Alien Life on K2-18b: Planet That Emits Gas Produced Only by Life Sparks Interest Among Astronomers

Within our Solar System, Mars is believed to be the other planet that is most likely to harbor life. Rover missions have been sent to the red planet to find evidence of ancient life. However, in a recent study, astronomers are determined to show that extraterrestrial life may also exist on a distant planet.

Super Earth Exoplanet

In 2015, a team of scientists discovered K2-18b, an exoplanet that orbits the red dwarf K2-18 within the habitable zone of its M-type star in the Leo constellation 120 light-years away. Also known as EPIC 201912552 b, it has a radius 2.6 times that of Earth and is 8.6 times more massive. This transiting exoplanet has an orbital duration of 33 days.

This extraterrestrial world is called "super-Earth" because it is more significant than our planet but smaller than Neptune. Its large size means its interior possibly contains a large mantle of high-pressure ice but with a thinner hydrogen-rich atmosphere and an ocean surface. While this type of planet does not exist in our Solar System, sub-Neptunes are the most common exoplanet known in our galaxy.

Life-Supporting Evidence

Last year, experts claimed that they detected dimethyl sulfide gas in the atmosphere of planet K2-18b. To confirm these findings, NASA's James Webb Space Telescope plans to conduct hours of planetary observations on May 3. However, the results must be verified and published several months later.

Dr. Nikku Madhusudhan, an astrophysicist from the University of Cambridge, leads the investigations. He referred to K2-18b as a hyena world, a new term coined for a rocky world that contains oceans of water and a hydrogen-rich atmosphere. If dimethyl sulfide is detected on K2-18b, it puts the planet at the top for potential signs of habitability, Dr Madhusudhan noted.

It was only in 2019 that scientists reported the presence of water vapor in the atmosphere of K2-18b. Last year, it was also discovered to contain methane and carbon dioxide, which caused a shortage of ammonia. Dr. Madhusudhan claimed this to be a profound event because it supports the theory that a water ocean can exist underneath a hydrogen-rich atmosphere.

On Earth, the bulk of dimethyl sulfide is released from phytoplankton in marine environments. This means that its presence in K2-18b suggests a similar life form. Experts cannot think of any natural geological or chemical process that could create dimethyl sulfide without living organisms.

James Webb Space Telescope can analyze the chemical makeup of a distant planet by capturing the light emitted by its host star after it has passed through its atmosphere on its way to Earth. Gases in the atmosphere absorb some of the starlight, although each level leaves signatures in the light spectrum that astronomers can unpick.

Hycean planets are assumed to be covered in water, but astronomers claim that it is also possible that K2-18b's ocean is too hot to be habitable or even exist in liquid form. The study "Distinguishing oceans of water from magma on mini-Neptune K2-18b" suggests that the hypothesized ocean may be lava.