Why are scientists so optimistic? The Kepler space telescope gets much of the credit. Before it was launched into orbit in 2009, astronomers couldn't be sure whether planets existed outside our solar system. The search for extraterrestrial life was mostly focused on our own solar system — on Mars and a number of moons around Jupiter and Saturn — and on an intergalactic eavesdropping project known as SETI (the Search for Extraterrestrial Intelligence).