Simple facts
Where is it? Lowry Shoals, Australia [-17.32117355, 119.26473330]
What do you see in the photo? From left to right. Imperieuse Reef, Clerke Reef, Mermaid Reef
Who took the photo? Nameless astronaut on the International Space Station
When did you take it? October 18, 2011
This impressive photo of the astronaut shows a unique chain of three atolls lined up off the coast of Australia. The oval islands were once part of a huge coral system comparable to the great barrier reefs.
The island trio constitutes the Raleigh Shoals, an unmanned Australian territory located in the Timor Sea, about 180 miles (290 km) off Western Australia. From southwest to northeast (left to right), the islands are named Imperieuse Reef, Clark Reef and Mermaid Reef.
All oval structures are atolls. It is a circle of land built from fringe coral reefs that once circumnavigated an island that had sunk under the waves. According to NASA’s Earth Observatory, these atolls are evenly spaced in near perfect straight lines that span around 60 miles (100 km) from end to end.
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Each island has a surface area of approximately 30 square miles (80 square km). Only the Imperieuse and Clerke reefs have an island of white sand, or cave, remaining on the water. Imperieuse Reef also has a lighthouse, the only permanent human structure of Rowley Shoals.
The atoll is located on one of the largest continental shelfs on the planet. About 10 million years ago, the area was home to a massive barrier reef system spanning over 1,250 miles (2,000 km), and later fell into the sea due to structural subduction.
The atoll is believed to be part of the last remnants of this lost ecosystem, along with the Ningaloo Reef, the Ashmore Islands, Scott and Seringapatam Reef, according to a survey published in February 2025.
Related: See all the best images of Earth from Space
The collective ecosystem of Rowley Shoals fell significantly in the 1970s when the island became popular with tourists and began hosting deep-sea fishing expeditions.
As a result, the area is currently protected by two marine reserves. Raleigh Shoals Marine Park includes Imperial Reef and Clark Reef. Mermaid Reef Marine Park protects Mermaid Reef and the water around it. This helped each ecosystem recover to pre-tourism levels.
Today, the atolls contain a variety of marine life, including sea turtles, coral reef sharks, and giant clams, as well as about 900 species of fish, mollusks, corals, and more, according to the Australian Atlas.
Rowley Shoals is currently listed as one of the best places to go scuba diving in Australia, outside the Great Barrier Reef, according to the Professional Association of Diving Instructors (PADI). However, the atoll diving season is limited between September and December to minimize the impact of these visitors.
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