13 March 2016 Last updated at 12:18 GMT
The craft, part of the European-Russian ExoMars programme, lifted off from the Baikonur spaceport in Kazakhstan on board a Proton rocket at 9.31am (UK time), starting a seven-month journey through space.
It is carrying equipment to study gases around Mars, such as methane, which is a chemical that is strongly linked with life on Earth.
This is the first of two ExoMars missions, together costing Â£924 million, designed to uncover signs of past or present life on the Red Planet.
Watch Leah's report to find out more.
A spacecraft set off for Mars on Monday on a mission that scientists hope will help answer one of the most burning questions of space exploration - is there life on other planets?