The rover "Curiosity" has landed on Mars.
NASA said it received a signal from "Curiosity" after a dramatic descent into the Martian atmosphere.
"Curiosity" has already beamed back its first images from the Martian surface.
The rover will now undergo several weeks of engineering checks before starting its surface mission.
Once ready, it will collect rock and soil samples over the next two years to explore whether the planet's environment could have supported life in the form of microscopic organisms.
NASA administrator Charles Bolden told a news conference following the landing that "the wheels of 'Curiosity' have begun to blaze the trail for human footprints on Mars.
"The most sophisticated rover ever built, ['Curiosity'] is now on the surface of the red planet where it will seek to answer age-old questions about whether life ever existed there on Mars, or if the planet can sustain life in the future."
"Curiosity's" landing is one of the most complex ever achieved in robotic spaceflight.
Due to its bulky size and weight -- one ton -- engineers had to use cables to lower the rover inside of a giant crater.
An artist's concept depicts the rover "Curiosity," of NASA's Mars Science Laboratory mission, as it uses its Chemistry and Camera (ChemCam) instrument to investigate the composition of a rock surface.
Mission controllers at the Jet Propulsion Laboratory near Los Angeles burst into applause as they received confirmation that "Curiosity" had successfully landed on Mars.
Landing on the red planet is extremely tricky.
There have been more than 30 attempts by different nations to land on Mars since the 1960s, but more than half have failed.
U.S. President Barack Obama hailed "Curiosity"'s landing as historic and "an unprecedented feat of technology."
The landing capped a journey of more than eight months across more than 560 million kilometers of space.
The "Curiosity" rover is the most ambitious and priciest Mars mission yet. The $2.5 billion project, formally called the Mars Science Laboratory, is NASA's first astrobiology mission since the 1970s-era Viking probes.
The Mars landing marks a major victory for the U.S. space agency, badly hit by budget cuts and the recent loss of its 30-year-old space shuttle program.