NASA Sensor On Space Station Detects Contamination Off California Coast [View all]

By Joji Xavier ✉ | Published: 6/16/2025 9:57 AM ET



An instrument built at NASA's Jet Propulsion Laboratory to map minerals on Earth is now revealing clues about water quality. A recent study found that EMIT, or Earth Surface Mineral Dust Source Investigation, was able to identify signs of sewage in the water at a Southern California beach.

The authors of the study examined a large wastewater plume at the mouth of the Tijuana River, south of Imperial Beach near San Diego. Every year, millions of gallons of treated and untreated sewage enter the river, which carries pollutants through communities and a national reserve on the U.S.-Mexico border before emptying into the Pacific Ocean. Contaminated coastal waters have been known to impact human health — from beachgoers to U.S. Navy trainees — and harm marine ecosystems, fisheries, and wildlife.

For decades scientists have tracked water quality issues like harmful algal blooms using satellite instruments that analyze ocean color. Shades that range from vibrant red to bright green can reveal the presence of algae and phytoplankton. But other pollutants and harmful bacteria are more difficult to monitor because they're harder to distinguish with traditional satellite sensors.

The introduction of EMIT marks the difference, NASA says. The hyperspectral instrument orbits Earth aboard the International Space Station, observing sunlight reflecting off the planet below.

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