Engineers at NASA's jet propulsion lab will later today try to steer a car-sized robotic rover to a tricky landing on Mars.
The rover Curiosity is headed for a two-year mission to study whether Mars ever had the elements needed for microbial life, but because it weighs 900-kilograms the robot can't land the way previous spacecraft did.
This time NASA is testing a brand new landing that involves gingerly setting down the rover similar to the way heavy-lift helicopters lower huge loads at the end of a cable.
NASA's Jet Propulsion Laboratory engineer Adam Steltzner says the degree of difficulty on the landing is above a 10.
A communication time delay between Mars and Earth means Curiosity will have to nail the landing by itself, following the half million lines of computer code that engineers uploaded to direct its every move.