托福听力

🎧 听力原文

Listen to part of a lecture in an astronomy class. The professor is discussing the possibility of life on exoplanets. Professor: When we talk about finding life beyond Earth, we usually focus on the so-called 'habitable zone' around a star—the distance where liquid water could exist. But that's just a starting point. For example, some moons of Jupiter and Saturn, like Europa and Enceladus, have subsurface oceans beneath thick ice layers. These oceans are kept liquid by tidal heating, not by sunlight. So, in exoplanet research, we're also considering moons around giant planets, which might be more common than we thought. However, there are challenges. A moon needs to be large enough to retain an atmosphere, and its orbit must be stable over billions of years. Also, the parent planet's magnetic field could create intense radiation, stripping away atmospheres. So, while the idea is exciting, we still need better telescopes to detect such moons. For now, we're developing models to predict what signs of life, like certain gases, might look like in their atmospheres.