A mouse over of the logo says ‘Birthday of H.G. Wells’.
H.G. Wells, the father of Sci-Fi (screw you Jules Verne) was born September 21st, 1866.
According to www.telegraph.co.uk, Google has been hinting at the fact the the UFO themed logos were building up to celebrate the writers birthday. Earlier, Twitter messages gave the coordinates 51.327629, -0.5616088: the location of Horsell Common, near Woking in Surrey. Horsell Common was the site of the first Martian landing in the 1898 sci-fi classic The War Of The Worlds.
On Google’s official blog, they stated “we wanted to celebrate H.G. Wells as an author who encouraged fantastical thinking about what is possible, on this planet and beyond.”
Google’s changes the theme of its logo often, featuring popular events and sometimes hinting at upcoming releases.
While not confirmed, its said the previous logo was a nod toward Zero Wing, a video game where the phrase “All your base are belong to us” comes from. Evidence for this comes from a Google Tweet ‘1.12.12 22.214.171.124 15 1.18.5 126.96.36.199.14.7 20.15 21.19’ which decodes to ‘All Your O are belong to us’