4  Prospects for extraterrestrial life

As mentioned in Week 6, we still don’t really know how likely it is for life to spontaneously evolve on a planet, even if conditions are apparently favourable. The only way that we can really make an informed estimate is to look for evidence of life on another planet. This evidence may be present in transmission spectra. So, if a potentially habitable planet transits its star, like the planets in the TRAPPIST system, then we may be able to detect signs of life.