Google regularly celebrates people or events from the past with a special logo, but it sometimes celebrates current events too, either organized ones like the Olympics, or less organized ones like asteroids flying close to the Earth.
It's no surprise that Google had an asteroid 2012 DA14 doodle ready for today. It's also no surprise that Google pulled it, since another space rock happened to come close to Earth today, too close in fact.
Out of respect for those injured by the meteor that disintegrated over Russian this morning, Google removed the asteroid logo it had prepared, but only after it ran for a short while.
You can still check out the doodle if you want, Google is still hosting it, it shows the 'g' letter from the Google logo getting out of the way of the asteroid, a bit too close to reality unfortunately.