NASA’s Juno spacecraft is about to make a terrifying plunge into orbit around Jupiter later tonight — one that involves passing through a terrifying hellscape of powerful radiation. Jupiter’s massive magnetic field, known as its magnetosphere, traps charged particles around the planet, creating huge radiation belts that can fry spacecraft that pass by. These high-energy particles get accelerated to near the speed of light and can rip through an unprepared vehicle, shredding its inner atoms apart.
Sounds like a pretty scary place, right? Well if that wasn’t nightmarish enough, it turns out there’s another major hazard facing Juno on its way into Jupiter’s orbit: debris.
Just one piece of dust from these rings could muck everything up
Surrounding Jupiter are rings of debris, comprised of dust and small meteorites, that could pose a problem for Juno. These rings extend out just past the more intense parts of Jupiter’s radiation belts, according to Scott Bolton, Juno’s principal investigator at NASA. The issue is the space agency doesn’t know too much more about this debris field. NASA thinks that the rings may extend vertically, but as far as their size and exact particle density, the space agency isn’t quite sure. NASA knows about particle distribution in some areas of the rings, and the space agency has modeled the distribution for areas that it cannot see. But there is still a chance Juno might hit something. "Juno has to pass through these rings, but we do not know how close to the planet they actually go," said Bolton at a NASA press conference today.
And just one piece of dust from these rings could muck everything up. To get into its intended orbit, Juno will have to turn on its main engine for up to 35 minutes. That will slow the spacecraft down enough so that it can be captured by Jupiter’s gravitational pull. But Juno is going to be particularly vulnerable during its orbit insertion because its engine doors will be open with the engine nozzle facing forward toward the debris ring.
Jupiter's rings as seen from the Galileo spacecraft. (NASA)
Plus the probe will be moving faster than any other human-made object has gone before. So if a piece of rock or dust were to hit the open engine nozzle, it could rip a hole through the nozzle’s protective coating and stop the engine burn that’s supposed to put Juno into orbit, according to Bolton. And if the engine burn is stopped too soon, the spacecraft could blow right past Jupiter. "So that’s one of the big gambles. [We’ve] done everything we can, we protected everything we can as best we can, we modeled it, but we’re going into unknown territory," said Bolton. Later he added that the chances of Juno hitting debris isn't too high. "We believe the probability is pretty low that we're going to hit one, but it's not zero."
The probe will be moving faster than any other human-made object has gone before
The good news is Juno is one of the hardiest spacecraft out there. It’s built a bit like a tank, with a 500-pound titanium "radiation vault" surrounding the vehicle’s precious electronics. That will help shield the spacecraft from the high-speed particles in the radiation belts and hopefully any rampant debris. Also, Juno will be following a specialized polar orbit that avoids the strongest parts of the radiation belts.
But the Juno mission team is feeling both excited and cautious about Juno’s orbit insertion, which will occur later tonight. "The team, as you would imagine, is incredibly excited with anticipation mixed with the incredible tension of the reality of what we face," said Bolton. "I can assure you that every technical aspect of human ingenuity has gone into this to figure out how we can conquer Jupiter today." But he noted he won’t be truly relieved until Juno clears the more intense regions of radiation and debris around Jupiter and is pointing toward the Sun again, allowing its solar panels to get some much needed sunlight. That moment won’t come until around 12:30AM ET, more than an hour after Juno turns on its main engine at 11:18PM.
That means we’re in for a long and exciting orbital insertion tonight. But if Juno makes it into orbit, we can start to study Jupiter in more detail than ever before.