Context: Recently, an international research paper reported that the distant exoplanet K2-18b may be habitable. Potential biomarkers were identified based on the observations from James Webb Space Telescope, backed by computer-based spectral analysis.
Relevance of the Topic:Prelims: Key facts about K2-18b.
What is K2-18b?
- K2-18b is an exoplanet — a planet outside the solar system. It is located 124 light years away from the earth in the constellation Leo, orbiting the star K2-18.
- It is over 5 times wider and roughly 9 times more massive than the Earth.
- The amount of stellar radiation it receives from its star is comparable to what the Earth receives from the Sun. It likely possesses a hydrogen-rich atmosphere.
- It was discovered by the Kepler telescope in 2015.
Earlier estimations of planetary conditions in K2-18b:
- In 2019, the Hubble Space Telescope found that its atmosphere contains signs of water vapour. Later, the James Webb Space Telescope detected signs of carbon dioxide and methane.
- Studies suggest, K2-18b might be a Hycean world: covered with an ocean overlaid by a hydrogen-rich atmosphere.
- Researchers suggest its surface conditions may be close to the runaway greenhouse threshold — when the concentration of greenhouse gases in the atmosphere prevents any heat from escaping the surface.
- Computer models suggest it may also have a stratosphere and some carbon oxides and cyanide in the middle atmosphere.
Recent findings that suggest K2-18b might be habitable:
- The latest research reported the presence of at least one of two molecules that are associated with life: dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) in K2-18b’s atmosphere.
- DMS could be a biomarker (a sign of life) on exoplanets. On Earth, these gases are produced by marine phytoplankton and bacteria.
- Phytoplankton produce a molecule called dimethylsulphoniopropionate (DMSP). When they die, enzymatic breakdown of DMSP molecules releases DMS.
- DMS is also emitted when bacteria break up plant matter. In 2015, researchers reported that 76% of soil bacteria contain a gene that allows them to produce DMS.
- Volcanic eruptions also release trace amounts of DMS.
However, attempts to look for conditions suitable for life and the presence of specific molecules from a distance can only be suggestive of habitable conditions, not confirmatory. The only way to find extraterrestrial life is to directly detect it.
NASA has launched its Clipper Mission in 2024 to study Jupiter’s moon Europa, which among other objectives aims to track signs of life in its vapour plumes.