The Most Hellish Planet Yet
In a place where it rains rocks, we can exclude life for sure, right?
A new study led by Giang Nguyen from York University in Toronto modeled the atmosphere of an exoplanet known as K2-141b—just over 200 light years from us in the constellation Aquarius—and found that this world is truly the most hellish place we can imagine. A massive rocky lava planet, it orbits extremely close to its host star, which is classified as an orange main sequence, or K star.
In general, K stars are suitable for hosting life-bearing worlds, and some are even thought to have “superhabitable” worlds in orbit around them. K2-141b is quite the opposite. With an estimated mass about five times that of Earth, it orbits its star more than 100 times closer than Earth orbits the Sun, making its year less than seven hours long! Temperatures near the surface are so high that the planet likely has a magma ocean tens of kilometers deep.
Nguyen’s simulations suggest a truly bizarre and infernal world. The planet’s interior consists of rocks, as we might expect. But the ocean also consists of rocks. And the atmosphere? Rocks.
How is that even possible? The planet is most likely tidally locked, meaning one side is continually exposed to light and radiation from the star, while the other side is dark. Vaporized rocks and sodium atoms are transported at supersonic speed from the lighted side (where temperatures reach up to 3,000 degrees Kelvin) to the frigid dark side, where they rain down. The authors postulate that a return flow of mass occurs via the magma oceans—a weird twist on Earth’s water cycle. But this process would likely not reach an equilibrium, meaning that the planet’s surface would evolve over time.
This is about as close to hell as we can imagine. So there’s no chance of life on K2-141b, right? At least not life as we know it?
Gerald Feinberg and Bob Shapiro might want to differ. In their classic book Life Beyond Earth: The Intelligent Earthling's Guide to Life in the Universe they suggest the possible existence of “lavobes” and “magmobes” on these kind of worlds. These organisms would live in lava flows and would use the chemical complexity of melted silicate rocks to exploit thermal gradients or chemical sources that provide the energy for life.
I was intrigued by the idea when I first read it, and still am, but I don’t think it’s likely. There are biochemical arguments against it, and there’s an even bigger problem. Earth also has lots of lava flows and huge volumes of magma beneath its surface, even more so in the past than today. Yet no one has ever discovered fossils in granites or basalts, the most common rocks formed when lava or magma cool down and becomes solid. So I don’t expect there’s life on K2-141b. But it’s a hell of a good illustration of how different planets in our own galaxy can be.