Amateur astronomers have spotted two fireballs lighting up Jupiter's atmosphere, the first time telescopes have caught such small events, scientists say.

The two fireballs, which caused fleeting bright spots on Jupiter that were visible through backyard telescopes, occurred June 3 and Aug. 20, a NASA release said Thursday.

A paper published in Astrophysical Journal Letters estimated the object causing the June fireball was 30 to 40 feet in diameter, comparable in size to asteroid 2010 RF12 that flew past Earth Wednesday.

The Aug. 20 object was thought to be about the same size.

"Jupiter is a big gravitational vacuum cleaner," Glenn Orton, at NASA's Jet Propulsion Laboratory in Pasadena, Calif., said. "It is clear now that relatively small objects, remnants of the formation of the solar system 4.5 billion years ago, still hit Jupiter frequently. Scientists are trying to figure out just how frequently."

This kind of discovery couldn't have been made without amateur astronomers around the world, whose observations of Jupiter provide a near round-the-clock surveillance that would be impossible to do with the long lines of scientists waiting to use the large telescopes, Orton said.