Space: Do aliens really exist?
In the final instalment of Newsround's space week, Joe's asking the biggest question of all about our universe. Do aliens exist?
Space agencies around the world have spent the last 80 years exploring space and trying to find life on other planets.
Joe's been speaking to top astronomers to get the answers.
Are we alone on planet earth or could there really be life out there?
Watch his film to find out...More from Space Week: