Last July 4th, NASA's Juno spacecraft slowed its record breaking pace just enough to get caught in the pull of Jupiter's gravity. (The timing, according to NASA, was just a very patriotic coincidence.) Either way, Independence Day 2016 was the last time the Juno mission pumped its brakes. In the year since, the 66-foot solar-powered craft has given scientists more and weirder Jupiter data than they ever thought possible.
So, in honor of Juno's first year orbiting the hitherto mysterious gas giant, here's a rundown of the mission's greatest scientific hits so far.
Without a good spacecraft and mission plan, Juno never would have left orbit. The Lockheed Martin-built spacecraft itself is an engineering marvel: It has traveled further from Earth (1.7 billion miles!) than any solar-powered craft preceding it, and at speeds never before achieved by a manmade object. Juno's engineers also had to protect the craft's delicate instrumentation—which does everything from snap photos to analyze the gas giant's core—from deep space's pipe-burstingly cold temperatures, not to mention Jupiter's powerful radiation and electric field.
None of which would have been helpful if the mission design didn't allow all that fancy machinery to collect good data. Fortunately for Juno, that hasn't been an issue, even though its flight plan is unconventional in the extreme. Not only are Juno's orbits way, way lower than usual—at their lowest points, just 2,500 miles above Jupiter's famous storm clouds—unlike previous Jupiter missions, they're closely spaced to allow the craft to map the entirety of the planet. "Now that we've had such success, we can say the design is one of our greatest achievements," Scott Bolton, Juno's principal investigator told WIRED in May.
The other eccentricity of Juno's orbit is that it isn't equatorial. Instead, it skims over Jupiter's north and south poles, which no one had ever seen before because of Jupiter's very slight axial tilt. (Most planets are tipped over enough for scientists to get a look at their poles from Earth, but Jupiter is practically straight up and down.) Turns out they're stunning—shockingly blue compared to the rest of the planet's stripy orange and white, and covered in cyclones that could swallow Earth whole.
So far, Juno has only completed one close pass of Jupiter—what Juno's team calls a science orbit. And while there are still a number of them to go (12 or more, thanks to an engine glitch that actually ended up shielding the spacecraft from additional radiation damage), the results of the first have already challenged long-held scientific theories about gas giants.
Seriously: Jupiter's auroras get energized by pulling electrons out of polar regions (the opposite of how the process works on Earth); and the gas giant's atmosphere, magnetic field, and gravity field are way more mobile and variable than scientific wisdom would have suggested. It's gotten to the point where planetary scientists (including Bolton) wonder if any of their assumptions about gas giants were right.
Which doesn't mean Juno is discouraging scientists. It's the opposite, really. Juno was always meant to rewrite (or at least fill in missing bits of) planetary history. According to theories Juno hasn't yet busted, Jupiter is the planet that started it all in this solar system—its composition is essentially the same as the Sun's, except it's enriched with heavier elements like carbon and nitrogen. So, it's the Sun plus the ingredients for life soup. And while scientists and space fans will have to wait for the next few science orbits to learn what that means, with Juno's track record, whatever answers the spacecraft sends Earthward will likely be field-shaping, and unexpected. So happy first anniversary, Jupiter and Juno. We can't wait to see what science your next year together will bring.
