Satellite images + lucky boat trip provide new information on glowing “milky seas”

On some moonless nights, vast patches of the northwest Indian Ocean and seas around Indonesia begin to glow. Hundreds of sailors witnessed this event, but only one research vessel, by chance, came across this vital phenomenon, known as the Sailors of the Milky Way. Thanks to this vessel, the samples showed that the light source is bacteria called in Harvey, that colonized microalgae called Phaocystis. But this was Back in 1988And researchers are still in the right place and time to catch one of these events again.

Both bacteria and algae are common in those waters, so it’s not clear what causes these rare events. To help understand why milky seas form, researchers are getting much better at spotting these areas of bioluminescence from the sky. With the help of satellites, Stephen Miller, A professor of atmospheric sciencesboth photographs and eyewitness accounts of the Milky Way were collected for Nearly 20 years. Thanks to improvements in imaging capabilities over the past decades, Miller has published a file last year’s compilation of potential milky seas in the 2012 to 2021 time frame, including one event south of Java, Indonesia, in summer 2019.

But these satellite observations lack surface confirmation – that is, even the yacht’s crew Ganesha They contacted Miller through their first-hand account of what they experienced during their overseas trip around Java in August, which was recently published in PNAS. Eyewitness evidence – along with the first images of a Milky Sea – shows that these satellites are indeed a powerful tool for detecting these events.

sky eyes

Although milky seas can be huge – greater than 100,000 square kilometers if seen in 2019 – the intensity of this bioluminescence is still relatively weak. By comparison, the known sea litter of marine plankton (dinoflagellates) is 10 times stronger – and even this can be difficult to detect.

To capture the Milky Seas by satellite, researchers like Miller and his collaborators had to wait for the Day/Light Band to be installed on the National Oceanic and Atmospheric Administration (NOAA)’s latest generation of environmental satellites. This imaging device is sensitive enough to capture light 10,000 times weaker than reflected moonlight and about a billion times weaker than reflected sunlight. The Day/Light Bands are installed on two satellites: the Suomi National Polar-Orbating Partnership (launched in 2011) and the Polar Satellite System Series (launched in 2017).

Thanks to these satellites, Miller was able to rummage through 10 years of satellite data, finding 12 suspected seafarers between 2012 and 2021. This data showed that events can last for weeks and that they often coincide with regional monsoons and algae. Blossoms resulting from rising nutrient-rich water.

“While Milky Ways are a stunning visual phenomenon with an interesting historical story linked to marine folklore, I think in the modern era we are very interested in understanding how and why this massive expression of our biosphere, linked to primary production (the basis of the marine food chain),,” he wrote. Miller in an email to Ars Technica. “I would like to translate this into a better awareness of the atmosphere/ocean/biosphere coupling in the Earth’s climate system, so that we can begin to understand how essential components of our planet’s ecosystem respond in a changing climate.”

But all of Miller’s observations were coming from more than 800 km in the sky – until he heard from Ganesha crew.