As the Mars rover Curiosity prepares for landing on Aug. 5 after its nine-month, 352-million mile journey through space, UC Davis geology professor Dawn Sumner will be making preparations of her own.

A co-investigator for NASA's Mars Science Laboratory team, Sumner will spend the first four "Martian" days - which are 40 minutes longer than a day on Earth - as the "long-term planner," coordinating the first scientific interpretations of what is seen when the rover lands and helping make daily decisions about the research vehicle's activities.

The role will rotate among Sumner and an international team of scientists during the first three months of the two-year mission.

From the mission's base at the NASA Jet Propulsion Laboratory in Pasadena, Calif., one of Sumner's first tasks likely will be to direct the rover, via computer, to shoot some of the first true color photographs ever taken of the Red Planet. After the first three months, Sumner will continue to work on the mission from UC Davis.

"One of the important parts of this mission for me is to inspire students to ask big, important questions and participate in human endeavors, like exploration of other planets," Sumner said.

At UC Davis, Sumner studies rocks from early Earth, looking for clues to life that may have lived in the surrounding environment.

Her work has taken her to Antarctica, where she studied fossils for signs of past microbial life, the only life forms present for most of Earth's history. Scientists expect that any life on Mars, if it ever existed, has been microbial, as well.

"Antarctica, where I've been, has essentially no life - except us when we're there - and the bacteria," Sumner said. "It's as much like being on another planet as you can get on Earth."

In 2004, her Antarctic research helped land her a spot on the Mars Science Laboratory team, which recognized that her skills could be critical to the mission's goal: to determine whether there ever could have been life on Mars.

Sumner also helped choose the landing site of Gale Crater, near the base of Mount Sharp.

"Gale Crater was chosen because there is a sequence of layers of rocks - much like the Grand Canyon, with each layer representing the environment over time," Sumner said. "This gives us a long history of environments to allow us to evaluate habitability."

Earlier observations of the Gale Crater region by a Mars orbiter identified salt and clay minerals, which form when water interacts with rock. Water is one precondition of life.

"Gale Crater doesn't have evidence of liquid water now," Sumner said. "The rocks there are probably about 3 billion years old. So we're looking at whether life could have existed when the rocks formed."

This mission is NASA's most ambitious Mars project yet. The rover Curiosity is about twice as long and five times the weight of its predecessors, Spirit and Opportunity. Its landing zone is a third as large as that of past missions, requiring extreme precision for landing.

In the last seven minutes of its descent, Curiosity will deploy a parachute, drop its heat shield, fire eight retrorockets, and slow from 13,200 mph to 1.7 mph. A new, rocket-powered "sky crane" will bring the rover to the surface, touching down at 10:31 p.m., PST.

In addition to color cameras, the rover brings with it a host of gadgets - 165 pounds of them - that Mars has never seen before. A rock-zapping laser - one of Sumner's favorite tools - can vaporize rock to study its chemical composition. Other equipment will allow Curiosity to sample rocks and soil, process them, and begin to analyze them.

"If there is life in the universe, and particularly as close as our neighbor planet Mars, it changes our sense of who we are," Sumner said. "To me, that's one of the most important questions scientists can ask - to understand who we are."