The new approach to landing a rover on the planet, to be attempted in August, will involve winching it slowly to the surface using nylon ropes attached to a spacecraft overhead.
Once the probe, named Curiosity, has safely reached the ground the 25ft-long cords will be cut and the parent ship will use rockets to fire itself well away from the probe for a crash landing.
The new tactic is an attempt to overcome the challenging nature of landing on another planet with several previous missions, including Britain’s Beagle 2 in 2003, having failed in either their approach or landing.
But Nasa experts admitted the project, which will come to a head during the attempted landing on August 6, is a gamble which could prove to be a £1.7 billion ($2.5bn) disaster, The Independent reported.
Speaking at a news conference in London ahead of a lecture to the Royal Academy of Engineering Charles Elachi, director of the Nasa Jet Propulsion Laboratory in California, said: “We will be very nervous. Landing on another planet is not a walk in the park.”
To make the landing attempt a success, scientists will have six minutes in which to slow the 3 tonne craft travelling at 12,000mph enough to allow a soft landing.
Mr Elachi said: “We usually call it the six minutes of terror. When you are coming in at 12,000mph with that kind of mass it’s equivalent in terms of energy to 25 high-speed trains going at full speed.”
The team will also have to perform the task at exactly the right angle, with a level of accuracy equivalent to hitting a golf ball from Los Angeles to Scotland and scoring a hole-in-one, he added.
Previous landing attempts have used airbags to cushion the landing but the new rover is too big to allow this method to work, creating the need for the new “sky crane” technique, he said.
If its landing is successful, the probe will land at the base of a mountain in the Gale crater where it will study sediment which scientists believe could have been made by running water – a sign that life could have once existed on the planet.