As part of Newsround's space week, Joe's been looking at Mars and why humans are so interested in the planet.
Out of all the planets in our solar system, other than Earth, it's the one that gets all the attention.
In August NASA's Curiosity rover landed on its surface with a mission to search for evidence of life on the planet.
And scientists believe Mars is the only other planet that humans could realistically live on in the future.
Joe's been finding out why...