Alien Worlds Might Be Covered in Enormous Mountains

On the sublime scenery that might await us on exoplanets.

The Maroon Bells.  (Ross Andersen)

Fourteen miles outside Aspen, as the rental car flies, there are two hump-backed mountains measuring more than 14,000 feet each. They can be seen from a small neighboring valley, from the shores of a shallow lake, whose smooth waters carry an inverted image of the snow-striped peaks. Called the Maroon Bells, for the way they light up red at dawn, the pair are said to be the most-photographed in Colorado, a state with no shortage of sublime scenery.

Yesterday, I made the pilgrimage to see the Maroon Bells with Lisa Kaltenegger, a professor of astronomy at Cornell. Earlier in the day Kaltenegger had appeared on a number of panel discussions co-hosted by the Aspen Institute and The Atlantic. The Director of Cornell’s Carl Sagan Institute, Kaltenegger spent most of her stage time talking about planets in distant star systems, and the possibility that some of them play host to life. Kaltenegger is accustomed to making this pitch. Her institute was founded to research “biosignatures,” telltale signs of life that can be seen through telescopes, from tens of trillions of miles away. (An abundance of oxygen and methane could, for instance, indicate the presence of living, breathing organisms.) Like many astronomers, she is hopeful that such signatures will be glimpsed around nearby stars within the next decade.

As we stood admiring the Maroon Bells, I asked Kaltenegger whether she thought there were scenes like this all across the cosmos. “No,” she said, before explaining that Earth was but a single, limited expression of nature’s raw creative power. Just as our planet contains many habitats with many ecologies, each with its own diverse creatures, other planets may play host to living worlds that look nothing like our own.

“Take mountains,” she said. “Earth’s crust is quite thin, which means its mountains can only reach so high.” This seemed ungrateful, surrounded as we were by jagged, vertical rock faces, studded with dense pine stands. “If Earth’s crust were thicker, the mountains could be much larger,” she said.

On some distant planet, there might be peaks that tower more than 100,000 feet above an alien sea. These extraterrestrial peaks might be forested, or they might be coated in an alien form of vegetation, or something beyond the reach of our current imagination.

We left the Maroon Bells shortly after the sun dipped behind a neighboring peak, taking the warmth with it. I returned to town, and set up shop on a back deck with a with a wide view of the sky. Only a week past the solstice, it was still blue, even at 9 o’clock. In the southern sky, Mars was shining, its light unmistakably orange. On its surface, our probes have spotted a mountain that measures more than 88,000 feet, from base to peak.

Over a period of an hour, the sky  turned purple, and then a deep shade of black. Mars was joined by one star, then two, then a whole host, all massed together, in the smear of light that we call the Milky Way. Billions of rocky planets twirled around them. Some of them are covered in peaks that would likely make molehills of the highest Martian mountains, to say nothing of Everest and, yes, the Maroon Bells. But until we find life on one, we can continue to tell ourselves that Earth’s peaks are the fairest, tiny though they may be.