It’s a great scientific opportunity of modern times, but we won’t get there with our current observatories.
One of the holy grails of modern science is to find a world, beyond Earth, with life on it.
Perhaps the most exciting possibility is to discover a rocky exoplanet with liquid water on its surface and biosignatures in its atmosphere.
Over the past few decades, astronomers have uncovered thousands of new exoplanets.
Some of them are rocky; some are temperate; some have water.
However, the idea that exoplanet K2–18b is rocky, Earth-like, and has liquid water is absurd, despite recent headlines.
Light filters through K2–18b’s atmosphere when it passes in front of its star, enabling us to measure what’s absorbed.
Based on those absorption lines, the presence of many chemicals can be inferred, including water.
K2–18b is, truly, the first known habitable-zone exoplanet to contain water.
However, it is not rocky; its mass and radius are too large, necessitating a large gas envelope around it.
If its atmosphere were like Earth’s, it would be undetectable by current instruments.
It’s a mini-Neptune: interesting, but not the habitable exoplanet we’re seeking.
For that, we need new, larger, more sophisticated observatories.
Unless we build them, we’ll never find the Earth-like worlds we dream about.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.Ethan Siegel is the author of Beyond the Galaxy and Treknology. You can pre-order his third book, currently in development: the Encyclopaedia Cosmologica.