'Sonar Anomaly' Isn't a Shipwreck, and It's Definitely Not Aliens, NOAA Says

Rather, it's "geologic in origin," NOAA Ocean Explorer reported in a tweet yesterday (June 27).

The finding, although not surprising, is a bit of a letdown after NOAA tweeted earlier that day that the anomaly could be "an archaeology site, a geological formation or otherwise!" [Photos: Colonial-Age Shipwrecks Found Off Cape Canaveral Coast]

Scientists aboard NOAA's Okeanos Explorer noticed the anomaly while mapping the seafloor off the coast of North Carolina. They dubbed the site the "Big Dipper" anomaly and promptly sent a remotely operated vehicle (ROV) underwater to investigate.

Given that North Carolina's coast is called the "Graveyard of the Atlantic," because of the many shipwrecks discovered in the area, NOAA scientists initially speculated that the anomaly could be the remains of a long-lost ship, according to The Charlotte Observer.

But the ROV found otherwise. The anomaly turned out to be a "rocky feature," NOAA said in a tweet. On the upside, this feature "is great habitat for many species, including the many fish already seen," NOAA noted.

The Okeanos Explorer's current expedition — called Windows to the Deep 2018: Exploration of the Southeast U.S. Continental Margin— is helping NOAA researchers map the seafloor in unknown and poorly understood deepwater areas of the southeastern United States, according to the expedition's mission plan. The expedition began on May 22 and runs through July 2.

The feature discovered at the "Big Dipper" anomaly is, in fact, a rocky habitat that is home to a number of fish, crabs, anemones and coral. (Image credit: NOAA Office of Ocean Exploration and Research, Windows to the Deep 2018)

Parts of the expedition included mapping "unexplored areas of the Blake Plateau, Blake Ridge, Blake Escarpment, submarine canyons offshore of North Carolina, submerged cultural heritage sites, areas predicted to be suitable habitat for deep-sea corals and sponges, inter-canyon areas, and gas seeps," NOAA said.

Meanwhile, the ROV dives are helping scientists understand the "diversity and distribution of deepwater habitats in this region," NOAA said.

However, aliens and unknown shipwrecks don't seem to be a part of that underwater world, at least not yet.

A 3D view of the scour mark caused by a hard object on the seafloor, as mapped by the NOAA Ship Okeanos Explorer. This image shows the sonar reflection intensity ("backscatter") in black and white, which is draped over the seafloor. White indicates a strong reflection and hard surface. The depth of this feature is 1,083 feet (330 meters). Although thought to possibly be a shipwreck, the bright mound ended up being a rocky reef habitat. (Image credit: Image courtesy of the NOAA Office of Ocean Exploration and Research, Windows to the Deep 2018)

Original article on Live Science.

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Laura is the managing editor at Live Science. She also runs the archaeology section and the Life's Little Mysteries series. Her work has appeared in The New York Times, Scholastic, Popular Science and Spectrum, a site on autism research. She has won multiple awards from the Society of Professional Journalists and the Washington Newspaper Publishers Association for her reporting at a weekly newspaper near Seattle. Laura holds a bachelor's degree in English literature and psychology from Washington University in St. Louis and a master's degree in science writing from NYU.