......" "We've now seen 11 and possibly 12 lunar impacts since we started monitoring the Moon one year ago," said Bill Cooke, head of NASA's Meteoroid Environment Office. "That's about four times more hits than our computer models predicted."

So their computer models were off by a factor of 4.

Considering that Earth gets hit by impactors which are about a ton or more at a rate of about 30 times per year, 11- 12 impactors on one side of the Moon should have been easily predictable. It seems to me that if they do a better job at detection that could see more than 12 impactor hit the moon per year.

"Most meteoroids that enter Earth's atmosphere burn up harmlessly. The bulk of shooting stars are caused by stuff no bigger than sand grains and a few pea-sized objects. But even something as big as a basketball will usually burn up, in a spectacular fireball, before hitting Earth's surface."

Perhaps this explanation points to a possible reason their computer model were off by so much. Instead of a basketball sized object- it's an objects up to the size of a car that will usually burn up in Earth's atmosphere and cause spectacular fireballs. And though it's "common knowledge" that "stuff no bigger than sand grains and a few pea-sized objects" cause shooting stars, this is probably wrong. It seems to me it's more reasonable that pea size or golf ball size to basketball size objects can make enough light to see from a distance of tens of miles that make a streak of light miles in length.