FAST FACTS
Where is it? Carter's Cay and Strangers Cay, Bahamas [27.105580266, -78.06669135]
What's in the photo? Underwater sandbanks and coral reef surrounding a couple of small islands.
Who took the photo? Unnamed astronaut on the International Space Station (ISS).
When was this done? October 20, 2016
This intriguing astronaut photo shows a series of undulating sandbanks surrounding a pair of small islands in the Bahamas. The submerged eddies were formed in part by a coral reef lurking at the edge of a hidden ocean “cliff.”
This photo shows a series of complex sandbars and a shallow barrier coral reef in the waters surrounding two tiny islands, Carter's Cay (bottom left) and Strangers Cay (top right). The islands are the two northernmost land masses in the Bahamas, located approximately 125 miles (200 kilometers) east of Florida. (For context, Strangers Cay is about 2.2 miles (3.6 km) wide at its widest point.)
The sandbanks, which can be seen winding like ribbons around the two reefs, were formed by decades of consistent ocean currents, causing sand to accumulate in the same place over time.
But the coral reef that crosses the bottom right corner of the image and the waves crash against its far edge is much older and likely formed over several millennia.
The largest and most prominent sandbar, which appears as a giant U-shape in the center of the image, is directly opposite a large break in the coral reef. This is no coincidence: According to the Earth Observatory, the reef's break created a strong and prolonged tidal flow that pushed the sand much further back.
These sand eddies are quite small compared to some of the larger sand banks in the region. The biggest is Great Bahamas Bankwhich covers an area of about 80,000 square miles (210,000 square kilometers) off the Exuma Islands in the central Bahamas and supports a massive seagrass ecosystem.
These features often attract comparison with abstract paintings or Northern lightsthanks to its shape and mesmerizing glow when viewed from above. However, their supposed luminosity is actually just an optical illusion caused by their proximity to the ocean surface. In some areas, the sand is likely just 6.5 feet (2 meters) below the waves, according to the Earth Observatory.
If you look closely at the ocean surface in the image, you will also notice that the water in the upper left corner of the islands is very light and covered in shimmering streaks, while the lower right corner of the image – behind the reef – is darker and shows traditional wave patterns.
This is the result of a steep drop-off in the deep ocean just beyond a coral reef, similar to the one depicted in the movie Finding Nemo. Beyond this point, ocean currents create waves that many people see from an airplane window. But instead, the wind behind the reef turns the ocean surface into thin stripes.
It is because of this cliff that the sandbanks are not visible behind the reef.
For more incredible satellite photos and images of astronauts, check out our website. Earth from space archives.
