UP CLOSE, ALGAE looks like a scummy version of grass—slippery, mucky, and just downright disgusting. From far away, though, it creates an impressive cloud of living soft color, gently drifting underwater. From a satellite's point of view, hundreds of miles above Earth, algal blooms are lovely to look at. Yet they pose a wicked danger to human health if left unchecked. 

Yesterday, NASA announced a new $3.6 million project to observe and measure the threat of algal blooms to freshwaters around the United States—by turning to the beautiful, sky-high images from the agency's satellites. In collaboration with the Environmental Protection Agency, US Geological Survey, and the National Oceanic and Atmospheric Administration, researchers plan to collect and analyze satellite imagery stretching back as far as 2002. They'll also collect current pictures of freshwater environments, with a specific mission to track the intensity and frequency of algal blooms.

These soft growths of photosynthetic stuff don't immediately look dangerous, but they can do major damage to freshwater systems. Algae are just like other chlorophyll-filled plants, sucking up carbon dioxide and spewing out oxygen. In the atmosphere, that's a good thing, but too much oxygen in water can poison fish and marine mammals. And when algae die, increased bacterial populations use up dissolved oxygen in the water, leading to dangerously low levels of oxygen.