Tom HappVerified account

So let me tell you about my favourite and most terrifying thing of Mars missions: it’s a process we call 7 minutes of terror. 7 minutes, because it takes 7 minutes from a spacecraft hitting the atmosphere until it lands, but our radio transmission takes 14 minutes...pic.twitter.com/oGkc5n3E5C

That means for 7 long and excruciating minutes, we have no idea whether a mission has made it to the surface intact or whether we have failed. The work of many many people for many many years is on the line and we wait for 7 agonising minutes to know.pic.twitter.com/GOR2sbq2Xd

To land anything on Mars, thousands of small steps have to go perfectly right. I’ll walk you through the basics: after flying for 300 million miles, a spacecraft sent from earth has to enter Mars’ atmosphere in an exact 12 degree angle - that’s almost as flat as an airplane.pic.twitter.com/DpVcNI5VCx

Any steeper and our spacecraft burns to ashes. Any more shallow and it literally just bounces off the atmosphere. There is no middle ground here, it HAS to be exact to work in the first place or the work of hundreds of people and years of work will not end in success.pic.twitter.com/jpf35obJRj

Once it has hit the atmosphere, the spacecraft needs to decelerate from 20.000 km/h to 1600 km/h to land. There’s incredible forces at work here. In fact, that’s 12 earth-Gs in about 2 minutes - those are some back-breaking numbers.pic.twitter.com/hGGnZ1uInC

Deceleration in such a short amount of time means there will be heat - A LOT OF IT! The heat shield has to withstand up to 1200 degrees Celsius during its decent - that’s hot enough to melt steel to a useless clump.pic.twitter.com/IW31uoO286

To slow down further, the spacecraft deploys a GIGANTIC parachute. A supersonic one to be exact - the largest one we’ve ever built. All of those steps are about slowing down the spacecraft, so we’re also blasting off the heat shield once we don’t need it anymore.pic.twitter.com/BVo6RL1PO4

At this stage, the lander has to actually get rid of the backshell with its parachute so it can land safely without getting crushed by the shell or the giant parachute. From here, we have to work with retro boosters to land vertically on the surface.pic.twitter.com/y7zxIaQpSy