The habitability of alien worlds is one of the fundamental questions that has not yet been answered. More than 5,000 exoplanets have been discovered that science knows little about and are about to disappear. For example, until now there has been no reliable evidence for the existence of atmospheres on rocky Earth-like worlds. If gas giant exoplanets shamelessly flaunt their swollen atmospheres, then everything about rocky worlds was very vague.

The capabilities of the space observatory named after James Webb were opened to collect data from the atmospheres of exoplanets. This is a rather narrow channel for obtaining invaluable information, but it exists and scientists are actively using it. If the exoplanet is hot enough or passing through the face of its star, Webb captures emission and absorption spectra at the observation site, helping to infer the presence of an atmospheric envelope and its approximate composition.

In 2004, 41 light-years from Earth, in the binary system 55 Cancer on the sun-like star 55 Cancer A, scientists discovered a hot super-Earth 55 Cancri e (55 Cancer e). The exoplanet was about twice the size of Earth and slightly denser than Earth. Since then, 55 Cancer e has been under the close control of many scientific groups, but it has never been possible to detect the presence of atmospheres on exoplanets.

It must be said that planet 55 Cancer e was too hot for life to originate there. It orbits its star at a distance of one-fourth the distance from the Sun to Mercury. After all, its surface is a raging magma ocean. For scientists, this is an opportunity to look into the past of Earth, Venus or Mars, when the planets in our system were also red-hot balls. This is an opportunity to understand the formation processes of atmospheres on rocky planets and their interactions with planetary matter.

Observations of exoplanet 55 Raku e have revealed signs of a dense and thin atmospheric shell. According to the researchers, this is the best evidence for the existence of atmospheres on rocky exoplanets in the entire history of observations of such objects. The data was obtained thanks to the high sensitivity of the “Webb” in the near and mid-infrared range.

Small light fluctuations in the range of 4 to 12 μm are clearly oscillated in the atmosphere of 55 Cancer e and supported (most importantly in this study) by the global magmatic ocean. In other words, the rocky world independently creates and supports the atmospheric crust. The primitive atmosphere would have been destroyed long ago by the radiation of a nearby star.

Webb also determined that the dayside of the exoplanet was colder than simulations predicted. Measurements showed that the surface temperature on the dayside was 1540 °C. If the planet had no atmosphere, its temperature would rise to 2000 °C. Cooling can be caused by the movement of lava flows or atmospheric masses from the day side to the night side (the planet, i.e. the ship, is tidally influenced and one side is always facing its star). The bench can be excluded – clearly not the same dynamic. Thus, another indirect evidence of the existence of an atmosphere on 55 Rakue was obtained.

“Ultimately, we want to understand what conditions allow a rocky planet to support a gas-rich atmosphere: a key component of a habitable planet.” – say researchers.