Google has puzzled the world in recent weeks with their recent UFO artwork. A series of creative UFO themed Google logos have, on now three separate occasions including yesterday (Sept 21), replaced their traditional logo on the front page of the search giant. So why is Google so interested in UFOs?

The first UFO logo was "sighted" on Sept 5. Clicking on the logo queried the search phrase "unexplained phenomenon".

Along with it Google tweeted a message to its Twitter account that when translated said: "All your O belong to us", a tribute to the cult classic Japanese game, Zero Wing.

The second UFO themed Google logo, a crop circle, appeared on September 15. Clicking the logo queried the search phrase "crop circles". Click any of the images to enlarge for full size artwork.

And the latest UFO logo showed up yesterday, Sept 21. This marks the first time that Google has ever created an artwork series.

Some early theories as to why the Google UFO craze ranged from that "Google has discovered evidence to prove UFOs" to perhaps a commercial motivation for a new product launch. Or perhaps something related to their open source Android project.

However, the speculation now ends with Google's official word. The UFO logos were a tribute to the 143rd birthday of H. G. Wells, the legendary sci-fi author of "War of the Worlds". On Google's blog it reads:

To me, the whole Google UFO craze gives you an idea of how powerful Google is at delivering information. One day if Google wanted to tell the world something all they would need to do is put a big bold message above their search box. But don't count on them announcing proof of extraterrestrials anytime soon.

Whether it's Chrome. Androids. Or UFOs. One thing is for certain: Google is obsessed with shiny metallic things.