Spectra collected by various observatories may help identify what the impactor was, since a large amount of water at the impact location would hint at a comet as the source. “We will also compare the observations with those collected during [Shoemaker-Levy 9] 15 years ago,” since that was a known comet, Marchis says.

Without having seen it, scientists can’t tell how large the object was. “But the impact scar we’re seeing is about the same size as one of Jupiter’s big storms, Oval BA, Fletcher told New Scientist. “That, I believe, is about the size of the Earth.”

Marchis says Jupiter may be protecting Earth from getting hit by such objects. “The solar system would have been a very dangerous place if we did not have Jupiter,” he told New Scientist. “We should thank our Giant Planet for suffering for us. Its strong gravitational field is acting like a shield protecting us from comets coming from the outer part of the solar system.”

newscientist.com