WASHINGTON: Are we alone? Or was there life on another planet? Nasa's $2.5 billion dream machine, the Mars Science Laboratory, aims to take the first steps toward finding out when it nears Mars's surface on Monday.

The planet is Earth's closest neighbor, and scientists have found signs of water there, hinting that some form of life was once likely, even though Mars is now a dry place with a thin atmosphere, extreme winters and dust storms.

Nasa said it will find out if its Mars Science Laboratory and rover, Curiosity — designed to hunt for soil-based signatures of life and send back data to prepare for a future human mission — landed safely at 1:31 am Eastern time (0531 GMT) on Monday.

That will be about 14 minutes after the touchdown actually happens due to the time it takes for spacecraft signals to travel from Mars to Earth.

As of late Saturday, the laboratory was approximately 261,000 miles (420,039 kilometers) from Mars, closing in at around 8,000 miles per hour (13,000 kilometers per hour).

“Curiosity remains in good health with all systems operating as expected,” Nasa said in a statement.

The nuclear-powered rover is the biggest ever built for planetary exploration, weighing in at one ton, about the size of a small car, and carries a complex chemistry kit to zap rocks, drill soil and test for radiation.