A new study led by the Southwest Research Institute (SwRI) has decoded the puzzling atmosphere of TOI-270 d, a distant exoplanet located just 73 light-years from Earth, revealing it to be a super-Earth shrouded in a thick, searing-hot atmosphere. Using data from NASA’s James Webb Space Telescope (JWST), researchers now believe this planet could be the key to understanding an entire class of exotic worlds—earning it the nickname “Rosetta Stone” exoplanet. The findings are published in a new paper accepted by The Astrophysical Journal and available on arXiv.
The Mysterious World of TOI-270 d
TOI-270 d belongs to a category known as sub-Neptunes, planets that are larger than Earth but smaller than Neptune. These planets are among the most common in the galaxy, yet they don’t exist in our own solar system—making them one of the most intriguing targets in exoplanetary research. While some scientists hypothesized that TOI-270 d might be a Hycean world—a water-covered planet with a hydrogen-rich atmosphere—recent JWST data paints a very different picture.
Researchers now suggest that TOI-270 d is likely a rocky world with a molten surface, overlaid by a superheated atmosphere where temperatures exceed 1,000°F, making it hotter than Venus. This extreme environment, according to study lead Dr. Christopher Glein, presents an unparalleled opportunity to explore planetary evolution in conditions vastly different from Earth. “I was shocked by the level of detail they extracted from such a small exoplanet’s atmosphere, which provides an incredible opportunity to learn the story of a totally alien planet,” he noted. With molecules like carbon dioxide, methane, and water detected, Glein believes scientists can begin using geochemistry to investigate how such unusual worlds form.
Why No Ammonia? A Missing Piece Explained
One of the biggest surprises in the data was the absence of ammonia, a compound long expected to be present in hydrogen-rich atmospheres like this one. The team’s model suggests that extreme surface temperatures and magma ocean chemistry are likely destroying or absorbing the ammonia before it can rise to detectable levels. Instead, the atmosphere may be dominated by nitrogen gas, formed through high-temperature processes.
Glein emphasized the broader implications of these findings: “While it is a bit disappointing to find that TOI-270 d is unlikely to be habitable, this planet still offers a fantastic opportunity to explore alternative paths of planetary origins and evolution,” he said. “We are learning much more about the crazy configurations of planets that nature comes up with.”
This new approach blends geochemistry with atmospheric modeling to explain not just what’s in the air—but how it got there. The planet’s lack of nitrogen-rich material may also stem from its early formation, using building blocks that, like many chondritic meteorites, are inherently nitrogen-poor.
Rewriting the Rulebook for Exoplanet Science
These revelations show that JWST’s capabilities go far beyond simply spotting planets—they enable deep chemical analysis of alien atmospheres, offering insights once thought limited to our own solar system. “The JWST data on TOI-270 d collected by Bjorn Benneke and his team are revolutionary,” said Glein, highlighting the unprecedented resolution achieved for a planet of this size.
The research also challenges previous models that assumed sub-Neptunes could be early candidates for habitability. Instead, TOI-270 d’s high temperatures and volatile chemistry suggest a hostile world, but one rich in scientific value. Glein likened the diversity of planetary configurations to evolutionary biology: “A core set of building blocks and rules for interactions result in an explosion of diverse forms.”
What TOI-270 d Tells Us About Planetary Evolution
As the catalog of known exoplanets passes 5,800, TOI-270 d offers a critical case study for how rocky planets evolve under extreme conditions. With JWST and future telescopes like LUVOIR and Habitable Worlds Observatory, scientists hope to apply these geochemical tools to even more targets.
“This is just one planet,” Glein reflected. “It’s going to be very interesting to see what the next exoplanet has in store for us.”
Source: The Daily Galaxy / Digpu NewsTex