Their company blog says they were faced with the question, "If you could redesign any brand, which would it be?" Their answer was NASA, so they set out to produce "Something that on a very basic, universal level was about what NASA is and does." Here are their designs, compiled into one image by The Daily What:
Base, which produced the designed unsolicited and most likely for the publicity, explains their philosophy in the redesign:
The first thing we see in NASA's previous logos is that perennial truth that what looks futuristic today looks passe tomorrow. And of course tomorrow comes faster today than it did yesterday. We also wanted to avoid anything that would be too techy--NASA isn't about technology; it's about using technology as a vehicle for doing and going and discovering. So we went with a fairly neutral typeface that won't look immediately dated. But we also wanted to de-emphasize the name in the logo to create more of a symbol that would be universally understood. So we eclipse the name with a giant sphere, which could be Earth or any other planet. In this way, we don't get rid of the "meatball"; it's still there, you just don't see it.