I’m at a loss. Three obvious possibilities:

(1) It’s one of ours but is being officially denied because it’s part of some secret operation. If that’s true, though, why launch it so close to the coast where people will see it and buzz about it? Alternately, if (as speculated in the first clip below) it’s a show of strength to China or Asia generally, why not do it further out in the Pacific? You’re not showing much strength if you’re firing it off in your own backyard. And in fact, one military official says that an exercise like that wouldn’t be held so close to a population center.

(2) It’s a commercial rocket. Given the size and location of the thing, though, wouldn’t we already have an idea of who the culprit was? Presumably there’s a short list of commercial entities capable of boosting a bird that big. And if it was fired from a land-based platform, surely someone had to have seen the launch preparations. So why the confusion today?

(3) It’s one of theirs. If it did come from the water and it’s really not a U.S. operation, then presumably it’s from an enemy sub. Relations with China have been souring, and they’ve made their opposition to American naval influence in Asia increasingly clear. Maybe this was a message to The One while he’s in their backyard shoring up alliances that China’s navy is stronger than thought? Wouldn’t be the first time a Chinese ship has surprised the U.S. Navy with its stealth, and Chinese advances in missile tech have been in the news of late. I don’t buy this theory either, though: Firing a missile within 35 miles of L.A., where it’s sure to be seen by the public and thus designed to embarrass the U.S. military, would be provocative in the extreme. Why now, when Hu Jintao just finished making plans to visit the White House early next year?

Danger Room is pumping its military sources hard for info but has nothing thus far, and if you watch the NBC clip below, Jim Miklaszewski sure does seem to believe that the Pentagon’s surprise about this is in earnest. All theories are welcome!

Update: Headlines comments imported.

Update: A commenter on CBS’s post claims that there was some sort of U.S. military notification issued in advance of the launch. In that case, though, why all the difficulty today getting confirmation?

Update: An awful lot of people in the know seem to think that this was indeed some type of rocket, but at least a few experts think this might be the contrail from an airplane that only looks vertical because of an optical illusion. Meanwhile, Cuffy Meigs notes that military missile tests have indeed originated from that area in the recent past — although, of course, that doesn’t explain why the Pentagon seems so baffled this morning.