Earth Day is tomorrow, April 22! We invite you -- and everyone else on the planet -- to take part in a worldwide celebration of Earth Day this year with the agency's #GlobalSelfie event. Five of our missions are designed to gather critical data about our home planet are launching to space this year. We're marking this big year for Earth science with a campaign called Earth Right Now, and as part of this campaign the agency is asking for your help this Earth Day. While our satellites constantly look at Earth from space, on Earth Day we're asking you to step outside and take a picture of yourself wherever you are on Earth. Then post it to social media using the hashtag #GlobalSelfie. This is an image of Earth and the moon, acquired on Oct. 3, 2007, by the HiRISE camera on our Mars Reconnaissance Orbiter. At the time the image was taken, Earth was 142 million kilometers (88 million miles) from Mars, We could image Earth and moon at full disk illumination only when they are on the opposit...