Artist’s concept of NASA’s Maven spacecraft approaching Mars. NASA/GSFC

Excerpt from AP.

CAPE CANAVERAL, Fla. — Mars, get ready for another visitor or two.

This weekend, NASA’s Maven spacecraft will reach the red planet following a 10-month journey spanning 442 million miles. If all goes well, the robotic explorer will hit the brakes and into Martian orbit Sunday night.

“I’m all on pins and needles. This is a critical event,” NASA’s director of planetary science, Jim , said Wednesday.
Maven is not designed to land; rather, it will study Mars’ upper atmosphere from orbit.

Scientists want to learn how Mars went from a , wet world that may have harbored microbial life during its first billion , to the , barren place of today. Maven should explain the atmospheric changes that led to this radical climate change.
“Where did the water go? Where did the CO2 go from that early ?” said chief investigator Bruce Jakosky of the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder.

“We measure these things today even though the processes we’re interested in operated billions of years ago,” he said.
NASA launched Maven from Cape Canaveral last on the $671 million mission, the first dedicated to studying the Martian upper atmosphere.

ksc_111813_maven_launch_crop.jpg
The United Launch Alliance Atlas V rocket lifts off from Space Launch Complex-41 at Cape Canaveral Air Force on Mon., Nov. 18, 2013, carrying the Mars Atmosphere and Volatile , or MAVEN, spacecraft on a 10-month journey to the Red Planet.
NASA

As of Wednesday, the spacecraft was less than 750,000 miles from its destination; Maven’s view of the red planet would be equivalent to a baseball about 52 feet away.