Scientists at Nasa say that a ship they blasted into space 10 months ago is expected to reach Mars on Sunday.
Watch the Nasa video of the mission:
The Maven ship - which stands for Mars Atmosphere and Volatile Evolution spacecraft - will look at how the red planet intersects with the sun and solar winds.
But the mission is complicated because the planet moves at a different speed to earth.
The vessel has to fired from behind its orbit so that it catches up to Mars like trying to aim at a 'moving target'.
It means that Nasa could not fire the ship straight at the planet, because Mars moves around the sun at almost 13,000 mph, significantly slower than the earth.
On November 13 last year the Maven ship was launched from Cape Canaveral, Florida by rocket before a 10-month solar powered trip, which should reach Mars on Sunday, September 21.
As the spacecraft approaches Mars, wrapping up an interplanetary journey of 442 million miles (711 million kilometers), six thruster engines will fire briefly.
Then the six main engines will ignite two by two in quick succession and will burn for 33 minutes to slow the craft, allowing it to be captured in an egg-shaped orbit.
Once Maven slows, it will deploy its scientific instruments to collect data on how Mars changed from a warm and wet world earlier in its history, and died, to become the cold dry planet it is now.