San Francisco ? Google Inc. on Monday launched a new version of Google Earth that allows users to explore the oceans, view images of Mars and watch regions of the Earth change over time.

The new features mark a significant upgrade to Google Earth, a popular software program that provides access to the world’s geographical information through digital maps, satellite imagery and the company’s search tools.

Google Earth 5.0 was unveiled at the California Academy of Sciences in San Francisco, where former Vice President Al Gore and others spoke about its capacity to educate the public about global warming, ocean acidification and other threats to the planet.

“This is an extremely powerful educational tool,” said Gore, who won a Nobel Peace Prize for his work raising awareness about climate change.

More than 500 million people have downloaded Google Earth since it was launched in 2005. The software is available for free on Google’s Web site.

Google Earth users can now plunge beneath the ocean’s surface, explore three-dimensional images of the underwater terrain and view articles and videos about marine science contributed by scientists and organizations around the world.

The Historical Imagery feature lets users see archive satellite images of individual locations to see how the region has evolved over time as a result of climate change and other forces.

Brian McClendon, a 1982 Lawrence (Kan.) High School graduate, is credited with developing Google Earth and Google Street View applications.