On February 2, 2009 Google launched Google Earth 5.0. Among the most significant features were Historical Imagery, Touring, and 3D Mars.
" ♦ Historical Imagery: Until today, Google Earth displayed only one image of a given place at a given time. With this new feature, you can now move back and forth in time to reveal imagery from years and even decades past, revealing changes over time. Try flying south of San Francisco in Google Earth and turning on the new time slider (click the "clock" icon in the toolbar) to witness the transformation of Silicon Valley from a farming community to the tech capital of the world over the past 50 years or so.
" ♦ Touring: One of the key challenges we have faced in developing Google Earth has been making it easier for people to tell stories. People have created wonderful layers to share with the world, but they have often asked for a way to guide others through them. The Touring feature makes it simple to create an easily sharable, narrated, fly-through tour just by clicking the record button and navigating through your tour destinations.
" ♦ 3D Mars: This is the latest stop in our virtual tour of the galaxies, made possible by a collaboration with NASA. By selecting "Mars" from the toolbar in Google Earth, you can access a 3D map of the Red Planet featuring the latest high-resolution imagery, 3D terrain, and annotations showing landing sites and lots of other interesting features" (Official Google Blog, http://googleblog.blogspot.com/2009/02/dive-into-new-google-earth.html, accessed 11-29-2010).