Google on Monday added imagery for the ocean floor to its popular 3-D mapping service Google Earth, which allows users to browse satellite images of the Earth's terrain. The new version of Google Earth also introduces Historical Imagery, a feature that enables users to virtually travel back in time through archival satellite and aerial imagery, Touring, which makes it simple to create a narrated tour in Google Earth and share it with the world and Google Mars 3D, which features hi-res imagery and terrain of the red planet.

Google executives announced the enhancements at the California Academy of Sciences in San Francisco, highlighting partners ranging from the U.S. Navy to National Geographic.

Ocean in Google Earth combines sea floor terrain and expert content to provide users with an opportunity to explore some of the most difficult-to-reach parts of the world. Virtual travelers to Hawaii, for example, can examine underwater volcanoes, see videos about the exotic marine life of the region, read about nearby shipwrecks and contribute photos and videos of favorite surf spots.

The ocean feature is on by default in the newest version of Google Earth. As users zoom in on the ocean they will see a dynamic water surface, and once they dive beneath the surface they can navigate 3D sea floor terrain. The feature includes 20 content layers, containing information contributed by the world's leading scientists, researchers, and ocean explorers (for a full list of partners visit http://earth.google.com/ocean/partners.html).

These include:

- An "Explore the Ocean" layer containing photos and videos about ocean hot spots around the world contributed by over 80 individuals and organizations

- A National Geographic Magazine geo-quiz and overlays from their new Atlas of the Ocean

- Videos from the archives of Jacques Cousteau, featuring never-before-seen footage of historic ocean expeditions

"With this latest version of Google Earth you can not only zoom into whatever part of our planet?s surface you wish to examine in closer detail, you can now dive into the world?s oceans that cover almost three-quarters of the planet and discover new wonders that had not been accessible in previous versions of this magical experience," said The Honorable Al Gore at this morning's launch event in San Francisco. "Moreover, with the new historical imagery feature, you can look back in time and see for yourself the unprecedented pace of change taking place on the Earth ? largely because of human influences. For example, you can watch the melting of the largest glacier in Glacier National Park?the Grinnell Glacier?image by image, for the last decade."

Also launched today:

Historical imagery: In previous versions of Google Earth, users could only view only one set of imagery for a given location. Now users can activate a time slider to see both newer and older satellite imagery from around the globe, enabling them to observe a single location's development over time.

Touring is a simple new way for users to create narrated tours of imagery and content in Google Earth. By simply pressing the "record" button, users can fly from place to place, zoom in or out and click on content balloons, providing voiceover narration along the way.

Google Mars 3D is the latest stop on Google's virtual tour of the galaxy. Users can travel to Mars with the click of a button and see high resolution imagery and 3D terrain. They can fly to the top of Olympus Mons, the tallest volcano in our solar system, read geo-located excerpts about different locations on the planet from A Traveler's Guide to Mars, observe where various Mars Rovers and Landers have touched down and much more.

GPS Tracking - Previously only available in the Plus and Pro versions of Google Earth, now all users can upload tracks from GPS devices (including many Garmin, Magellan, and NMEA-compatible devices) to Google Earth, making it easy to visualize and record running, hiking and biking routes.

Google Earth 5.0 is now available in 41 languages. It can be downloaded here