Juno's principal goal is to understand the origin and evolution of Jupiter. Underneath its dense cloud cover, Jupiter safeguards secrets to the fundamental processes and conditions that governed our solar system during its formation. As our primary example of a giant planet, Jupiter can also provide critical knowledge for understanding the planetary systems being discovered around other stars.
With its suite of science instruments, Juno will investigate the existence of a solid planetary core, map Jupiter's intense magnetic field, measure the amount of water and ammonia in the deep atmosphere, and observe the planet's auroras.
Juno will let us take a giant step forward in our understanding of how giant planets form and the role these titans played in putting together the rest of the solar system.
When you see photos of Jupiter, they're almost always the of same view: the north pole at the top, the gaseous bands perfectly horizontal, and the Red Spot somewhere in the mix. But @robdubbin reminds us that there are other ways of looking at Jupiter. Here's a view of the planet's southern hemisphere:
This image was tweeted out by the NASA Europa Mission account the other day:
One of these images is of Europa, Jupiter's icy moon, and the other eight are frying pans. Can you pick Europa out? Hint: frying pans tend not to have impact craters.
Update: The photos of the frying pans were taken by Christopher Jonassen, whose work I featured back in 2011 (which I had totally forgotten about). At the time, I even joked about the pans looking like a Jovian moon. kottke.org is a flat circle. (thx, tony)
Historic observations as far back as the late 1800s  gauged this turbulent spot to span about 41 000 kilometres at its widest point -- wide enough to fit three Earths comfortably side by side. In 1979 and 1980 the NASA Voyager fly-bys measured the spot at a shrunken 23 335 kilometres across. Now, Hubble has spied this feature to be smaller than ever before.
"Recent Hubble Space Telescope observations confirm that the spot is now just under 16 500 kilometres across, the smallest diameter we've ever measured," said Amy Simon of NASA's Goddard Space Flight Center in Maryland, USA.
Amateur observations starting in 2012 revealed a noticeable increase in the spot's shrinkage rate. The spot's "waistline" is getting smaller by just under 1000 kilometres per year. The cause of this shrinkage is not yet known.
Clive Thompson recently saw the moons of Jupiter with his own eyes and has a moment.
I saw one huge, bright dot, with three other tiny pinpoints of light nearby, all lined up in a row (just like the image at the top of this story). Holy moses, I realized; that's no star. That's Jupiter! And those are the moons of Jupiter!
I'm a science journalist and a space buff, and I grew up oohing and aahing over the pictures of Jupiter sent back by various NASA space probes. But I'd never owned a telescope, and never done much stargazing other than looking up in the night unaided. In my 45 years I'd never directly observed Jupiter and its moons myself.
So I freaked out. In a good way! It was a curiously intense existential moment.
For my birthday when I was seven or eight, my dad bought me a telescope. (It was a Jason telescope; didn't everyone have a telescope named after them?) We lived in the country in the middle of nowhere where it was nice and dark, so over the next few years, we looked at all sorts of celestial objects through that telescope. Craters on the Moon, the moons of Jupiter, Mars, and even sunspots on the Sun with the aid of some filters. But the thing that really got me, that provided me with my own version of Thompson's "curiously intense existential moment", was seeing the rings of Saturn through a telescope.
We had heard from PBS's Jack Horkheimer, the Star Hustler, that Saturn and its rings would be visible and he showed pictures of what it would look like, something like this:
But seeing that with your own eyes through a telescope was a different thing entirely. Those tiny blurry rings, visible from millions of miles away. What a thrill! It's one of my favorite memories.
He used the accelerometer on an Android phone to measure the G force.
The centrifuge is a genuinely terrifying device. The lights dim when it is switched on. A strong wind is produced as the centrifuge induces a cyclone in the room. The smell of boiling insulation emanates from the overloaded 25 amp cables. If not perfectly adjusted and lubricated, it will shred the teeth off solid brass gears in under a second. Runs were conducted from the relative safety of the next room while peeking through a crack in the door.