Space

Jupiter doesn’t have a surface. How is that possible?

Jupiter doesn't have a surface: Gray ball with many very swirly bands on a black background.
NASA’s Juno spacecraft captured this image of Jupiter in 2020. How is it possible that Jupiter doesn’t have a surface? Image via NASA/ JPL-Caltech/ SwRI/ MSSS/ David Marriott.

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  • Jupiter is a giant gas planet and the largest planet in our solar system.
  • But Jupiter has no surface. It’s made of gases that get increasingly dense as you head toward the center. Its interior is extremely inhospitable.
  • If Jupiter didn’t exist, life on Earth probably wouldn’t exist either. That’s because Jupiter protects us from incoming asteroids and comets.

By Benjamin Roulston, Clarkson University

Jupiter doesn’t have a surface. But how?

The planet Jupiter has no solid ground or surface, like the grass or dirt you tread here on Earth. There’s nothing to walk on, and no place to land a spaceship. But how can that be? If Jupiter doesn’t have a surface, what does it have? How can it hold together?

Even as a professor of physics who studies all kinds of unusual phenomena, I realize the concept of a world without a surface is difficult to fathom. Yet much about Jupiter remains a mystery, even as NASA’s robotic probe Juno begins its 9th year orbiting this strange planet.

Jupiter’s mass is 2 1/2 times that of all the other planets in the solar system combined.

First, some facts

Jupiter, the 5th planet from the sun, is between Mars and Saturn. It’s the largest planet in the solar system, big enough for more than 1,000 Earths to fit inside, with room to spare.

While the four inner planets of the solar system – Mercury, Venus, Earth and Mars – are all made of solid, rocky material, Jupiter is a gas giant with a composition similar to the sun. It’s a roiling, stormy, wildly turbulent ball of gas. Some places on Jupiter have winds of more than 400 mph (640 km per hour), about three times faster than a Category 5 hurricane on Earth.

A photograph of the planet Jupiter swathed in swirly blue, brown and gold bands.
NASA’s Juno spacecraft took this image of the southern hemisphere of Jupiter in 2017. Image via NASA/ JPL-Caltech/ SwRI/ MSSS/ Gerald Eichstadt/ Sean Doran.

Searching for solid ground

Start from the top of Earth’s atmosphere, go down about 60 miles (roughly 100 km), and the air pressure continuously increases. Ultimately you hit Earth’s surface, either land or water.

Compare that with Jupiter: Start near the top of its mostly hydrogen and helium atmosphere, and like on Earth, the pressure increases the deeper you go. But on Jupiter, the pressure is immense.

As the layers of gas above you push down more and more, it’s like being at the bottom of the ocean. But instead of water, you’re surrounded by gas. The pressure becomes so intense that the human body would implode: You would be squashed.

Go down 1,000 miles (1,600 km), and the hot, dense gas begins to behave strangely. Eventually, the gas turns into a form of liquid hydrogen, creating what can be thought of as the largest ocean in the solar system, albeit an ocean without water.

Go down another 20,000 miles (about 32,000 km), and the hydrogen becomes more like flowing liquid metal, a material so exotic that only recently, and with great difficulty, have scientists reproduced it in the laboratory. The atoms in this liquid metallic hydrogen are squeezed so tightly that its electrons are free to roam.

Keep in mind that these layer transitions are gradual, not abrupt. The transition from normal hydrogen gas to liquid hydrogen and then to metallic hydrogen happens slowly and smoothly. At no point is there a sharp boundary, solid material or surface.

Cutaway diagram of interior layers of Jupiter, including its core.
An illustration of Jupiter’s interior layers. One bar is approximately equal to the air pressure at sea level on Earth. Image via NASA/ JPL-Caltech.

Scary to the core

Ultimately, you’d reach the core of Jupiter. This is the central region of Jupiter’s interior, and not to be confused with a surface.

Scientists are still debating the exact nature of the core’s material. The most favored model: It’s not solid, like rock, but more like a hot, dense and possibly metallic mixture of liquid and solid.

The pressure at Jupiter’s core is so immense it would be like 100 million Earth atmospheres pressing down on you. Or two Empire State buildings on top of each square inch of your body.

But pressure wouldn’t be your only problem. A spacecraft trying to reach Jupiter’s core would be melted by the extreme heat: 35,000 degrees Fahrenheit (20,000 C). That’s three times hotter than the surface of the sun.

An image of Jupiter featuring brown, beige and orange belts along with a large, oval orange spot.
Voyager 1 took this image taken of Jupiter. Note the Great Red Spot, a storm large enough to hold 3 Earths. Image via NASA/ JPL.

Jupiter helps Earth

Jupiter is a weird and forbidding place. But if Jupiter weren’t around, it’s possible human beings might not exist.

That’s because Jupiter acts as a shield for the inner planets of the solar system, including Earth. With its massive gravitational pull, Jupiter has altered the orbit of asteroids and comets for billions of years.

Without Jupiter’s intervention, some of that space debris could have crashed into Earth. If one had been a cataclysmic collision, it could have caused an extinction-level event. Just look at what happened to the dinosaurs.

Maybe Jupiter gave an assist to our existence, but the planet itself is extraordinarily inhospitable to life. At least, life as we know it.

The same is not the case with a Jupiter moon, Europa, perhaps our best chance to find life elsewhere in the solar system.

NASA’s Europa Clipper, a robotic probe that launched in October 2024, will do about 50 flybys over that moon to study its enormous underground ocean.

Could something be living in Europa’s water? Scientists won’t know for a while. Because of Jupiter’s distance from Earth, the probe won’t arrive until April 2030.

Benjamin Roulston, Clarkson University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: Jupiter doesn’t have a surface. It’s a gas giant planet with a hostile interior. But if Jupiter didn’t exist, life would probably not exist on Earth.

The Conversation

Posted 
November 8, 2024
 in 
Space

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