NASA scientists celebrated this morning as the Mars explorer, Curiosity, touched down safely on the Red Planet.

Cheers and applause echoed through the Nasa HQ in California after the most hi-tech interplanetary rover ever built signalled it had survived its 13,000mph plunge through the thin Mars atmosphere.

"Touchdown confirmed," said engineer Allen Chen. "We're safe on Mars."

Minutes later, Curiosity beamed back the first black-and-white pictures from the surface of Mars, showing its wheel and its shadow, cast by the afternoon sun.

President Barack Obama tweeted his appreciation: "I congratulate and thank all the men and women of Nasa who made this remarkable accomplishment a reality."

Over the next two years, Curiosity will explore the planet's surface, examine rocks and scoop up rust-tinted soil to see if the region ever had the right environment for microscopic organisms to thrive.

It is the latest chapter in the long-running quest to find out whether primitive life arose early in the planet's history.

The voyage to Mars took more than eight months and spanned 352 million miles.

The nuclear-powered Curiosity weighs a tonne, is the size of a small car and iis packed with scientific tools, cameras and a weather station.

It sports a robotic arm with a power drill, a laser that can zap distant rocks, a chemistry lab to sniff for the chemical building blocks of life and a radiation detector.

Over the next few days, Curiosity is expected to send back the first colour pictures