Trappist-1 b, an Earth-sized planet about 40 lightyears away from us, might have an atmosphere&mdash;albeit a thin, hazy one, rich in carbon dioxide (CO₂)&mdash;according to recent observations by the James Webb Space Telescope (JWST). Newly observed signs of possible geological activity bring into question the previously held belief that the exoplanet&nbsp;in the Aquarius constellation is a barren, rocky world.
Trappist-1 b&nbsp;is part of the Milky Way&rsquo;s Trappist-1 system, which hosts seven rocky planets. Three of these planets are in the so-called habitable zone, where liquid water could exist. However, Trappist-1 b&rsquo;s orbit brings it too close to its star for water to exist there.
New clues&nbsp;
For years, scientists believed that radiation from its red dwarf star and meteors had battered Trappist-1 b&rsquo;s surface, leaving it weathered and stripped of any atmosphere.
However, as scientists analyse thermal infrared data from the JWST&rsquo;s Mid-Infrared Instrument (MIRI), they have found no signs of such extreme weathering. This suggests the possibility of geological activity, such as volcanism or tectonic movement. If the planet&rsquo;s surface is relatively &ldquo;young&rdquo;&mdash;possibly just 1,000 years old&mdash;dramatic processes might be reshaping its crust.
Alternatively, scientists believe Trappist-1 b may have a hazy CO₂-rich atmosphere, which could be trapping heat and altering how the planet emits thermal radiation.
Why is this hard to prove? 
Detecting atmospheres on rocky planets like Trappist-1 b is extremely challenging, even for advanced telescopes like the JWST. Unlike gas giants, rocky planets have thin atmospheres, making their signals faint and difficult to measure. Further complicating things, red dwarf stars&mdash;like Trappist-1, the host star&mdash;emit powerful radiation and winds that can erode atmospheres over billions of years.
In the latest study, scientists used two thermal infrared wavelengths to detect heat from the planet&rsquo;s dayside. They found no dimming caused by a CO₂ layer, which would normally suggest no atmosphere. However, haze could interfere with this reading, heating the upper layers of the atmosphere and masking the results.
What&rsquo;s next?
To solve the mystery, scientists plan to track the planet&rsquo;s entire orbit&mdash;including its transition from the hot dayside to the cooler nightside&mdash;to determine whether an atmosphere is present. If the heat distribution across the planet is smooth, it would suggest an atmosphere is moving heat from one side to the other. On the other hand, a sharp temperature drop between the two sides would confirm the absence of an atmosphere.
Why this matters 
The findings on Trappist-1 b highlight just how complex and challenging it is to study atmospheres on Earth-sized exoplanets. Planets like these produce weak signals,&nbsp;and red dwarf stars add&nbsp;noise to the data, so astronomers must rely on long, painstaking observations.&nbsp;
However, these efforts are worth it. So much so that NASA is dedicating 500 hours of JWST observations&mdash;at an estimated operational value of $85 million&mdash;to studying rocky exoplanets.
For now, Trappist-1 b remains an enigma. However, learning if it has an atmosphere or an active surface could transform our understanding of rocky planets&mdash;and bring us one step closer to discovering habitable worlds beyond our own.

AI representation of Trappist-1 b with its host star in the background

New findings cast doubt on belief that the Earth-sized Trappist-1 b is a rocky, barren world

Atmosphere on an Exo Planet? Science Thinks So!

New findings cast doubt on belief that the Earth-sized Trappist-1 b is a rocky, barren world

December 18, 2024 | 14:48 IST