To mark this year's Earth Day, the National Aeronautics and Space Administration is encouraging as many people as possible to participate in its #Global Selfie event April 22.

A NASA news release explains the space agency seeks to build a unique image "from the ground up ... We wanted to create a different picture of our planet -- a crowd-sourced collection of snapshots of the people of Earth"

That said, NASA is asking members of the public "to step outside and take a picture of yourself wherever you are on Earth. Then post it to social media using the hashtag #GlobalSelfie."

Once those pictures stream around the world on Earth Day, the individual pictures tagged #GlobalSelfie will be used to create a mosaic image of Earth -- a new "Blue Marble" built bit by bit with your photos.

As far as the content of the pictures, NASA says the sky's the limit.

"Get outside and show us mountains, parks, the sky, rivers, lakes -- wherever you are, there's your picture. Tell us where you are in a sign, words written in the sand, spelled out with rocks" or by using one of the printable signs available for download at the NASA Website, said the release.

The Earth mosaic image and a video comprising the anticipated images will be put together and released in May.

The year 2014 is a big one for NASA's efforts to study the earth itself, with five missions designed to gather data about Earth launching later this year.

NASA already studies Earth's atmosphere, land and oceans with 17 missions currently orbiting the planet.

This satellite data helps NASA scientists piece together a clear picture scientifically.

NASA said it will be monitoring photos posted to five social media sites: Twitter, Instagram, Facebook, Google+ and Flickr.

Participants can post their photos to Twitter, Instagram or Google+ using the hashtag #GlobalSelfie. They can otherwise upload photos to the #GlobalSelfie event page on Facebook or the #GlobalSelfie group on Flickr.

Visitors also have the opportunity to join the #GlobalSelfie Google+ event page.