The rock on Trappist-1 b’s surface seems remarkably young—likely no older than 1,000 years—despite the planet itself being billions of years old.
The mysterious exoplanet Trappist-1 b is once again challenging our understanding of distant worlds. Recent data from the James Webb Space Telescopec (JWST) suggest that this rocky planet, located just 40 light-years away, might be more complex than previously thought. Long believed to be a barren, atmosphere-less rock shaped by relentless radiation and meteorite impacts, new findings hint at the possibility of geological activity—or even a hazy carbon dioxide atmosphere.
Rethinking a Familiar World
Trappist-1 b is part of a unique system of seven rocky planets orbiting an ultracool dwarf star. Three of these planets lie within the “habitable zone,” where conditions might allow liquid water to exist. Astronomers have been fascinated by this planetary lineup, dedicating extensive observation time—over 290 hours across ten JWST research programs—to unlock its secrets.
The latest findings focus on Trappist-1 b’s surface and thermal emissions, captured using JWST’s Mid-Infrared Imager (MIRI). The results, published in Nature Astronomy, contradict earlier assumptions. “The idea of a heavily weathered, atmosphere-less planet doesn’t align with the current measurements,” explained Jeroen Bouwman of the Max Planck Institute for Astronomy (MPIA). “Instead, the surface appears relatively untouched.”
The rock on Trappist-1 b’s surface seems remarkably young—likely no older than 1,000 years—despite the planet itself being billions of years old. This suggests dramatic geological activity, such as extreme volcanism or shifting tectonic plates, akin to processes on Earth or Jupiter’s volcanic moon Io. These phenomena might be fueled by residual heat from the planet’s formation or tidal forces exerted by the central star and neighboring planets.
The Atmosphere Debate: Evidence or Absence?
Adding to the intrigue, researchers speculate that Trappist-1 b might host an atmosphere rich in carbon dioxide. A key clue lies in the potential presence of hydrocarbon haze, similar to the smog on Saturn’s moon Titan. This haze could reverse the typical temperature layering of an atmosphere, warming the upper layers through greenhouse effects and ultraviolet radiation from the host star.
However, the evidence remains inconclusive. Observations targeting the infrared absorption of carbon dioxide didn’t detect significant dimming, suggesting the absence of a thick atmosphere. Even so, the data leave room for alternative interpretations, emphasizing how challenging it is to study thin atmospheres on rocky exoplanets.
New Methods, New Horizons
Astronomers have long relied on transit spectroscopy to analyze exoplanet atmospheres. This method measures the dimming of a star as a planet passes in front of it, revealing atmospheric composition through specific light wavelengths. However, for stars like Trappist-1, which exhibit frequent flares and starspots, this approach is less reliable. Instead, researchers turned to secondary eclipse measurements, observing the heat radiated by the planet’s day side as it moves behind its star. These observations provide critical insights into surface and atmospheric properties but require significantly more observation time.
NASA’s recently approved “Rocky Worlds” program is set to expand on these techniques. Allocating 500 hours of JWST observation time, this initiative aims to investigate the atmospheres of rocky planets orbiting nearby, low-mass stars, with Trappist-1 b as a prime candidate.
What’s Next for Trappist-1 b?
Future observations will offer a clearer picture of Trappist-1 b’s nature. Researchers plan to map its entire orbit, capturing all phases from the dark night side to the illuminated day side. This method, known as phase curve analysis, will reveal how heat is distributed across the planet’s surface. A significant temperature difference between the day and night sides would confirm the absence of an atmosphere, while a smoother heat distribution would suggest otherwise.
For now, Trappist-1 b remains a tantalizing mystery, exemplifying both the promise and complexity of studying exoplanets. As new data emerge, this enigmatic world could rewrite our understanding of planets beyond the solar system.