NASA's Juno spacecraft is orbiting the giant planet Jupiter, having survived a harrowing journey through radiation and dust to enter into orbit on Monday night. The spacecraft is technically uncrewed, but there are three passengers of sorts.

A trio of Lego figurines are aboard the spacecraft, each representing important discoveries about the largest planet in our solar system. The Lego pieces are crafted in the likeness of Galileo Galilei, who discovered four of Jupiter's moons — Europa, Io, Callisto and Ganymede — in 1610, the Roman god Jupiter and Jupiter's wife Juno.

"These [minifigures] are made by the LEGO company in a special agreement with NASA," said Scott Bolton, the mission's principal investigator, in a statement. They don't look like typical Legos, though, for good reason.

Lego figurines aboard Juno. They are made of aluminum. Image: NASA

"They're made out of spacecraft-grade aluminum," Bolton said.

According to a Lego spokeswoman, the three pieces were milled out of a single block of aluminum, which was chosen in order to allow the figures to withstand the extreme temperatures encountered during the journey.

"Another consideration was choosing a non-magnetic metal so that they wouldn’t interfere with other equipment," the spokeswoman told Mashable in an email.

The Lego pieces have set records for the fastest-traveling Legos on record. The spacecraft blasted away from Earth in 2011, and reached Jupiter five years later, on July 4.

The Lego pieces are part of a joint agreement between the Lego company and NASA that is aimed at engaging the public in science education. The space agency is encouraging the public to use Lego pieces to construct models of the future of space exploration, and submit these to NASA as part of a competition.

"We put these LEGO minifigures on board Juno in order to inspire and motivate and engage children, to have them share in the excitement of space exploration and reaching for the best goals that you can," Bolton said.

The Juno figure holds a magnifying glass to signify her search for the truth, while her husband holds a lightning bolt. Galileo holds both a model of the planet and his telescope.

These Lego pieces are not the first to explore space, however. In 2011, for example, astronauts aboard the International Space Station played with sets of their own.

