When the Juno spacecraft arrived at Jupiter earlier this week, it carried with it three tiny passengers: Lego figurines of the Roman god Jupiter, his wife Juno, and Italian astronomer Galileo Galilei.

The three figurines were installed on the spacecraft as part of the Bricks in Space outreach program between NASA and the Lego Group. Their purpose is to encourage children’s interest in the science, technology, engineering, and mathematics fields.

Each of the figures represents humanity’s relationship with the gas planet: The figure for Jupiter, the Roman god of the sky and thunder, carries a lightning bolt, while his wife, Juno, carries a magnifying glass, representing her search for the truth. The figure for Galileo represents the scientist who discovered the Jupiter's largest moons in 1610, and carries a telescope and globe of the planet.

The figures are cast in a special space-grade aluminum

Each of the characters are the same size as your typical Lego figures, but are cast in a "special space-grade aluminum," according to Scott Bolton, Juno’s principle investigator. "They have gone through all the testing to make sure that they fit on our spacecraft in a way that is like our other science instruments."

In addition to the Lego figures, the spacecraft carries with it a plaque honoring Galileo. It features a portrait of the scientist and a passage from his notes on his discovery of the Jovian moons.

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