... stars . ... Finding twin Earths is harder than we thought . Astronomers need a handful of transits to decipher a planet's atmosphere and possibly confirm the existence of the first twin Earth. ... If an earthlike world is nearby, though, then by adding observations of a number of transits, astronomers should be able to detect biomarkers like methane or ozone. ... They are also cooler and dimmer than the Sun, as well as smaller, which makes finding an earthlike planet transiting an M star easier. ...