Nasa's MAVEN Probe to Enter Mars Orbit on September 21

The Mars Atmosphere and Volatile Evolution (MAVEN) probe is different from past Nasa missions because it focuses on the mysteries of the never-before-studied upper atmosphere.

It is designed to investigate what happened to the carbon dioxide in air and the water on the surface to transform what was once a wet, warm planet to a dry, cool one.

MAVEN's findings are expected to help pave the way for a future visit by humans to the Red Planet, perhaps as early as 2030.

MAVEN has traveled 442 million miles (711 million kilometers) and is nearly ready to make its way into Mars' orbit, Nasa said Wednesday.

The orbit-insertion maneuver is scheduled for 9:50 pm Eastern Daylight Time on Sunday (0150 GMT Monday), the US space agency said.

It will "begin with the brief firing of six small thruster engines to steady the spacecraft," Nasa said in a statement.

"The engines will ignite and burn for 33 minutes to slow the craft, allowing it to be pulled into an elliptical orbit with a period of 35 hours."

Once MAVEN begins circling Mars, it will enter a six-week phase for tests.

"Thereafter, MAVEN will begin its one-Earth-year primary mission to take measurements of the composition, structure and escape of gases in Mars' upper atmosphere and its interaction with the sun and solar wind."

Much of MAVEN's year-long mission will be spent circling the planet 6,000 kilometers above the surface.

However, it will execute five deep dips to a distance of just 125 kilometers above the Martian landscape to get readings of the atmosphere at various levels.

"The MAVEN science mission focuses on answering questions about what happened to the water and carbon dioxide present in the Mars system several billion years ago," said Bruce Jakosky, MAVEN principal investigator from Colorado University-Boulder's Laboratory for Atmospheric and Space Physics.

"These are important questions for understanding the history of Mars, its climate and its potential to support at least microbial life."