Hello again, old friend. Next July, NASA鈥檚 Juno spacecraft will go into orbit around Jupiter. It will be the first craft to go there in over a decade, and we鈥檝e got a lot of catching up to do.
As the largest of the eight planets, Jupiter has played a crucial role in shaping the solar system. Like the sun, it is mostly made of hydrogen and helium, but sniffing out the sprinkling of other elements inside could solve the long-standing mystery of how the planets formed.
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Many spacecraft have whipped past Jupiter en route to elsewhere, but Galileo spent eight years exploring the gas giant and its moons. One big surprise was that it picked up only trace levels of water vapour. Oxygen is the third most common element in the universe, so Jupiter was expected to have a fair amount of it locked up in water, maybe even as much as 20 Earths鈥� worth.
鈥淯nderstanding Jupiter will tell us more about similar planets elsewhere in the galaxy鈥�
Now Juno, which launched in 2011, is going back for a closer look. It will look for oxygen in the atmosphere at six altitudes, and will orbit nearer the planet鈥檚 poles, giving a contrast to Galileo鈥檚 equatorial view. Any wiggles picked up by Juno鈥檚 gravity sensors will give us clues about Jupiter鈥檚 interior, which may have a solid core made from heavier elements.
These results should help us build a picture of Jupiter鈥檚 birth. A solid core would suggest it started out in a similar way to Earth, with rocks and ice slowly coming together, after which any hydrogen and helium floating around got sucked in. If not, Jupiter may have collapsed out of a much larger, amorphous gas cloud.
A soggy Jupiter would hint at aeons of cometary bombardment while the planet formed, a process that may also have filled Earth鈥檚 oceans. If Jupiter turns out to be dry, it may be that water brewed within Earth instead. And understanding our Jupiter will tell us more about the many Jupiter-like exoplanets we鈥檝e spotted elsewhere in the galaxy. You could say it鈥檚 a giant opportunity.
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(Image: NASA/JPL)
This article appeared in print under the headline 鈥淲elcome back to Jupiter鈥�
