On Friday 26th June 2015 at 7pm, Professor Monica Grady of the Planetary and Space Science Department at the Open University gave the Royal Irish Academy McCrea Lecture 2015. She was part of the Rosetta science team at mission control when the landing of the Philae space probe occurred. In her talk she introduced the topic of comets and explained why some people think they may have led to life on Earth and possibly its destruction through mass extinctions. She give a highly entertaining personal account of the Rosetta Mission, her involvement in it, and reported on some of its latest results. She finished by the 140 attendees that the mission still had over a year to go, and that many more scientific discoveries would be announced in the coming months.