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7:52

There’s a vision of the afterlife that’s incredibly appealing to me. It has nothing to do with reward or punishment and doesn’t even extend beyond the first few minutes at the pearly gates. What I want — desperately — upon transcending the mortal plane is to get answers to all the unanswered questions that plagued me in life.

In this scenario, some people might ask about the fate of the Roanoke colony or the contents of every sealed recommendation letter ever written for them. Who was D.B. Cooper, or how did Stonehenge get built? But I’d want to know: Has there ever been life on other planets?

Not “Are there aliens?” or “Will we make contact via SETI?” or “What really happened in Roswell?” Just has there ever been, anywhere beyond Earth, any kind of life? We got a hair closer to an answer recently, when NASA announced the discovery of some ancient carbon compounds locked in Martian rocks. This isn’t the discovery of life or even its closest chemical cousins. But it’s another step toward hope.

What would be enough for you not to feel alone? I mean, in the cosmic sense. Would it take a definitive SETI signal? A message directed specifically at us? An alien probe or spaceship or (hopefully peaceful) visitation? Would proof of a past alien civilization do it, even if they weren’t still around? Animals without intelligence? Single cells? A ghost of a chemical residue that tells you something was once there?


Before there was life, there was not life. There were rocks and sea and dirt; then there were creatures. There were sugars and amino acids and bubbles and water and oil, and then there was an organized system: life.

Until the 19th century, the idea of life arising from inanimate matter was taken as the status quo. Some living things required parents — humans, dogs, other animals we’d seen giving birth, and plants we’d seen sprouting from seeds — but sometimes, it was thought, spontaneous generation was the rule. When meat sat out too long, maggots started to grow out of it; ergo, maggots spontaneously generated from the meat. A rotting log sprouted mushrooms. Or maybe animals arose from other animals, but not their own kind — a tapeworm birthed by the creature we now understand to be its host.

We learn this story in biology classrooms as proof of how naive and backward humanity once was. But as whimsical as the idea of mice arising from hay may seem now, spontaneous generation must have happened on Earth at least once. There wasn’t life, and then there was. The origin. Abiogenesis — literally, life from not-life.

In those same biology classrooms, we learned a story that has stuck around since the 1950s, that of the “hot, weak soup,” a prebiotic murk shocked by lightning strikes into something more. High schoolers still learn a version of this today, but the science is much weirder and stretches all the way into space.

“How did life begin on Earth?” is a question where science and imagination are one and the same. It’s an utterly unanswerable question, at least barring a time machine and extreme precision. A visit to just the right moment at the right murky shallows, when some twisty molecules in a tiny bubble membrane of clay or oil crossed an undefinable line. Did life begin with metabolism — the ability to thwart entropy and draw energy from the environment? Or was it about coding information, molecules that drive their own replication? Even if you made life in a lab, you could never know how life was actually first made here.

Scientists in this field work with these broad questions and many narrower ones: How might particles of clay knit into a vesicle to give some prebiotic molecules a home? Were those building blocks of life cooked up in our seas, or in the high atmosphere, or out in the depths of interstellar space?

And when we look to other planets, will the story there be the same? When scientists talk about signs of life, they mean signs of life as we know it: They look for water, oxygen, the spectral signature of photosynthesis. But is that a failure of imagination? Is it anthropocentrism or the simple facts of chemistry, of atomic orbits and molecular stability? How different from ours can the building blocks of other life be?

The story of the origin of life on Earth will likely always be a mystery, always a pile of questions. Scientists can work toward understanding how it might have happened, but there’s no way to make an observation to confirm your hypothesis, no way to know how life started here. Forget the n=1 problem of trying to extrapolate from Earth to other planets. This is n=0: trying to understand the prevalence of life in the cosmos without ever being able to know for sure how it started here.

When we look to the cosmos, instead of back through time, there is an answer out there. One way or another. And so we can’t set aside our curiosity, saying, We’ll never know, but it’s a fascinating puzzle! Either there’s life beyond Earth or there isn’t; either intelligent aliens are out there or they’re not. It seems so much simpler, a binary fact, but the mystery of it taunts me, because it’s not just a question—it’s an answer out of reach.


Why does being alone matter? We’ve got enough problems on Earth, enough struggle and beauty to last us generations — if we last that long. Many visions of first contact frame alien visitation as a come-to-Jesus moment for Earth, humanity uniting in the face of a global enemy or recognizing with awe just how small we are.

I hate that view, though, because it presumes that in order for humanity to be united, we still need an external other to measure ourselves against. Even if the aliens are peaceful, they’re still them, the contrast by which we understand a new us.

There are the pipe dreams, too, of super-advanced aliens coming to Earth — or, as in Contact, sending a message — to gift us with near-magical technology. They could solve our problems with a snap of their fingers: clean energy, food replicators, carbon scrubbers for the atmosphere, a new worldview to transcend all conflict. But just like any sufficiently advanced technology would look to us like magic, any sufficiently advanced aliens would look to us like gods. And wishing for their intervention is just wishing to be saved from ourselves, wishing for a snow day so you don’t have to go to school.

The most plausible ways we could discover other life would be through chemical proof in our own solar system or an alien signal from a distant star. Either way, we’re not going to suddenly have new alien friends to talk to. What we find at the Martian poles, or in Europa’s subsurface seas, would never be conversationalists — we’re talking life-forms of a few cells at most. And if SETI finds a signal, the vast distances of space mean that each side of a light-speed conversation will still take likely hundreds of years to transmit.

Here’s what I wish for, within the constraints of plausibility: proof that life once existed on Mars or anywhere else beyond Earth. I don’t need an alien signal or visitation. Just give me a chemical signature, and, preferably, make it weird.

If we find life somewhere else in the solar system, it could be chemically just like ours. This would be an incredibly frustrating discovery, because there’d be no way to know if it somehow shared our origin (think organic matter bashing around the solar system on meteorites) or if our exact biochemistry is the best way to do things, and two chemically identical trees of life independently emerged. Either option would be cool, but there’d be no way to know which was fact.

But life that’s chemically different from ours — in chemical makeup or orientation, a quality called chirality — would be the game-changer. Because we’d know it evolved independently from us. We’d know life had begun more than once. That’s the ballgame. That’s all the hope and possibility, Schrödinger’s cat taken out of its box. (Even if the cat turns out to be nothing more than bacterial sludge.) I think those single-celled organisms make fine compatriots here in the vast cosmos. Even if we can’t talk to them, they’d tell us: We’re not alone.