"Asteroid" WalkerToday a NASA crew is landing on an "asteroid"—about 60 feet (18 meters) under the sea.In reality, members of the space agency's NEEMO 15 mission will test ways humans might one day visit asteroids by spending 13 days at an underwater laboratory in the Florida Keys National Marine Sanctuary.Divers—including the one above using an anchored tether—have been preparing for the mission for months at the Aquarius Reef Base, a NOAA-owned site 3.5 miles (5.6 kilometers) off Key Largo (map).Since 2001 crews with NEEMO (for NASA Extreme Environment Mission Operations) have completed 14 missions at Aquarius, mostly training astronauts for work on space shuttles and the International Space Station. The mission starting today is only the second that was primarily designed to test new equipment and operational concepts for deeper space exploration.Specifically, NEEMO 15 aims to help astronauts figure out how to move around on and collect samples from near-Earth asteroids, many of which are relatively small compared with the moon or Mars and so would have almost zero gravity.The project doesn't aim to test the actual anchors asteroid-walkers might use, since that technology is still in early stages of development. Instead, NEEMO 15 will evaluate different anchoring setups and how well people interact with them.The "sea floor itself is being used in most cases to represent the surface of an asteroid," Steve Chappell, the deputy mission manager for NEEMO 15, said via email. In some places, fiberglass "rock walls" stand in for harder surfaces.—Victoria Jaggard

Photograph courtesy NASA