• Researchers spotted mysterious "slicks" in the Baltic Sea
  • They were actually made up of pine pollen
  • Pollen-rich waters "expanded significantly" in recent years

Scientists have finally cracked the mystery of the "slicks" found in the European Space Agency's (ESA) satellite images. They turned out to be pollen as seen from space.

Satellites can capture some incredible events such as California's wildflower blooms or even the mark of a tornado that has cut through a city. They can even spot bright phytoplankton blooms in the sea, which may look like watercolor paintings. But it turns out that satellites can also capture another, rather under-the-radar, event that one might not think would be visible from space: the proliferation of pollen.

NASA Earth Observatory shared an image captured by the ESA's Sentinel-2A satellite, showing swirls over the Baltic Sea as seen from space. Captured back on May 16, 2018, the image actually is an enhanced view of swirls of pollen, showing just how massive such events can be.

But scientists didn't always know that these "slicks" on the Baltic Sea were pollen, the agency noted. It all started with a "snot event" in the Marmara Sea in 2021, which led researchers to look for signs of the gooey event in other seas as well. That's when they found similar signs in the Baltic Sea even though there were no reports of sea snot in the area at the time.

The team then had a closer look at other satellite data for signs of the mysterious swirls and found that it was actually "distinct" from sea snot and other matter. Further analysis led them to the true culprit behind the slicks: pine pollen.

The researchers shared their findings in a paper published in Remote Sensing of Environment.

This may seem quite concerning for those who suffer from seasonal allergies due to the proliferation of pollen at this time of the year, but the researchers' further findings may sound even more worrisome.

When they looked at satellite springtime images of the Baltic Sea from 2000 to 2021, they found the slick in 14 of the years, with the events being "markedly larger" during the second half of the 22-year period than the first half. The waters that contain the pollen slicks have "expanded significantly" in more recent years — they cover "nearly the entire Baltic Sea," the researchers wrote.

This coincides with the trends of longer pollen seasons with higher pollen production.

A study released in April, for instance, found "widespread advances and lengthening of pollen seasons" and also increased pollen concentrations in North America, "which are strongly coupled to observed warming." In other words, climate change has been worsening pollen seasons in recent decades. This could have "deleterious effects on respiratory health," the researchers said.

Having a view of pollen from space, in a way, highlights just how big these events truly can be. While the exact ramifications of enhanced pollen seasons on people's health and environment remain to be seen, these findings show just how much they have been changing, perhaps worsening, in recent years.

Enjoy spring without the worry of triggering your allergies. Bru-nO/ Pixabay