On a sweltering world just 41 light-years away, where a year lasts less than 17 hours and the surface glows red with molten rock, NASA’s James Webb Space Telescope has detected something unexpected: a hydrogen-rich atmosphere clinging to the super-Earth 55 Cancri e. This discovery, led by astronomer Ignas Snellen and his team, upends long-standing models that predicted lava planets like this one would be shrouded in carbon-heavy air. Instead, Webb’s observations of five separate eclipses reveal a dynamic, chemically reduced atmosphere dominated by carbon monoxide and laced with hydrogen—clues pointing to a magma ocean starved of oxygen deep beneath the surface.
Why does this matter? Because atmospheres of rocky exoplanets aren’t just surface features—they’re windows into planetary hearts. The composition of gases escaping from 55 Cnc e suggests its interior has a low oxygen fugacity, meaning it formed under highly reduced conditions where hydrogen and iron dominate over oxygen. This chemical fingerprint, captured in the data published on arXiv and pending peer review in Nature Astronomy, offers the first direct insight into how lava worlds outgas and evolve, linking their scorching skies to the churning magma below.
With a radius 1.88 times and a mass roughly 8 times that of Earth, 55 Cnc e orbits so close to its sunlike star that its dayside likely reaches temperatures exceeding 2,000°C—enough to melt silicate rock into vast seas of lava. Tidally locked, one side bakes in perpetual daylight while the other remains in darkness. But what surprised researchers most wasn’t just the presence of hydrogen, but the variability between eclipses—fluctuations hinting at transient clouds or episodic outgassing, possibly as vaporized rock condenses and is then blasted away by fresh eruptions.
Among known lava planets—like K2-141 b, TOI-561 b, and CoRoT-7 b—55 Cnc e stands out not only for its proximity to Earth but for the clarity with which Webb has revealed its atmospheric chemistry. Unlike Jupiter’s moon Io, where tidal forces drive volcanism, 55 Cnc e’s fury comes from stellar proximity, making it a prime analog for understanding how extreme heat reshapes rocky worlds.
As we peer deeper into the atmospheres of distant super-Earths, each observation brings us closer to decoding the hidden interiors of planets beyond our solar system. With Webb’s precision, even the most infernal worlds are beginning to share their secrets.