South River High School senior Erin Frey spent a fair amount of the past school year thinking about Mars and water. Specifically, she wondered how much water had been needed to create gullies on the planet.

She asked that question recently at the Intel International Science and Engineering Fair in Portland, Ore., where she presented her final high school science project.

Her project, "Water on Mars: How Much Then, How Much Now?" won her a fourth-place prize in the category of earth and space sciences, along with $500.

Frey, who will attend Harvard University in the fall, was one of 1,300 high school students from around the world who competed for a total of $3 million in prize money in what is largely considered an elite contest and resume enhancer for future collegians.

Frey was confident about her Mars project, a continuation of an experiment she entered in last year's Intel competition.

Simply put, she set out to estimate the amount of water needed on Mars to etch the gullies or channels that are relatively recent erosional features thought to be caused by groundwater seepage, Frey said. The gullies are generally seen in the sides of craters and other cliff-like areas.

The experience of developing, researching and testing her project was thrilling, and not just because she likes science.

"Every year that I've gone to the fair, I've loved it," said Frey, 17, adding that she especially enjoyed meeting her fellow competitors. "These kids are not what you think. They don't fit the stereotype of science nerds. They don't just live and breathe science."

But, like Frey, they do dabble in it quite a bit.

Frey picked up some of her love of science from her parents. Her mother, Denise Frey, is a computer scientist. Her father, Herbert Frey, heads the Geodynamics Branch at NASA's Goddard Space Flight Center in Greenbelt.

Frey, who lives in Gambrills, said she became serious about her science fair project after learning that South River High Principal James Hamilton had a rule: Any student who takes a science class has to do a science project. No problem, she thought at the time.

Frey went to her father and asked if he could help her develop a project. The subject she chose, water on Mars, was an offshoot of research her dad had been doing on the topography of that planet.

"Once I started to study Mars, I was hooked," she said. "I've been doing research on this planet ever since.''

To prepare for last month's Intel competition, Frey researched her subject after school and went with her father to work. There they would discuss ideas and test her hypothesis.

"She's very strong-willed and wants to do her own thing," Herbert Frey said. "Sometimes we disagree, but that's part of science."

Rochelle Slutskin, science coordinator for Anne Arundel County public schools, said determination helped Frey win a prize at the Intel competition. "Erin is devoted to her science," Slutskin said.

She is also devoted to being multi-dimensional.

In addition to being a stellar student, Frey is a principal dancer with the Maryland Ballet Theatre and a recent co-chairman of Rebuilding Together, a community service project that helps refurbish homes for elderly and disabled people.

Frey is also humble. She said that the first time she competed in the Intel contest, "I felt a little inferior. But then I realized that I could really relate to these people and I had a good sense of belonging and community and feeling like I fit in."

Erin Frey's "Water on Mars" project placed fourth at the Intel International Science and Engineering Fair last month in Portland, Ore.