This Independence Day, millions of Americans will look to the sky to watch dazzling fireworks. But across the country, scientists will be looking up for an entirely different reason: On July 4, NASA's Juno spacecraft will enter an orbit of Jupiter, giving us an unprecedented window into the history of our solar system's oldest planet.
Jupiter is a strange world, but Juno will make it a little more familiar. In doing so, it could give scientists valuable insight into our own origin story — and clues in the ongoing hunt for alien life.
Jupiter is a planet unlike any other. If every other planet in our solar system teamed up to form one massive monolith of a world, Jupiter would still be two and half times heavier. That incredible mass only becomes more impressive when you consider the fact that Jupiter is a gas giant: With the exception of a rocky core that may or may not exist at its very center, the planet is made entirely of gaseous and liquid elements. When a quarter of your mass comes from helium molecules, it takes a lot of space to carry any real weight. More than 1,300 Earths could fit inside it.
At that size, Jupiter comes close to being more of a sickly star than a powerful planet. In fact, scientists have found many alien stars that bear a striking resemblance to the fifth planet from the sun. Some even have raging storms like Jupiter's Great Red Spot, which has been churning in the planet's atmosphere for hundreds of years.
"Jupiter is a planet on steroids," principal investigator Scott Bolton of the Southwest Research Institute said during a June 16 press briefing. "Everything about it is extreme."
Add to these superlatives the fact that Jupiter was probably the first planet to form in our solar system — perhaps even pushing some other early comers out into space with its incredible gravity, paving the way for the planets we know today — and it's no wonder that scientists want to know more about the planet.
Enter Juno. Launched in 2011, the basketball court-sized spacecraft will be the eighth vessel to visit Jupiter but the first to probe below the gas giant's thick cloud cover, giving scientists a peek at what lies beneath. It will also make the very first passes over the planet's north and south poles. And it will do all this while surviving radiation levels and a magnetic field like no probe has seen before. Barring the sun itself, Jupiter's radiation levels are the harshest in our solar system. Over the course of its year-long primary mission, Juno will be exposed to the equivalent of over 100 million dental X-rays.
The planet is surrounded with electrons, protons and ions that zip around almost at the speed of light. Scientists believe that this hostile environment is created by a layer of liquid metallic hydrogen that sits below Jupiter's cloud cover. It's under so much pressure that it conducts electricity, when combined with Jupiter's super-quick rotation, this creates a massive magnetic field.
This field creates stunning aurorae like our Northern Lights when confronted with excited particles spewed by Jovian moon Io's volcanic activity.
"Along with the studies of Jupiter’s magnetic field, Juno will make unprecedented observations of Jupiter’s aurora, which are brighter and more dynamic than Earth’s aurora. For me, this is the most exciting part of the mission . . . to finally see, in exquisite detail, the fine structure that makes up Jupiter's aurora and to watch how they evolve with time," Steffl said.
But that magnetic field is also capable of quite literally frying any intrepid space robot that gets too close. And Juno will definitely get very close: During its 32 planned orbits of the planet, the spacecraft will get closer than any orbiter ever has — within 2,700 miles of Jupiter's cloud cover.
"It's like a spray of radiation bullets," Heidi Becker of NASA's Jet Propulsion Laboratory, who serves as Juno's radiation monitoring investigation lead, said of Jupiter's radioactive particles. Juno is encased in a "suit of armor" to protect it, she explained, including a vault that keeps its flight computer and most valuable instrument components locked up in 400 pounds of titanium.
A lot of effort went into making Juno sturdy enough to withstand Jupiter's company. But researchers are confident that it will pay off: The gas giant has a lot to tell us about the early days of our cosmic neighborhood.
"One of the primary goals of Juno is to learn the recipe of solar systems," Bolton said. "Jupiter holds a very unique position in figuring out that recipe because it was the first to form."
Jupiter looks remarkably like the sun, relatively speaking. Scientists often say that the Jovian system is like a miniature solar system of its own – its largest moons may even be habitable. But unlike the sun, it contains traces of so-called heavy elements — the ones that are only formed as stars age. These heavy elements are the stuff of life as we know it, the backbones basic lifeforms and the planets that can support them.
"Jupiter is enriched with these heavy elements compared with the sun," Bolton said. "We don't know exactly how that happened, but we know it's really important."
The birth of our sun used up most of the building blocks available in the gas and dust cloud that once filled our region of space. Jupiter took most of the leftovers, and we got the leftovers of the leftovers. Something happened between the time when the sun formed and the time when Jupiter formed that allowed it to be enriched with these valuable molecules. Figuring out what exactly Jupiter is made out of — scientists aren't even entirely sure that it has a rocky core at its center at all — and how it was built could help solve the mystery.
“It is becoming increasingly clear that the formation of Jupiter was the defining event of our solar system," Yale University astrophysicist Gregory Laughlin, who isn't part of the Juno mission team, told The Post. "The discovery of thousands of alien solar systems over the past two decades has shown us that Jupiter, with its large mass and its relatively distant circular orbit, is somewhat unusual. We may, in fact, owe the existence of Earth’s habitability to Jupiter’s sculpting influence on the Earth’s formation, and it is imperative to peel some of the mystery from our mute, strange, and gargantuan planetary neighbor.”
Laughlin refers to the theory that Jupiter — in all its hulking glory — once bullied several planets out of the solar system, making room for the rocky worlds that sit close to the sun in modern times. That's just one of many Jovian mysteries that planetary scientists hope Juno can help solve.
Juno is expected to enter Jupiter's orbit just before midnight Eastern time on July 4. Scientists should be able to confirm its success soon after.