NASA has unveiled a giant global "selfie," created as a mosaic by using photographs people took in response to an Earth Day question from the space agency, "Where are you on Earth right now?"

Around 36,000 selfies submitted to NASA were chosen to be stitched together to create a 3.2 gigapixel image suggesting what the Earth might have looked like to an observer in space on April 22, Earth Day.

In response to the Earth Day request, more than 50,000 people chose to step outdoors, snap a selfie and share it world-wide using social media.

Those selfies, tagged as #GlobalSelfie, flooded into NASA from 113 countries on every continent around the globe, including Antarctica.

Photos were submitted through Facebook, Twitter, Instagram, Flickr and Google+.

NASA then stitched the thousands of images into what it termed "a new 'Blue Marble' built bit by bit with your photos."

"We were overwhelmed to see people participate from so many countries," Peg Luce, deputy director of NASA's Earth Science Division, said in a statement. "We're very grateful that people took the time to celebrate our home planet together, and we look forward to everyone doing their part to be good stewards of our precious Earth."

The website GigaPan is hosting the zoomable mosaic, and visitors can view it as a complete globe or can zoom in down to the level of individual users' selfies.

The mosaic was applied to two hemispheres of imagery captured by the instruments aboard the Suomi NPP satellite, a joint space mission between the National Oceanic and Atmospheric Administration and NASA.

The satellite's mission is to gather information on both short-term weather and longer-term climate change.

Collecting and curating the submitted images to create a global selfie took several weeks, scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, said.

Combing the satellite data with people's selfies provided a new and unique look at our planet and the people who inhabit it, NASA officials said.

"With the Global Selfie, NASA used crowd-sourced digital imagery to illustrate a different aspect of Earth than has been measured from satellites for decades: a mosaic of faces from around the globe," Luce said.