Google has finally integrated Mars and Moon imagery right in to the Google Maps web app, which enables users to explore the Mars and the Moon along with the Earth. Google already provides separate tools to explore Mars and Moon imagery, but the new addition combines all the three heavenly bodies in to the Google Maps.
To explore Mars and Moon on Google Maps, turn on the ‘Earth’ mode by clicking on the switch button at the bottom left of Google Maps. This option is available only on supported browsers and platforms.
Once in ‘Earth’ mode, zoom out completely until the entire globe is visible as shown in the above screenshot (see larger screenshot here). Now open the ‘Explore’ panel which would have switcher for the three heavenly bodies. The following video by Google Maps team demonstrates this process: