K2-18b

K2-18b is an exoplanet discovered in 2015 by NASA’s Kepler Space Telescope and holds significant importance in the study of planets outside the Solar System that may harbor life. K2-18b has attracted scientific attention as a planet thought to potentially support Earth-like conditions, particularly due to the detection of methane and carbon dioxide in its atmosphere.

Discovery and Characteristics of K2-18b

K2-18b was discovered during the Kepler Space Telescope’s K2 mission and is located approximately 124 light-years from Earth. It orbits the star K2-18, which is similar to the Sun, and resides within the star’s habitable zone. While definitive information about the planet’s surface and atmosphere remains unavailable, scientists believe K2-18b is a super-Earth and may possess surface conditions capable of supporting liquid water.

K2-18b Planet (BBC)

James Webb Telescope and New Discoveries

In April 2025, observations made by the James Webb Space Telescope revealed the presence of methane and carbon dioxide in the atmosphere of K2-18b. This discovery provides a significant clue that biosignatures may exist on the planet. Scientists suggest that gases such as methane and carbon dioxide could be produced by biological processes. This finding underscores the importance of K2-18b in the search for potential life.

Biosignatures and the Probability of Life

The detection of methane and carbon dioxide in K2-18b’s atmosphere presents a compelling possibility of biosignatures for scientists evaluating the planet’s potential to support life. On Earth, methane is predominantly generated by biological sources, while carbon dioxide can be a byproduct of biological processes such as photosynthesis. The presence of these gases strengthens the hypothesis that traces of life may exist on the planet and that its environment could be conducive to life. However, methane and carbon dioxide can also originate from geological processes, not exclusively biological ones. Therefore, further observations are required before any definitive conclusions can be drawn.

Atmospheric Composition of K2-18b (NASA)

Water and Possibilities for Life

Research into K2-18b’s potential to support life has increased the likelihood that liquid water exists in its atmosphere. According to recent NASA studies, the surface of K2-18b may possess conditions favorable to the presence of liquid water. Experts propose that the planet’s water vapor, atmospheric gases, and temperature conditions could together create an environment suitable for life. However, it has not yet been confirmed whether liquid water exists on the planet’s surface, and further investigation is necessary to resolve this question.