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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' 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 local time 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 420,039 kilometers from Mars, closing in at around 13,000 km per hour.

"Curiosity remains in good health with all systems operating as expected," NASA said in a statement.

The US space agency added that catalyst bed heaters were in the process of being turned on to prepare the eight Mars Lander Engines that are part of MSL's descent propulsion system.

The nuclear-powered rover is the biggest ever built for planetary exploration, weighing in at 1 ton, about the size of a small car, and carries a complex chemistry kit to zap rocks, drill soil and test for radiation.

The landing is a daring and unprecedented maneuver that involves penetrating the atmosphere at a speed of 21,240 km per hour, slowing down with the help of a supersonic parachute and dropping down gently with tethers from a rocket-powered sky crane.

"This is the most challenging landing we have ever attempted," said Doug McCuistion, director of NASA's Mars Exploration Program.

Two NASA orbiters will be crossing overhead as the lander approaches the surface, and a third orbiter operated by the European Space Agency will also send data back to Earth.

The Mars Science Laboratory began its journey to the Red Planet more than eight months ago when it launched from the Florida coast in late November 2011.

"It gets scarier every day," said McCuistion, noting that only about 40 percent of past attempts by global space agencies to send spacecraft to Mars have succeeded.

"Can we do this? Yeah, I think we can do this. I am confident the team has done an amazing job. We have the A-plus team on this. They have done everything possible to ensure success," he said.

"But that risk still exists. It is going to be tough."

The landing site for the rover is a flat area known as Gale Crater, which lies near a mountain that scientists hope the rover will be able to climb in the search for sediment layers that could be up to one billion years old.

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About the broadcaster:

Rosie Tuck is a copy editor at the China Daily website. She was born in New Zealand and graduated from Auckland University of Technology with a Bachelor of Communications studies majoring in journalism and television. In New Zealand she was working as a junior reporter for the New Zealand state broadcaster TVNZ. She is in Beijing on an Asia New Zealand Foundation grant, working as a journalist in the English news department at the China Daily website.