K2-18b orbits a small red star 120 light years beyond our solar system. It is a type of planet that is usually called a mini-Neptune, i.e. a smaller variant of the gaseous Neptune that lies far out in our planetary system.
But unlike other mini-Neptunes, this one is at a distance from its star where water could potentially exist in liquid form.
Flowing water and the presence of carbon-based substances such as carbon dioxide and methane provide conditions similar to those that existed on Earth when life evolved.
Can detect by-products of life
There is still no telescope that can directly find life on alien planets, but it is possible to detect by-products of life, so-called biomarkers. The most prominent biomarker in the Earth’s atmosphere is oxygen produced by green plants and plankton.
On K2-18b, the James Webb telescope has seen indications that there may be another biomarker, namely dimentyl sulfide (DMS), which on Earth can only be produced by life, primarily marine algae. But the evidence is weak and more observations need to be made to be sure it is not measurement error. Furthermore, DMS on an alien planet does not necessarily mean that there is indeed life there.
Differs from the earth
The discovery is accepted for publication in Astrophysical Journal Letters.
– K2-18b is a planet that differs from Earth in many ways. Maybe there is a process that can produce DMS, without life being involved, says Måns Holmberg.
Next spring, the James Webb telescope will make more observations of DMS on K2-18b.
List: Three possible locations for life in space – see more in the video above.