NASA - National Aeronautics and Space Administration

Who Are NASA's Earth Explorers? The elementary school student wondering how El Niño will affect tomorrow's weather. The scientist studying connections between ozone and climate change. And the farmer using satellite pictures to keep track of crops. All of these people are Earth Explorers -- they are all curious about the Earth system. This monthly series will introduce you to NASA Earth Explorers, young and old, with many backgrounds and interests. Nominate an Earth Explorer! Tell us about the Earth Explorers you know. We're looking for students, teachers, scientists and others who are working with NASA Earth science data and imagery to better understand our home planet. Send your nominations to Dan Stillman: dan_stillman@strategies.org.

Heidi is an ocean scientist. She works both under water and on dry land. The view is the same for Heidi in both places. She doesn't see as many females as she would like.

More and more girls are studying ocean and Earth science. Still, there are fewer women than men. Heidi wonders why. She thinks girls can do anything guys can do. That's what she tells her two daughters. Their ages are 5 and 3.

"We … need to do better to encourage girls in the math and sciences," she said.

Image above: Heidi Dierssen cruises the shallow ocean waters off the southern tip of Florida. Credit: Heidi Dierssen

Heidi is doing her part. She's a good role model for girls who want to do math and science. She studies seagrass for NASA. Seagrass is like the grass you see in your yard. Except it grows at the bottom of the ocean.

Seagrass is important. It provides food for many animals in the water. It gives them a place to live. It also helps keep the water clean. And it protects the shore from damage caused by waves.

But, there's a problem. There is not as much seagrass now as there used to be. There are many reasons for this. Two of them are pollution and boating. Another one is disease.

Heidi is worried about the loss of seagrass. So are other scientists. They want to keep track of seagrass all over the world. That's where satellites come in. Satellites look down on Earth from space. They are great for watching the surface of the ocean. But it's hard for them to see through to the bottom.

Image above: Grids like this one help Heidi measure the amount of seagrass on the ocean floor. Credit: Laura Bodensteiner

So how can satellites help with seagrass? It turns out we can learn a lot from the ocean's surface. Its color can give us clues about what lies beneath. But how can we know for sure if it's seagrass? We can't. At least not until someone goes to check.

For Heidi, that means getting wet. She spends a lot of time on or in the water. She takes pictures of the seafloor. She measures how light passes through the water. And she measures how it reflects off the ocean bottom. She also collects water to look at later.

All of this information is very useful. It helps to match ocean color with seagrass amount. Knowing where and how much seagrass there is has its value. It can show how healthy a fishing area is. And it can show how well projects are doing that replant seagrass.

The water Heidi dives into is fairly warm. And it's only 3 to 5 meters (10 to 15 feet) deep. But there are some risks. The currents can be strong. And there are some fish that are way too friendly.

Image above: Divers must keep an eye out for fish and strong currents. Credit: Laura Bodensteiner

"One time ... a remora (also known as a suckerfish) came flying at me from the left and tried to attach itself to my bottom lip," she said. "'Ouch!' I think I screamed underwater. It apparently mistook me for a shark."

Still, Heidi says she loves her time at sea. The only part she doesn't like is being away from her family. Each trip to the ocean can last about two to three weeks. She thinks a lot about her daughters during that time. She says she wants to show them that girls can do it all. They can have success in their job. And they can also raise a family.

She says she wants her kids and other girls "to achieve all they can in life, including math and science. I want to ... let them know that they can have a positive impact on the world."

See previous Earth Explorers articles:
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Related Resource
Water Around the World
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Dan Stillman, Institute for Global Environmental Strategies