Right now, NASA scientists are biting their nails with nerves and, if it's possible to do both at the same time, hyperventilating with excitement. They're excited because after travelling 352 million miles through the solar system, their Mars lander, Curiosity, is approaching its target.
But they're nervous because that landing is the riskiest they've ever attempted. What's more this $2.5 billion mission is NASA's last visit to Martian soil for the foreseeable future.
There are no more missions on the books. Full stop. Europe intends to land a rover on Mars in 2018.
Michael Meyer, NASA's lead scientist for Mars Exploration says "I can't wait". And he won't have to wait long, Curiosity is due to touch down at 06.31 our time on Monday morning.
But NASA has been forced to adopt a new, untested, and high-risk landing strategy. Why? Because Curiosity is a real heavyweight, five times heavier than the last NASA Mars rover, weighing in at a tonne. Why? Because Curiosity is a mobile geology lab, bristling with cameras and analytical instruments, as well as a laser and a drill to "sniff" samples of Martian Soil
The logic is this: Planetary scientists know there was once water on Mars. They can see that because there are deposits, like Clay, that are laid down only in water. And there are geological features that look like they've been shaped by water.
What they don't know is whether that water was ever in Martian history the right kind of water to support life. Was it too acid? Was it too polluted? Those are the questions Curiosity will answer if it lands in one piece.
It has cameras to steer around the surface. It has a laser to vaporise surface rocks and "sniff" the smoke with sophisticated analytical instruments. It has a robot arm, equipped with a drill, to prise samples from Martian rocks and lift them into the mobile lab.
But all that means weight and makes it impossible to land Curiosity in a giant air-big , like they've done before
So instead the landing will be incredibly complex:
- Curiosity will approach Mars at 13, 200 miles an hour.
- It will use the friction of the Martian atmosphere to slow down to around 1,000 mph.
- Its computers will then trigger a 70 ft nylon parachute, the biggest ever built.
- The parachute will slow it down to about the speed of Concorde.
- A mile above the surface, the parachute will be jettisoned and 8 retrorockets will fire to slow it even more.
- 65 ft above the surface the rover will be lowered on three Kevlar cables from a "flying bedstead" NASA call a sky crane
- Once it touches down the bedstead shoots off out of harm's way.
Complex. You bet it is.
What's worse the whole 7 minute sequence has to be controlled by onboard computers. NASA engineers at the Jet Propulsion Lab in Pasadena will have no control, that's why they're biting their nails.
And they know there's no back-up for a landing system that works in computer simulations but might well not in the real world of Mars.