How astronomers plan to detect the signatures of alien life in the atmospheres of distant planets

We live in a very exciting time: answers to some of the oldest questions humanity has conceived are within our grasp. One of these is whether Earth is the only place that harbours life.

In the last 30 years, the question of whether the Sun is unique in hosting a planetary system has been resoundingly answered: we now know of thousands of exoplanets orbiting other stars.

But can we use telescopes to detect whether any of these distant worlds also harbour life? A promising method...