. I saw myself the way my old mentor Dr. McMillian sized up a new species of archaea. I weighed where I’d come from, my cast of mind, the sum of my failings and capabilities, and I knew what I wanted to do before my small part of this giant experiment ended. I’d visit Enceladus and Europa and Proxima Centauri b, at least via spectroscopy. I’d learn how to read the histories and biographies of their atmospheres. And I’d comb through those distant oceans of air for the slightest signs of anything breathing.