Ever since humans looked up at the night sky and noticed that some of the points of light moved, they have been aware of the planet Jupiter.
However, it was the invention of the telescope that let us know just how amazing Jupiter was.
Since then, we’ve sent eight probes to the planet to help us unlock its secrets.
Learn more about Jupiter, the largest planet in the Solar System, on this episode of Everything Everywhere Daily.
Jupiter is the fifth planet from the sun. It is located an average of 5.2 astronomical units away from the sun, with an astronomical unit being the average distance from the Earth to the sun.
It orbits the sun once every 11.8 years and a day on Jupiter is only 11 hours.
The planet gets its name from the Roman of the same name, who is the chief Roman deity.
It is the fourth brightest thing in the sky as seen from Earth after the sun, the moon, and Venus.
However, these fun facts about Jupiter really aren’t what makes this planet special.
Probably the single most important fact about Jupiter is the fact that it is two and a half times the mass of all other planets in the solar system combined.
Jupiter is huge. Some have called it a failed star, even though to be honest it is actually 75 times too small to start nuclear fusion. It would be more accurately called a failed brown dwarf, which is a star that fails to ignite.
The cutoff for a brown dwarf is still about 13 times the mass of Jupiter.
Because of its mass, Jupiter was probably the first planet in the solar system to form. It is believed to have started with a large rocky core, and then via gravitational attraction gathered up much of the gasses in its orbital zone.
One theory of Jupiter’s creation is known as the Grand Tack Hypothesis which suggests Jupiter might have formed at about 3.5 AU, and migrated inward to about 1.5 AU until finally moving to its current location at 5.2 AU.
Along the way, it might have been responsible for the destruction, collision, and creation of smaller rocky planets closer to the sun, including Earth.
This migration of Jupiter might explain where it picked up so much of its mass.
In a roundabout way, some astrophysicists think that Jupiter might have helped in the rise of life on Earth?
If you are wondering how a planet so far away might have influenced life on Earth, it is actually pretty simple: asteroids.
Jupiter’s huge gravity well probably meant that it sucked up an enormous amount of debris that was floating around the solar system. Debris that could have hit the Earth at some point.
This was illustrated by the 1994 impact of the Shoemaker-Levy comet into Jupiter. The impact of the comet was able to be observed from terrestrial telescopes as well as from the Hubble Space Telescope.
However, this has been hotly contested as other astrophysicists think that Jupiter is just as likely to gravitationally fling a comet in the direction of Earth.
These two theories aren’t necessarily contradictory. While Jupiter might occasionally toss something in our direction, most of the objects it influences probably wouldn’t go in the direction of Earth.
Jupiter is a gas giant, which means that there is no solid surface to the planet.
The composition of the planet is about 89% hydrogen and 10% helium, with the remaining 1% consisting of ammonia, methane, water, and other trace gasses.
The composition of the core of Jupiter is unknown, but there are many theories of what it might be. These include an exotic form of metallic hydrogen as well as possibly a supercritical fluid, which is a state where hydrogen is neither a liquid nor a gas.
The pressures are so great that some have hypothesized that it could rain diamonds deep inside Jupiter.
If you look at an image of Jupiter, one of the first things you’ll notice are the bands of clouds that surround the planet. These clouds are the very top layer of the atmosphere and they are mostly made up of ammonia crystals, as well as sulfur, phosphorus, and carbon.
Jupiter has an active weather system. The lighter-colored regions are called zones, and the darker regions are called belts.
By far, the most prominent feature on Jupiter is the Great Red Spot. The Great Red Spot is really just a massive, persistent storm. The spot rotates counterclockwise about once every six days.
We aren’t sure exactly how old it is, but it at least dates back to 1813, when it was first definitively observed. However, there were cruder observations made in 1665 which also show some sort of spot which might have been the Great Red Spot.
The Great Red Spot is believed to be a temporary feature on the planet. In just the last few years it has shrunk in size and it is entirely probable that at some point in the future it might disappear entirely.
At its maximum extent, the Great Red Spot was larger than the Earth.
One of the things that no one knew about Jupiter until we sent probes to the planet was the presence of six cyclones, evenly spaced, which were located at the South Pole.
Jupiter has the strongest magnetosphere of any planet in the solar system, which is 20,000 times more powerful than the Earth’s. This results in very powerful auroras around the north pole and weaker auroras around the south pole.
Jupiter doesn’t just get a lot of interest for the planet itself. As a gas giant, we can never really land on it. However, Jupiter is also home to its own mini-solar system of bodies that orbit it.
Jupiter has a total of 79 moons, the most of any planet by a large margin. Most of these are pretty small rocks, however, Jupiter also is home to four of the largest moons in the solar system, known as the Galilean moons:
The Galilean moons were literally discovered by Galileo and were one of the first things he discovered when turning his telescope to Jupiter. He managed to track the movement of the moons around the planet. You can see the Galilean moons yourself with any halfway decent telescope or even a very good pair of binoculars.
The largest moon is Ganymede. It is the largest moon in the solar system and it is bigger than the planet Mercury. It has a solid core, probably made of iron, and it is surface is water ice. It is the only moon in the solar system with its own magnetosphere. There might actually be a liquid ocean under the ice with more liquid water than Earth.
The second-largest moon is Calisto. It is 99% of the diameter of Mercury, but only ? of its mass. It is a mixture of rock and ice, and it also might have a liquid ocean over 100 kilometers under the surface.
The third-largest moon and the one that is closest to Jupiter is Io. Io might be the oddest body in the solar system. It has the least amount of water of any body in the solar system. It is also the most geologically active body in the solar system as well. There are over 400 active volcanoes on Io, and have even been images captured by probes of eruptions being caught in the act.
The surface of Io is mostly sulfur which is responsible for its yellowish color and the eruptions are caused by the extreme tidal forces of Jupiter and the other moons.
The smallest of the Galilean moons is Europa. It is slightly smaller than the Earth’s moon and it too has a rocky core and a water-ice crust. It is the smoothest object in the solar system, which might be caused by plumes of water vapor that have been observed.
It too may harbor a liquid ocean under the surface, and many planetary scientists think that it might be the best place in the solar system, outside of Earth, to look for evidence of life.
While it is not easily visible, Jupiter does actually have a very faint ring system around the planet.
As soon as we had the capability to send interplanetary probes, Jupiter became one of the highest priority destinations to visit.
The very first probes to send back images were Pioneer 10 in 1973 and Pioneer 11 in 1974.
Voyagers 1 and 2 flew by in 1979 on their grand tour of the gas giants.
Jupiter has also been used for gravitational assists on other probes which were going elsewhere, including the Ulysses mission to the sun, the Cassini mission to Saturn, and the New Horizons mission to Pluto.
There have been two missions that were sent purposely to Jupiter and were put into a jovian orbit. The Galileo mission, which arrived in 1995, and the Juno mission, which arrived in 2016.
Galileo actually had a probe that was dropped into the Jovian atmosphere and returned data for almost an hour.
The Juno mission is still active and it has been extended until 2025.
Future missions to Jupiter are all centered on its moons. The European Space Agency will be launching the Jupiter Icy Moon Explorer or JUICE in 2023 which will study Ganymede, Callisto, and Europa. NASA plans to launch the Europa Clipper mission in 2024. Its goal will be to do close flybys of Europa while in orbit around Jupiter.
Depending on what data these missions return, the next step might be a lander on the surface of one of the Galilean moons.
Next to Mars, Jupiter, or to be more precise, Jupiter’s moons, are the largest areas of interest in the solar system.
The presence of ice and the high probability of liquid water beneath the surface of the moons makes it the most likely place in the solar system where some form of basic life may have arisen.
This fact alone will make Jupiter an object of study and inquiry for centuries to come.
Everything Everywhere Daily is an Airwave Media Podcast.
The executive producer is Darcy Adams.
The associate producers are Thor Thomsen and Peter Bennett.
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