Mars landing 2021: How far away is Mars?
There are three missions to Mars happening in 2021.
China's Tianwen-1 is due to land a rover on the red planet in May.
But how far away is Mars? And why is landing on Mars known as the "seven minutes of terror"?
Here BBC Science Correspondent Laura Foster explains how long it takes to get there and why it's so difficult.
Video by Laura Foster, Megan Fisher and Terry Saunders.