Nasa

Other articles by Aaron Mackey:

Private colleges growing quickly Payson waits for a university to help fulfill its college hopes Community colleges are key AZ higher ed looking like a new world If state adds grads, will there be enough jobs for them? Higher education in Arizona to transform if money, cooperation materialize Expansion-plan costs concern regents Flandrau center's doors aren't completely closed UA's biggest college gets interim dean Deal lets students pursue bachelor's degrees online

Health Care
Casa de la Luz Hospice
RN Residential Hospice House Manager Sales and Marketing
EVER-READY GLASS
SALES REPS Health Care
CHILDREN'S CLINICS
MEDICAL RECORDS SUPERVISOR Health Care
CODAC
MULTIPLE HEALTHCARE OPPORTUNITIES Education
VAIL SCHOOL DISTRICT
SAFETY COORDINATOR Health Care
COPE BEHAVIORAL SERVICES
MULTIPEL POSITIONS Finance and Accounting
FLOWERS, RIEGER & ASSOCIATES
TAX STAFF

Rust-colored soil in Mars' arctic region mixed with liquid water in the past, according to several articles published by researchers with the UA-led Phoenix Mars Mission.

The research, published Thursday in the journal Science, confirms and expands upon preliminary theories the team formed while the spacecraft dug into the planet's surface last summer and physically confirmed the presence of water on Mars.

At some point in the planet's past, liquid water combined with soil to form minerals and other compounds.

When the water froze, the minerals left behind provided telltale signs for Phoenix scientists that prove Mars had a wet period at some point, Peter Smith, the University of Arizona scientist who led the scientific mission, said in an interview Thursday.

"It wasn't just a frozen, dry environment like we see today," he said. "There was a warmer, wetter time on Mars."

The most-likely cause of the melting was when the planet's axis tilted toward the sun, creating a warmer environment near the north pole.

Smith estimates that the tilt occurs for a short time every 5 million years or so.

During those periods, the arctic region of Mars would be most hospitable to life, Smith said.

While Phoenix wasn't equipped to find evidence of life on Mars, the research published should help scientists answer that question.

"We are closing in on finding evidence that Mars might be habitable," Smith said.

The tilt of the axis isn't the only time liquid water might have existed on the planet, the published research indicates.

A large impact of either a comet or asteroid near Phoenix's landing site half a billion years ago melted polar ice that created a sheet of water and dust that flowed through a shallow valley, Smith said.

It's also likely that water vapor in the atmosphere moved into the soil and froze, helping form the large sheet of subsurface ice around the polar region.

While many of the conclusions reached in the research papers have been public for months, publishing them formally in a journal is the first step toward broader engagement with the scientific community, Smith said.

The research sets the stage for larger discussions about just what Phoenix found and whether life could have existed on the planet, Smith said.

"This is not the end of Phoenix," he said.