Between tidepooling sessions I’ve been reading about Proxima b, a newly discovered planet orbiting the star closest to our sun. Good news: this planet in our galactic backyard is just slightly larger than Earth, meaning it is more likely a rocky world similar to our own planet than a gas giant like Jupiter. More good news: Proxima b is in the Goldilocks zone. Not too cold for its water to freeze, not too hot for its water to turn to gas, Proxima b orbits its star at just the right distance for liquid water to pool. On Earth, wherever water pools, life thrives, and tidepools at the ocean’s edge teem with wondrous forms. But tidepooling on Proxima b would be a drastically different experience than exploring the shores of Earth.
Because Proxima b is so close to its red dwarf star, which is much smaller than our Sun, the planet is most likely tidally locked with its star—similar to how our Moon always points the same face toward Earth as it rotates in synchrony with our planet. If Proxima b is indeed tidally locked, one side of the planet forever sears as it faces its star; the other side endures endless darkness and chill. The temperature extremes of the different faces might, however, be moderated by mixing.
Heat energy could be redistributed from Proxima b's hot, star-facing side to its cold, space-facing side through convection, similar to the circulation in a pot of water on a heated stove. This thermal convection could drive powerful ocean currents and winds of torrential force in an atmosphere far different from our own. Liquid water is almost certainly a requirement for life, but its presence on a planet is no guarantee we will find alien beings. Mars and Venus orbit our Sun in the habitable zone, yet their atmospheres are not conducive to life as we know it.
Perhaps the most profound challenge to life getting started and persisting on Proxima b is the nearness of the planet to its star. Proxima b is blasted by radiation much stronger than what we receive from our comparatively distant Sun. Also, Proxima b might not have a satellite as massive as our Moon, which has played a crucial role in evolution on Earth. But in the dice roll of life developing in the cosmos, Proxima b does have one feature that tips the odds in its favor: time.
For life to get started and evolve into complex forms that develop intelligence, time is as essential as water. Proxima b has time in spades, for the planet’s small, dim star burns so slowly it will persist for trillions of years. The expiration date on our comparatively fast-burning Sun is a mere five billion years from now. So, regardless of whether Proxima b harbors life, it could serve as a future home for humanity. But before we start packing our bags for this interstellar move, we would be wise to remember, as astronomer Martin Rees has pointed out, that billions of years from now, the creatures we evolve into could resemble humanity as much as we resemble the microbes that gave rise to us.
Life is a complicated continuum with countless false starts, dead ends, and circuitous routes, a point made clear by perusing fossils in a museum, and by gazing through a microscope at the multitudes of different creatures in a teaspoon of seawater. We could no more imagine the beings we will become when we leave our solar system than sea slugs could envision their distant cousins on the tree of life radiating into giraffes and pandas and people. That is not to say we should be tentative about taking our first steps into the vast cosmic ocean. On the contrary, we should boldly leap.
The sooner we can get our feet wet in the shores beyond our solar system, the better, for a more immediate threat than the death of our star looms over our species. Because nuclear energy has been harnessed by humans, and megatons of destructive energy can now be released in mere seconds, whether by a computer glitch or by a psychotic tyrant, it is imperative that we move as fast as possible toward establishing outposts on other worlds.
Of course, once our species establishes itself beyond Earth, new crises of our own making will threaten our survival, for the seeds of our destruction are carried in the aggression and tribalism coded in our genes. Editing our genome to maximize intelligence and compassion through new biotechnology advances like CRISPR is one potential technique in our toolkit of survival, along with colonizing multiple worlds that orbit distant suns.
Practical visionaries on Earth have a plan to send probes to our nearest stellar neighbor in the not-too-distant future. By midcentury, scientists could be crunching data about alien geology and atmosphere, and perhaps even examining signatures of life beamed back by missions to Proxima b.
What creatures might live on the twilit margins of Proxima b, where the planet’s star-warmed oceans merge with the cold seas of the dark side? It seems unlikely to me that life could survive, much less thrive, in such bizarre conditions. But then I read of organisms at the bottoms of our oceans that are powered not by sunlight but by chemicals belched from deep-sea vents—a discovery made in the 1970s. And I remember that when I was a boy cracking open my first biology textbook, scientists scoffed at the thought of life thriving in scalding hot springs, or organisms living deep in the rock crust of our planet, or microbial lifeforms lofted into the atmosphere miles above Earth’s surface. If there is life on Proxima b, it most likely occurs in forms that stretch our capacity to imagine them.
One possible signature of life on planets bombarded by solar flares is fluorescence—and we might observe this glow through telescopes. Some scientists think organisms on Proxima b could survive solar storms by transforming harmful radiation into glowing light. Strange sea creatures on Earth feed this speculation. Corals absorb short-wave, high-energy UV light and turn it into longer, less energetic waves. This process is thought to shield corals and the algae they host from harmful radiation.
Glowing corals create a dazzling visual experience for divers. These fluorescing animals also stimulate the imagination of researchers trying to comprehend the kinds of life we might encounter on a cosmic journey.
The intuitive bridge that scientists are building from glowing sea creatures to life on a planet blasted by solar radiation is as remarkable as sending a probe to Proxima b. The scientific method is clearly our best tool for making sense of the universe, but without curiosity and imagination, we would never venture into new frontiers. So many of our species' collective dreams, from Poseidon of Greek mythology to the white whale of Moby Dick, have risen from the life-stirred depths of the sea. If we continue to exterminate life in the oceans, our capacity for wonder could be one of many casualties.
Last night, while climbing a headland as the setting sun spilled red light across the Pacific, my mind conjured a scene on Proxima b. As I made my way onto a rock prow jutting into the radiant dusk, I imagined Proxima b’s red dwarf sun casting a crimson glow across the star-ward side of the planet. What kinds of life could we find in the seas beneath the eerie skies of Proxima b? What creatures, microbial or massive, might inhabit the eternal night of its dark side? Single-celled plankton carried by surging currents? Whale-like beasts that seine the churning seas? Gossamer serpents that ride colossal winds and fluoresce in solar storms?And what strange beings inhabit the thousands of other planets we’ve recently discovered outside our solar system? And closer to home, what unfathomable forms will we discover as we explore the 95 percent of the world’s oceans unseen by human eyes?
Life on this planet still has plenty of surprises in store for us. As we continue to probe biological mysteries in our oceans, the discoveries we make will help us better understand life’s potential on a nearby planet orbiting a red star, and on worlds stranger yet.