Why NASA Spent Millions of Dollars on a Satellite to Look at Dirt on the Ground

​This morning, after a two-day delay, NASA launched ​a new satellite into orbit that will spend the next three years studying the moisture within the top two inches of the Earth's soil.

Now, you might be asking yourself, "Why would NASA spend millions of dollars and fire a satellite into orbit just to look at dirt on the ground back on Earth?" I was wondering the same thing, so I talked to the scientist in charge of the mission.

It turns out there's actually a lot we don't understand about the moisture that lives in our soil, and that knowledge could unlock mysteries about about the environment, our food, and even parasitic diseases.

"This is really important for science in a lot of different areas," said Jared Entin, the program scientist for the ​Soil Moisture Active Passive mission, or SMAP. "There are a lot of people who are anticipating this because it's one of the missing pieces of our global observing network."

Entin told me while monitoring of soil moisture in the United States is fairly sophisticated, there's no system in place that enables measuring soil moisture across the globe. Moisture in the ground plays an important role in major Earth cycles, he said: the water cycle, energy cycle, and carbon cycle. Water gets evaporated into the atmosphere to cause precipitation as well as providing moisture to plants, which in turn convert carbon dioxide into oxygen.

"It serves as a cog between those cycles," Entin said. Measuring how much moisture is in the soil at various points in the day, week, season, and year all across the globe will provide a pool of data never reached before that can provide insight into a wide range of processes back on Earth.

For one, the data will help refine both climate change and weather forecast models—meaning we'll have more consensus on how climate change will present itself over the years and months to come as well as more precise forecasts for our daily and seasonal weather.

It can also be used to predict droughts and floods before they happen, all over the world, which can impact agriculture and the economy. Entin said dozens of agencies, from John Deere to the US military, have signed on to get access to the data to improve their operations.

SMAP will also be able to measure water on the soil surface, which is important for our understanding of vector-borne diseases like ​malaria and West Nile, which are transmitted by mosquitos, ticks, and fleas that breed in still pools of water.

Once the mission is complete, Entin and the SMAP team believe the satellite will likely still be functional for a decade or longer. If everything is still running smoothly, they hope the expand the scope of data SMAP collects to include ocean currents and wind speeds around the globe. SMAP could be the world's eye in the sky for a host of environmental and ecological patterns.

"Not all of the things we do at NASA have wide range applications in science and for decision-makers. Some are a little more narrow. But SMAP I would say is on the wider side. It has pretty broad potential to be used by a lot of different communities, so we're really, really excited by that," Entin said.