While Michael Arrington revels in I told you so, deservedly, his colleague, MG Siegler, rockets to the top of the techmeme heights with his post, Google Drops A Nuclear Bomb On Microsoft. And It’s Made of Chrome:

Wow. So you know all those whispers about a Google desktop operating system that never seem to go away? You thought they might with the launch of Android, Google’s mobile OS. But they persisted. And for good reason, because it’s real.

In the second half of 2010, Google plans to launch the Google Chrome OS, an operating system designed from the ground up to run the Chrome web browser on netbooks. “It’s our attempt to re-think what operating systems should be,” Google writes tonight on its blog.

But let’s be clear on what this really is. This is Google dropping the mother of bombs on its chief rival, Microsoft.

And it’s an Open Source bomb. Say they, “We have a lot of work to do, and we’re definitely going to need a lot of help from the open source community to accomplish this vision.” The OS will basically be the Chrome browser running inside “a new windowing system on top of a Linux kernel.”

Google says the OS “will initially be targeted at netbooks.” The NYTimes:

“Speed, simplicity and security are the key aspects of Google Chrome OS,” said Sundar Pichai, vice president of product management, and Linus Upson, engineering director, in a post on a company blog. “We’re designing the OS to be fast and lightweight, to start up and get you onto the Web in a few seconds.”

Mr. Pichai and Mr. Upson said that the software would be released online later this year under an open-source license, which would allow outside programmers to modify it. Netbooks running the software will go on sale in the second half of 2010.

Giving credit where credit is due, Ars Technica had the story up about 2 hours before Google confirmed it last night. And CNet looks at the reasons Microsoft may not be dead man walking. (Not much there.)

Now everyone’s waiting to hear Microsoft’s take.