Google Earth 5.0 is a fun and free way to waste time, and now it's even better with the updated Mars in Google Earth, a 3D mapping tool that lets astronomy buffs and armchair astronauts roam the Red Planet.

You now can view antique maps of Mars from over a century ago, as well as the latest images from today's Mars spacecraft. In addition, you can go on virtual flybys with NASA's Mars Odyssey and Mars Reconnaissance Orbiter, and get guided tours of the planet from Public Radio's Ira Flatow and Bill Nye, the Science Guy.

For a quick tutorial of the new Mars in Google Earth features, check out this Google overview . Below is a brief summary of the highlights:

To travel to the Red Planet, go to the top toolbar and click "Mars."

This flies you to the Mars, where you can explore current maps or travel back in time to see antique maps by astronomers Giovanni Schiaparelli, Percival Lowell, and others:

For a present-day look at Mars, select images from a variety of modern spacecraft, including the Phoenix and Beagle2 landers and the Opportunity and Spirit rovers:

Conspiracy buffs will want to try the zoom tool. It's great for exploring mysterious imagery like the Face on Mars:

A guided audio tour helps you find your way around the planet. You can pause the tour to explore areas of interest like the Valles Marineris, a vast system of canyons that's 1860 miles long:

You can even see satellite images being taken by the NASA THEMIS camera onboard the Mars Odyssey spacecraft.

Mars in Google Earth is a lot of fun! (Sorry, no GPS navigation yet for the Red Planet.)