Scientists compared EMIT’s observations of the Tijuana River plume with water samples they tested on the ground. Both EMIT and the ground-based instruments detected a spectral fingerprint pointing to phycocyanin, a pigment in cyanobacteria, an organism that can sicken humans and animals that ingest or inhale it.
‘Smoking Gun’
Many beachgoers are already familiar with online water-quality dashboards, which often rely on samples collected in the field, said Christine Lee, a scientist at JPL in Southern California and a coauthor of the study. She noted the potential for EMIT to complement these efforts.
“From orbit you are able to look down and see that a wastewater plume is extending into places you haven’t sampled,” Lee said. “It’s like a diagnostic at the doctor’s office that tells you, ‘Hey, let’s take a closer look at this.’”
Lead author Eva Scrivner, a doctoral student at the University of Connecticut, said that the findings “show a ‘smoking gun’ of sorts for wastewater in the Tijuana River plume.” Scrivner, who led the study while at San Diego State University, added that EMIT could be useful for filling data gaps around intensely polluted sites where traditional water sampling takes a lot of time and money.
EMIT’s Many Uses
The technology behind EMIT is called imaging spectroscopy, which was pioneered at JPL in the 1980s. Imaging spectrometers developed at JPL over the decades have been used to support areas ranging from agriculture to forest health and firefighting.
When EMIT was launched in July 2022, it was solely aimed at mapping minerals and dust in Earth’s desert regions. That same sensitivity enabled it to spot the phycocyanin pigments off the California coast.
Scrivner hadn’t anticipated that an instrument initially devoted to exploring land could reveal insights about water. “The fact that EMIT’s findings over the coast are consistent with measurements in the field is compelling to water scientists,” she said. “It’s really exciting.”
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