Are we now closer to finding life on another planet? - What in the World podcast, BBC World Service

Key Concepts

• Exoplanet: A planet that orbits a star outside of our solar system.
• Habitable Zone: The region around a star where the temperature is just right for liquid water to exist on a planet's surface.
• Atmosphere: The layer of gases surrounding a planet.
• Nitrogen-dominated atmosphere: An atmosphere where nitrogen is the most abundant gas, similar to Earth's.
• Infrared light: Electromagnetic radiation with longer wavelengths than visible light, often associated with heat.
• Tidally locked: A celestial body that rotates at the same rate that it orbits, resulting in one side always facing the primary body.
• James Webb Space Telescope (JWST): A powerful space telescope launched in 2021, designed to observe the universe in infrared light.

Discovery of TRAPPIST-1e and Potential for Life

Scientists are currently very excited about the exoplanet TRAPPIST-1e, which is considered a significant step in the search for extraterrestrial life.

• Planet Characteristics: TRAPPIST-1e is a rocky planet, similar in size to Earth, and orbits within the habitable zone of its star, TRAPPIST-1. Being in the habitable zone means that if water is present, it is likely to be in liquid form, a key ingredient for life as we know it.
• Atmospheric Clues: Initial observations suggest that TRAPPIST-1e's atmosphere is not dominated by hydrogen or carbon dioxide, which would make the planet too hot due to their greenhouse effect. Instead, there are indications of a nitrogen-dominated atmosphere. Nitrogen is the primary gas in Earth's atmosphere (approximately 78%) and is considered a positive sign for the potential of life.
• Significance of Nitrogen Detection: The potential detection of nitrogen in TRAPPIST-1e's atmosphere is groundbreaking. While not definitive proof of life, it is the first time scientists have identified this crucial gas on an exoplanet, bringing humanity closer than ever to finding alien life.

The Role of the James Webb Space Telescope

The James Webb Space Telescope (JWST) has been instrumental in these recent discoveries.

• Unprecedented Power: The JWST is described as incredibly powerful, with one scientist noting its ability to detect the heat of a bumblebee on the moon. It is estimated to be 100 times more powerful than the Hubble Space Telescope.
• Infrared Observation: Unlike telescopes that focus on visible light, the JWST specializes in observing infrared light. This is advantageous because infrared light is emitted by smaller, colder bodies and can travel further through space, allowing for the detection of distant stars and planets.
• Telescope Design: The JWST features a massive mirror, six and a half meters across, which is two and a half times larger than Hubble's.
• Methodology for Atmospheric Analysis: The JWST detects atmospheric composition by observing how the planet's atmosphere alters the infrared light from its star as the planet passes in front of it. Specific gases in the atmosphere cause subtle changes in this light, which the telescope can then analyze.

Future Research and Challenges

Further study of TRAPPIST-1e is planned to confirm the presence and composition of its atmosphere.

• Continued Observation: Scientists have observed TRAPPIST-1e passing in front of its star four times and plan to conduct an additional 15 observations. Results are expected next year.
• Confirmation of Nitrogen: These future observations aim to confirm whether the planet indeed has a nitrogen-rich atmosphere.
• Further Atmospheric Analysis: If nitrogen is confirmed, the next step will be to identify other gases present and use models to determine the planet's temperature and its suitability for supporting life.
• Distance and Travel: TRAPPIST-1e is approximately 40 light-years away. Current spacecraft technology would take about a million years to reach it, making interstellar travel to this planet unrealistic for humans in the foreseeable future. Mars is suggested as a more feasible near-term target for potential human colonization.
• Tidal Locking: A significant challenge for potential habitability on TRAPPIST-1e is that it is tidally locked. This means one side of the planet perpetually faces its star, experiencing constant daylight, while the other side is in perpetual darkness.

Perspectives on Alien Life

The discovery has sparked discussions about the nature of potential alien life and human reactions to it.

• Young Explorers' Views: Ximena and Vanessa, members of the Cosmic Girls Foundation, expressed excitement about the discovery. Ximena was particularly drawn to the Earth-like characteristics of the planet, while Vanessa, a biology enthusiast, found the possibility of life elsewhere fascinating.
• Fear vs. Curiosity: When asked about the prospect of finding alien life, Vanessa expressed more curiosity than fear, hoping that aliens would be as curious about us as we are about them. She believes knowing we are not alone would be a wonderful realization.
• Nature of Alien Life: Caroline Steele noted that the appearance of extraterrestrial life is unknown. It could range from simple microbes to highly intelligent beings, potentially more advanced than humans. Distinguishing between different forms of life from Earth using telescopes will be challenging due to the vast distances involved.
• Past Exaggerations: The discussion touched upon past instances where early claims of exoplanet habitability, like with Gliese 581g in 2010, were later found to be inaccurate or exaggerated, leading to increased caution among scientists and journalists.

Conclusion

The discovery of potential atmospheric signs on exoplanet TRAPPIST-1e, particularly the possible presence of nitrogen, represents a significant advancement in the search for extraterrestrial life. While definitive proof of life remains elusive, the capabilities of the James Webb Space Telescope are providing unprecedented insights into distant worlds. The ongoing research and the perspectives of young aspiring space explorers highlight the enduring human fascination with the cosmos and the profound implications of discovering life beyond Earth.