A high-tech science laboratory is due to land soon on Mars. Scientists hope to discover clues as to whether life of some kind may have once existed on the Red Planet.
The nuclear-powered Mars rover Curiosity is on track for a precise, safe landing on Monday morning European time, NASA scientists said.
"Curiosity remains in good health with all systems operating as expected," NASA said in a statement.
"We're on target to fly through the eye of the needle," Arthur Amador, the Mars Science Laboratory mission manager told reporters some 36 hours before the landing, alluding to the extremely risky and complex nature of the touchdown.
Most past attempts to send spacecraft to Mars have failed.
After an eight-month voyage of more than 567 million kilometers (350 million miles), the $2.5-billion (2 billion-euro) laboratory is due to touch down at 0531 GMT on Monday.
'Minutes of terror'
The landing involves entering Mars' atmosphere at 21,240 kilometers per hour (13,200 mph), slowing down with the help of supersonic parachutes and being lowered to the surface on nylon tethers by a never-before-used jet-powered "sky crane."
NASA has refered to the final moments of the descent and landing as "seven minutes of terror."
"This is the most challenging landing we've ever attempted," said Doug McCuistion, NASA's Mars Exploration Program director.
However, flight controllers predict favorable weather conditions for the landing at Gale Crater, which is to take place late in the Martian afternoon.
If the landing is successful, the flight controllers at the Jet Propulsion Laboratory near Los Angeles will be quickly informed by a radio transmission relayed via the Mars orbiter Odyssey flying overhead.
If no landing signal comes, it could be hours or days before they know whether this was caused by a mere disruption of radio communications or the rover was damaged in descent or while landing.
Given that all goes well, scientists hope the rover will be able to climb a nearby mountain to search for sediment layers that could be up to a billion years old. The one-ton vehicle is designed primarily to search for soil-based evidence that Mars - the planet most similar to Earth - may have once hosted the ingredients necessary for microbial life to evolve.
Mars is sometimes Earth's closest neighbor, depending on the planets' orbiting patterns, though Venus is the planet which at times can come closest to Earth. Scientists have already found signs of water there, an indication that some form of life may well have once existed on the planet.
Mars is now extremely dry and has only a thin atmosphere. It also has very harsh winters and dust storms, all of which currently make it inhospitable to life as we know it.
tj/ccp (AFP, Reuters)