On August 4, NASA successfully launched its Juno probe, meant to explore Jupiter, the largest and most massive planet in the solar system. While shooting probes into space is just another day at NASA, this time the probe is carrying some unusual passengers: three Lego minifigures.

All three figures have a history with Jupiter. One of them is made to resemble Jupiter himself, the Roman thunder god that inspired the naming of the planet. Another is Juno, the sister (and wife… ick) of Jupiter, and obviously who the probe is named after. The last is a mini Galileo, the legendary astronomer who first observed Jupiter’s moons. Galileo was also the name of the last probe NASA sent to explore Jupiter, which arrived there in 1995.

Lego made the minifigs especially for the Juno mission. Unlike the usual plastic toys Lego makes, these figures are made of aluminium, making them hardy enough to withstand the extreme conditions of space flight. Besides enduring the intense force of escaping Earth, the minifigs will ride with Juno as it slingshots around planets to achieve fantastic speeds to reach Jupiter by 2016. They’ll also be subject to the extreme cold of outer space.

NASA  headed to the big planet Jupiter, looking for the clues to help answer pressing questions about the early days of the solar system.

“Jupiter holds the history of the solar system,” said Scott Bolton, director of the space science department at the Southwest Research Institute in San Antonio, and the principal investigator for the Juno mission. “If you want to understand that first step of how you went from forming a sun to forming the planets, you have to understand what went into Jupiter and how it was made.”

“There’s a missing piece that turns out to be important,” Dr. Bolton said.

“Life is in the balance here,” Dr. Bolton said, “and the things that make us up — that everything we’re looking at, breathing, touching — is all more or less unexplained.”

There are a few reasons that Jupiter holds particular interest for scientists. For one thing, it probably formed first, before the other planets. And its gravity is so strong that once anything got sucked into it during those formative years, it never got out again.

Even before the Galileo mission, astronomers had measurements indicating that Jupiter contained higher concentrations of heavier elements than the Sun — a surprising finding, because both bodies were formed out of the same hydrogen cloud. But they came up with a plausible explanation: Among the solar system leftovers, they speculated, were water ice crystals. After all, hydrogen is the most common element in the universe, oxygen is third and water molecules — two hydrogens and one oxygen — should be common. Ice traps heavier elements, and thus the icy bits that gathered into what became Jupiter could have skewed the concentrations higher.

The Galileo probe did measure enhanced concentrations, as expected, but not in the pattern predicted by the ice explanation. “In fact, in that one measurement, all the theories of how planets were made were proven wrong,” Dr. Bolton said, “and we were like, ‘Oh no, what now?’ Nature threw us a curveball.”

Juno is taking a different approach. The heat of Jupiter emits microwaves, and water absorbs microwaves. By simply measuring the strength of the microwaves radiating from Jupiter, scientists will be able to figure out how much water is in the clouds.

“Once we get all those ingredients, we’ll see if we can figure out how to bake the cake, so to speak,” Dr. Bolton said.

To make the measurements, Juno will travel along a squashed elliptical orbit, swooping to within 3,100 miles of the cloud tops. Over the course of 33 orbits during the mission, Juno will get a global view of the interior. Unlike Galileo’s orbit, Juno’s will pass over Jupiter’s north and south poles, allowing the first close-up looks at the bright auroras there.

To survive the intense radiation around Jupiter, its instruments are housed inside a titanium vault. Eventually, the radiation will destroy the electronics and the craft will be sent crashing into the planet.

The gravity and magnetic field measurements could provide evidence of metallic hydrogen — at the crushing pressures inside Jupiter, hydrogen is expected turn into a liquid metal — and a core of heavier elements.

 Juno is the second in Nasa’s so called New Frontiers class missions. The first, New Horizons, was launched towards dwarf planet Pluto in 2006 and should arrive at its target in 2015.

Related posts:

1. Water found on Mars.. Is their life on Mars?
2. New findings support prospect of life on Jupiter’s moon Europa