Google Earth 6 offers new perspectives on oceans, time, and Mars

Google Earth 6, the ultimate geo-mashup, stitches together data from echo soundings, satellite imagery, and radar to reveal contours of the ocean floor, Mars, and of course, Earth.

Canyons and valleys rise and fall in Google's newest model of the sea based primarily on two kinds of data: soundings, which are made by ships bouncing sound off the ocean's floor, and radar readings measuring sea levels, which rise above underwater mountains and other high ground. Overlaid are new data layers showing everything from pinpointed shipwrecks (linked to YouTube videos) to the live whereabouts of tracked whales and sharks. 

New custom tours are easy to create by importing GPS data or by simply recording your actions in Google Earth, creating a custom KML file containing geographic data and imagery that's easy to share online. The new tours can even dive underwater.

Historic views, dating back to the 1940s in some cases, illustrate striking landscape changes by bringing together a patchwork of high-resolution aerial imagery culled from government and private archives. Similarly, new views of Mars were stitched-together images from NASA's rovers, orbiters, and the European Space Agency spacecraft.

The 400 megabyte installation is hefty but straightforward. For the armchair explorer, it's a great way to see the world for free.

--Michael Fitzhugh, tech writer