A megacryometeor has left a large crater in the middle of a garden in Busby, Renfrewshire, Scotland on September 26, 2017.

The object hit several meters from the house owned by the Helliwell family, leaving a 1.4 m (4.6 feet) x 1.2 (3.9 feet) crater.

"I was sitting at my desk and heard this big boom. I thought it was an explosion and I felt the house shake. When I went downstairs the dog was acting strangely. I looked out of the window and saw a hole with white stuff in it. It was splashed all over the grass. I went out and touched it and realized it was ice," said their family friend who was at the Helliwell's home at the time of the event, the Daily Mail reported.

"If anybody had been out in the garden, it could have killed them. We just don't know where it came from. It's a complete mystery," she added.

A megacryometeor is a very large chunk of ice which, despite sharing many textural, hydrochemical and isotopic features detected in large hailstones, is formed under unusual atmospheric conditions which clearly differ from those of the cumulonimbus cloud scenario (i.e. clear-sky conditions).

The research into cryometeors was pioneered by Jesús Martínez-Frías, a planetary geologist and astrobiologist at Institute of Geosciences (IGEO) in the Spanish National Research Council (CSIC) in Madrid, in January 2000 after ice chunks weighing up to 3 kg (6.6 pounds) rained on Spain out of cloudless skies for ten days.

Although officials will usually explain these phenomena in relation to a passing aircraft, megacryometeors have been reported as far back as 1849 and before the existence of aircraft.

The heaviest known so far had more than 50 kg (110 pounds). It fell down in Brazil.

Featured image: Megacryometeor hits a garden in Scotland on September 26, 2017. Credit: Lyndsey Helliwell