Scientists Use Webb to Detect Carbon Dioxide and Methane in Exoplanet within the Habitable Zone

Scientists have made a groundbreaking discovery using the James Webb Space Telescope, revealing the presence of carbon-bearing molecules in the atmosphere of exoplanet K2-18 b. This finding has provided valuable insights into the nature of this intriguing exoplanet, which is believed to be a Hycean planet, potentially featuring a hydrogen-rich atmosphere and a water-covered surface.

K2-18 b orbits within the habitable zone of its parent star, a region where conditions are conducive to the existence of liquid water. Initial data from NASA’s Hubble Space Telescope hinted at the unique properties of the exoplanet’s atmosphere, sparking further research by multiple teams.

Situated approximately 120 light-years away from Earth, K2-18 b is roughly 8.6 times the size of our planet. These types of exoplanets, known as sub-Neptunes, have not been extensively studied since they do not exist within our own solar system. Gas giant planets like Jupiter and Saturn have been the primary focus of planetary research thus far.

The team of scientists involved in this discovery believes that sub-Neptunes are the most common type of planet in our galaxy. By obtaining the most detailed spectrum of a habitable-zone sub-Neptune to date, they were able to identify the carbon-bearing molecules present in K2-18 b’s atmosphere. This knowledge contributes to a better understanding of these types of planets and their potential for harboring life.

The search for life on exoplanets traditionally centered around smaller rocky planets. However, the larger Hycean worlds, such as K2-18 b, offer more favorable conditions for atmospheric observations. This emphasizes the importance of considering diverse habitable environments in the quest for extraterrestrial life.

Webb’s data on K2-18 b revealed high levels of methane and carbon dioxide in the exoplanet’s atmosphere. Interestingly, there was a notable absence of ammonia, supporting the hypothesis that K2-18 b may possess a water ocean beneath its hydrogen-rich atmosphere. Additionally, the observations hinted at the presence of dimethyl sulfide (DMS), a molecule typically associated with life on Earth. Further research is needed to confirm the existence of DMS in K2-18 b’s atmosphere.

Despite the favorable conditions for life on K2-18 b, certain characteristics of the planet may hinder its ability to sustain life. Its immense size, approximately 8.6 times that of Earth, suggests the presence of a highly pressured ice mantle in its interior, resembling the structure of Neptune. The planet’s ocean might also be too warm or too hot to support life.

Obtaining the spectrum data on K2-18 b’s atmosphere presented several challenges. The brightness of the exoplanet’s parent star interfered with Webb’s observations. To overcome this, Webb observed K2-18 b as it transited in front of its star, recording a dip in brightness and collecting data on the exoplanet’s atmosphere when illuminated by the star. This method is commonly employed by scientists researching exoplanets and has also been instrumental in discovering new exoplanets.

The team was able to extract atmospheric data from just two transits of K2-18 b, showcasing the power and capabilities of Webb in exoplanet science. Additional observations are scheduled in the coming weeks, using Webb’s Mid-Infrared Instrument spectrograph, to gather more data and potentially identify additional molecules.

The ultimate goal of scientists is to identify life on a habitable exoplanet, which would revolutionize our understanding of our place in the universe. This discovery marks a promising step towards a deeper understanding of Hycean worlds and their potential for supporting life.

The results of this study have been published in The Astrophysical Journal Letters journal, marking a significant contribution to the field of exoplanet research. With the launch of the James Webb Space Telescope, scientists are poised to uncover more secrets of the universe and potentially answer the age-old question: Are we alone?