— Fifty years after an astronaut's photo of our home planet gave rise to the first celebration of Earth Day, NASA has turned to another medium to "piece together" a planetary formation challenge.

NASA and LEGO announced the toy company's new "Build a Planet" activity on Wednesday (April 22), the 50th annual Earth Day. Launched as part of NASA's "Earth Day at Home" programming and The LEGO Group's #LetsBuildTogether initiative, the Build a Planet one-day challenge is aimed at highlighting the space agency's role in studying and preserving Earth while helping families to celebrate Earth Day while at home and apart in response to the coronavirus pandemic.

"The LEGO Group is celebrating the 50th anniversary of Earth Day by asking builders to think globally," the company said in a statement. "This Earth Day, in collaboration with our partners at NASA, we want to remind LEGO fans of all ages that space exploration is a vital component of appreciating and protecting our global home!"

Sharing images of several planets assembled from its toy bricks — including one modeled after Earth, LEGO promoted the challenge on its social media accounts.

"Blast off! Today's challenge is to Build A Planet... Earth, or beyond!" wrote LEGO on its Twitter, Facebook and Instagram channels on Wednesday. "Humanity's journey beyond Earth has allowed us to better understand our own planet. This knowledge will help shape future exploration of new places in our solar system too!"

Continuing a week of #LetsBuildTogether challenges each with a different theme, the LEGO Build A Planet activity promotes learning through play at home. Families are encouraged to share their planetary creations online.

"Earthlings, assemble!" NASA posted to its social media channels. "Share your creations using [the hashtags] #LetsBuildTogether and #EarthDayAtHome so we can see your masterpieces!"

NASA planned to engage with some of the builders sharing planets online by providing more information about the real destinations that the brick-built worlds represent. In addition to the planets in our own solar system, the space agency was also ready to share details about the exoplanets found in orbit around stars other than our sun.

"During my stay here on the ISS [International Space Station], one of my favorite activities was to look out of the window admire our beautiful home planet, taking a moment to appreciate the extraordinary diversity of ecosystems and life in Earth's cradle," NASA astronaut Jessica Meir said in video message recorded before she departed the space station to return to Earth on Friday (April 17).

"As NASA returns humans to the moon and eventually beyond, views of our home planet from these space explorers will continue to amaze and inspire the world," she said.

The first Earth Day was celebrated in 1970 based on the inspiration and change of perspective provided by a photograph of Earth as seen from the moon.

"The iconic [1968] Apollo 8 Earthrise photo of Earth appearing over the moon's horizon helped unite a generation into appreciating the fragility of the Earth," said Meir in her Earth Day video.

Apollo 8 astronaut Bill Anders, who is credited with taking the famous photo of Earthrise, reflected on his mission and said, "We came all this way to explore the Moon, and the most important thing is that we discovered the Earth."

The Earth Day Build A Planet challenge continues the partnership between NASA and LEGO that has included astronauts assembling LEGO kits on the International Space Station and LEGO minifigures being launched to Jupiter on board NASA's Juno probe. The 2019 LEGO City Mars Exploration sets were based on NASA's own designs for extending humanity beyond low Earth orbit to the moon and Mars.