Snubbing its nose at the global economic slowdown, NASA on Saturday launched a $2.5 billion nuclear-powered rover toward Mars.

The 20-storey-tall Atlas 5 booster rocket lifted off and shot into space at 10:02 EST, sending Nasa’s Mars Science Laboratory on a 556 million km journey to the “Red Planet.”

The car-sized rover, nicknamed Curiosity, is expected to touch down on August 6, 2012, to begin two years of detailed analysis of a 154 km-wide impact basin near the Martian equator called Gale Crater.

The mission’s goal is to determine if Mars has or ever had environments – in areas known to have contained water – to support life. It is the first astrobiology mission to Mars since the 1970s-era Viking probes.

Scientists chose the landing site because it has a 4.8 km-high mountain of what appeared from orbital imagery and mineral analysis to be layers of rock piled up like the Grand Canyon, each layer testifying to a different period in Mars’ history.

The rover has 17 cameras and 10 science instruments, including chemistry labs, to identify elements in soil and rock samples to be dug up by the probe’s drill-tipped robotic arm.

Launch is generally considered the riskiest part of a mission, but Curiosity’s landing on Mars will not be without drama.

The 898 kg rover is too big for the airbag or thruster-rocket landings used on previous Mars probes, so engineers designed a rocket-powered “sky-crane” to gently lower Curiosity to the crater’s floor via a 13m-long cable.

“We call it the ‘six-minutes of terror,'” said Doug McCuistion, director of Nasa’s Mars Exploration Program, referring to the risky landing.

“It is pretty scary, but my confidence level is really high,” he added.

Curiosity’s mission is designed to last one Martian year, or 687 Earth days.