Sprinkled across the ocean floor, invisible from the surface, are hundreds, or maybe thousands of sinkholes called “blue holes”. They are as intriguing to many scientists as black holes are, and we still have a lot to learn about them.

PC: Bob Krist / Getty Images

The blue hole that has captured the most attention recently is called the ‘Green Banana’, located offshore from St. Petersburg, Florida. Next month, scientists will venture into the sinkhole, which extends around 275 feet, like an inverted, hourglass-shaped 20-story building, anchored in the ocean floor. One of the deepest blue holes ever discovered, this will be the most comprehensive study completed yet. Researchers are trying to find out if the Green Banana connects to other sinkholes and whether freshwater flows within. Being one of the deepest blue holes, everyone is excited about what it will show and tell us about life in the deep.

PC: Curt Bowen

We know that because of their unusual seawater chemistry, blue holes are typically teeming with life, and are atypically clear. However, the entry points are so narrow that it stops an automated submersible from entering – one of the reasons we know so little about them. In next month’s mission, divers will enter this deep blue hole using a 600-pound triangular shaped lander. They do not yet know what they will find, biologically and chemically from exploring the “Green Banana”…  but we’re excited to find out!

PC: NOAA