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LITTLETON, Colo. — Ten months after launching from Earth, an unmanned spacecraft known as Maven reached Mars on Sunday night.

The mission, which is designed to focus on Mars’ atmospheric conditions, involves several scientists and researchers based in Colorado.

On Sunday night, dozens of Maven employees watched as the spacecraft used its rocket boosters to enter the Martian atmosphere. The craft will fly around the red planet for the next year and send data back to Earth once a week.

Researchers hope Maven will help explain why Mars no longer contains water on its surface compared to Earth. Scientists with Lockheed Martin in Littleton and researchers at the University of Colorado played a major role in the project.

Maven — the Mars Atmosphere and Volatile Evolution craft — traveled 442 million miles to reach Mars’ orbit.

It is the first mission devoted to studying the upper Martian atmosphere as a key to understanding the history of Mars’ climate, water and habitability.

“The evidence shows that the Mars atmosphere today is a cold, dry environment, one where liquid water really can’t exist in a stable state,” said Bruce Jakosky, Maven principal investigator, during a mission preview briefing last week at NASA headquarters in Washington. “But it also tells us when we look at older surfaces, that the ancient surfaces had liquid water flowing over it.”

So where did the planet’s water and carbon dioxide go?

Jakosky said Maven will help unravel that mystery by using its scientific instruments to measure the composition and escape of gases in the Martian atmosphere.

Maven is to study the top of the atmosphere to determine the extent to which losing gas to space might have been the driving mechanism behind climate change, Jakosky said.

For the next year, the craft will gather data so scientists can determine why Mars no longer maintains the climate it once had. Scientists believe 3 billion years ago, Mars looked similar to Earth with vast supplies of water.

Once a week, Maven will send back data to Earth about Mars’ atmospheric conditions. The data will then be collected in Colorado at the same place Maven was built. Researchers call it a proud day not just for Colorado but for anyone who has ever been curious about the red planet.

Maven has company out near Mars, man-made and otherwise.

India’s first mission to the Red Planet, the Mars Orbiter Mission, is set to arrive a few days after Maven does. The director of NASA’s Planetary Science Division, Jim Green, says the United States and India are interested in cooperating as their crafts gather data about the planet.

There’s a visitor of the cosmic kind, too.

Comet Sliding Spring, which was discovered last year, will be closest to Mars about four weeks after Maven arrives.

The comet is going to miss Mars by about 81,000 miles, Jakosky said.

“I’m told that the odds of having an approach that close to Mars are about one-in-a-million years,” he said, adding that dust from the comet carries only a “relatively minimal” risk to the spacecraft.

Maven will take advantage of the rare flyby by observing the comet itself, as well as its effect on the Martian atmosphere.