The NASA Orbiting Carbon Observatory was intended to monitor carbon dioxide in order to help assess global warming.
Now it's hanging out with Landsat 6.
The rocket that the satellite was traveling on failed to separate from its payload fairing. The extra weight prevented the rocket from reaching orbit and the satellite plunged into the Ocean near Antartica. That's a $278 million swim.
Really though, it's all about Google Ocean now, so OCO probably just wanted a piece of the spotlight.