Answer to Mystery Circles Stalked : Britons Set Up Detectors in Bid to Record Patterns in Fields

Investigators are determined to discover whether aliens, whirlwinds or practical jokers are the cause of mysterious circles that have been appearing in crops across southern England.

“Operation Blackbird,” launched Monday, involves the continuous operation of more than $1.8 million worth of heat, light and sound detectors during the next three weeks to try to record the creation of the circles.

Experts have not been able to explain the markings, which for the last decade have appeared mostly in the southern English counties of Wiltshire and Hampshire at midsummer.

“We want to show that it is not a hoax,” said David Morgenstein, a member of the investigation being run by the British Broadcasting Corp. and a Japanese television network. “Crop circles are caused by something else than young farmers turning out of the pub or little green men.”

Organizers have tried to deploy equipment over as wide an area as possible, but concede that it will be random chance if the infrared cameras and spectrum sensors record a circle being created.

The phenomena appear as a flattened section in crops, usually corn or wheat, and are very symmetrical with precise boundaries. The circles have been getting increasingly complex, some now involving bar shapes and complex loops, and can be hundreds of feet long. Ideas that the circles are caused by local pranksters have been largely rejected because there are never any signs of a tractor or person going to the location. Surrounding crop areas remain untouched.