Dry Tortugas islands near Florida are featured in this image photographed by an Expedition 17 crewmember on the International Space Station. The Dry Tortugas are a group of islands located approximately 75 miles west of Key West, Florida; they form the western end of the Florida Keys in the Gulf of Mexico. Like the Keys, the Dry Tortugas are formed primarily of coral reefs over older limestone formations. The islands were named "Dry Tortugas" upon discovery by Ponce de Leon in 1513 — "tortugas" means turtles in Spanish, and the islands are "dry" as no fresh water is found on them. From the air, the islands present an atoll-like arrangement, however no central volcanic structure is present. The islands are only accessible by boat or seaplane; nevertheless they have been designated the Dry Tortugas National Park, and are visited by hundreds every year. This view highlights three islands in the group; Bush Key, Hospital Key, and Garden Key — the site of Fort Jefferson. Fort Jefferson is a Civil War era fort, perhaps most notable for being the prison of Dr. Samuel Mudd, who set the broken leg of John Wilkes Booth following Booth’s assassination of President Lincoln. The fort itself is currently undergoing extensive restoration to prevent collapse of the hexagonal outer walls (center). The islands stand out due to brown and light tan carbonate sands visible above the Gulf of Mexico water surface. Light blue-green irregular masses in the image surrounding the islands are coral reef tops visible below the water surface.
Image credit: NASA
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