NASA's Mars rover Curiosity, loaded with the most-sophisticated instruments ever used to explore another world, touched down on the Red Planet early Monday morning, on a quest for signs of whether the Red Planet has evidence of past and present habitable environments.

Photo taken on June 10, 2012 shows a scientist introduce Curiosity rover to visitors

at the Jet Propulsion Laboratory (JPL) of NASA in Pasadena, California, the United States.

NASA's Mars rover Curiosity, loaded with the most sophisticated instruments ever used to explore another world,

touched down in the Red Planet early Aug. 6, 2012, on a quest for signs of whether

it has evidence of past and present habitable environments.

A chorus of cheers and applause echoed through NASA's Jet Propulsion Laboratory (JPL), which manages the mission, after the rover sent a signal to Earth, NASA TV shows.

"Curiosity rover has landed on Mars... The time of day at the landing site is mid-afternoon -- about 3 p.m. local Mars time at Gale Crate," the U.S. space agency announced.

"It's an enormous step forward in planetary exploration. Nobody has ever done anything like this," said John Holdren, top science advisor to President Barack Obama, who was visiting JPL for the event. "It was an incredible performance."

Minutes later, Curiosity beamed back the first pictures from the surface showing its wheel and its shadow, cast by the afternoon sun -- giving earthlings their first glimpse of a touchdown on another world.

"I can't believe this. This is unbelievable," said Allen Chen, deputy leader of the rover's descent and landing team.

Curiosity landed near the base of a layered mountain three miles (five kilometers) high inside the Gale Crater on Mars. The crater spans almost 100 miles -- an area as large as Connecticut and Rhode Island combined.

Planetary geologists are intrigued because data from the U.S. Mars Reconnaissance Orbiter suggest the low-lying crater floor once was wet with water. Scientists also think the site might be rife with "organics" -- carbonaceous compounds that are key chemical building blocks for life.

Traditional Mars space-trucks including Sojourner, Spirit and Opportunity were dropped onto a lovely air-bag to cushion their fall, the de facto landing experience for a rover. But Curiosity is huge -- the size of a mini cooper -- so air bags are not its thing.

Instead, the rover was lowered onto the Martian surface by a "sky crane".

NASA has dubbed that fall from space "Seven Minutes of Terror" in a video describing the onrushing event.

At nearly a ton, the six-wheeled vehicle dwarfs all previous robots sent to the surface of the planet. It is about twice as long and more than five times as heavy as any previous Mars rover.

The nuclear-powered Curiosity is 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 detector to measure dangerous radiation on the surface. It also tracked radiation levels during the journey to help NASA better understand the risks astronauts could face on a future manned trip.

The rover is equipped with a generator that converts heat from the natural decay of a non-weapons-grade plutonium into electricity. The electricity will power rover systems and keep it warm in an environment where average temperatures are minus 64 degrees Fahrenheit (minus 53 degrees Celsius).

After several weeks of health checkups, the rover could take its first short drive and flex its robotic arm. During a prime mission lasting one Martian year -- nearly two Earth years -- researchers will use the rover's tools to study whether the landing region has had environmental conditions favorable for supporting microbial life and favorable for preserving clues about whether life existed.

The 2.5-billion-U.S.-dollar Mars Science Laboratory, the formal name of the mission deploying the Curiosity rover, was launched from Cape Canaveral in Florida, on Nov.26, 2011. The launch came at a time when NASA -- still struggling to find its way after the retirement of America's iconic shuttle fleet -- was anxious to exhibit its technological competence and prowess.

In February, because of its cost, the United States backed out of the Mars Sample Return mission, a project coordinated with the European Space Agency meant to bring back Martian soil and rocks to be examined in local labs.

After Curiosity, the only planned U.S. mission to Mars is an atmospheric orbiter meant to launch next year.

Mars is the chief component of NASA's long-term deep space exploration plans. Obama has set a goal for astronauts to orbit Mars by the mid-2030s followed by a landing. Before that can happen, the plan is to send astronauts to an asteroid first.

VietNamNet/Xinhuanet