Internet users were momentarily alarmed yesterday when they learned a 10-mile-wide asteroid was on a direct collision course with Earth. The news came via CNN's iReport, a site featuring user-generated content that is supposed to be moderated and fact-checked by CNN editors.

The story claimed astronomers at NASA slated the asteroid's arrival date for March 35, 2041 -- but failed to explain how March was granted four extra dates. NASA eventually confirmed the claim as nonsense, but the story remained live for 24 hours before it was finally taken down.

"Astronomers have placed the odds of an impact at 1 in 2.04," the report claimed, "which is by far the most unprecedented risk ever faced to humanity, let alone from asteroids. Such an impact could potentially end civilization as we know it."

In a statement explaining the retraction, CNN wrote: "NASA has confirmed via email that this story is false. A spokeswoman for the Jet Propulsion Laboratory says that the largest object detected by NEOWISE measures 3 km in diameter and poses no risk to Earth."

NEOWISE is the NASA mission aimed at finding and observing near-Earth objects. Although NASA is rather adept at locating the largest flying rocks in nearby space, in recent years the agency has been recruiting citizen scientists to help its astronomers find less obvious asteroids -- an effort hastened by last year's Chelyabinsk meteor, which exploded over Russia.