Cassini scientists theorize that the atomic oxygen is evidence of a collision between objects in Saturn's "E-ring," which are largely made up of ice and could have released the gas as they broke apart.

"The implication is that within 100 million years time this process would erode the entire E ring, assuming there was no replenishment," Cassini team investigator Donald Shemansky said. "It's really spectacular (to witness)."

Unless those objects are replenished in the rings, Cassini investigator Donald Shemansky said, they would slowly be "eaten away" within about 100 million years.

Shemansky cautioned that project scientists had not reached firm conclusions about the eruption and were not even certain that it came from a collision among objects in the E-ring. Other possibilities include a meteorite crashing into the ring or even an event -- such as an ice volcano - on Enceladus, one of Saturn's 31 known moons.

"Remember, we've only seen one of these so far," Shemansky said, adding that the eruption apparently occurred in late January and was picked up by Cassini's instruments.

Cassini, which settled into orbit around Saturn earlier this week after a journey of nearly seven years and 2.2 billion miles, on Friday also took its first close-up images of the surface of Titan, Saturn's largest and most intriguing moon.