We've talked about what kinds of uncomfortable and ultimately fatal things would happen to you if you stepped out onto the surface of Mercury, Venus, or Mars.

But what about the planets that don't have much of a surface to speak of?

As we continue our journey throughout the solar system, we've reached Jupiter and Saturn, the largest of the gas giants.

If your spacecraft were to venture into their atmospheres, would you ever hit anything solid? And what's the climate like in there?

'Not hospitable' would be putting it nicely.

Jupiter and Saturn are mostly just helium and hydrogen with a much higher percentage of the latter.

Scientists think this may be because the gas giants formed early in the solar system's history, which allowed them to accumulate enormous amounts of the two lightest gasses.

Jupiter is 90 percent hydrogen but its also twice as massive as the rest of the planets in the solar system combined. It's so big, that were it to be about eighty times larger, Jupiter would be considered a small star.

Saturn has even more hydrogen - 96 percent - along with 3 percent helium. And, like Jupiter, it contains small amounts of methane, ammonia, and water.

Because it's so light and gassy, Saturn is 95 times as large as Earth but only 12 percent as dense. So if you could somehow set up an experiment within an enormous celestial laboratory, you'd find that Saturn would float on water.

Now, just getting close to either planet would be challenging for our theoretical spacecraft. Jupiter has the strongest magnetic field in the solar system, and its radiation belts are strong enough to cripple any spacecraft and kill any human that got within 300,000 kilometers of it.

Radiation emitting from Saturn is relatively weak by comparison.

But the question remains, does a surface exist on either planet?

The answer is yes, but where exactly it is depends on what you mean by surface. Scientists define the surface of a gas giant as the point where the atmospheric pressure is equal to the atmospheric pressure on the surface of Earth, or one bar.

So on the 'Surface' of Saturn, you'd experience clouds of ammonia ice, winds of up to 1600 kilometers an hour, and bolts of lightning a million times more powerful than those on Earth.

At this level on Jupiter, the weather's no better, which we know because we've actually crashed a probe into Jupiter's heart to see what was in there.

On September 21st 2003, 14 years after leaving Earth and 8 years after it began to explore the Jovian system, far enough away that it wouldn't get fried from radiation, the Galileo orbiter ended it's mission by sending itself into Jupiter's atmosphere.

Galileo wasn't equipped with cameras, but the spacecraft had instruments to measure weather conditions and cloud composition. Those instruments sent back data until the probe made it to 150 kilometers below Jupiter's equivalent of sea level. At which point, it disintegrated.

Galileo reported winds of 700 kilometers an hour as it descended through layers of ammonium hydro-sulfide. And scientists were surprised by the high temperatures and density in Jupiter's clouds. The last data Galileo sent to Earth reported air pressure of 22 bars, and a temperature of 151 Celsius.

But what if we were able to build an unbreakable probe? Something totally indestructible that would go as far as possible into Jupiter and Saturn? Would it be able to pass right through them?

The answer is almost definitely no, and this is where things get really strange. In addition to their more scientifically defined surfaces, both Saturn and Jupiter are thought to have solid or semi-solid cores, about twenty times the mass of Earth.

No one is really sure what they're made of, most guesses are that if it's solid, it's probably iron and other rocky material. But, what surrounds the inner core of both planets is believed to be a weird, dense mixture of liquid metallic hydrogen.

Chemically speaking, atoms are metallic if they easily lose their outer electron. At the center of these gas giants, the temperature and pressure are so high, that scientists think that electrons could be released from hydrogen molecules, essentially turning it into a liquid metal.

And this is why Jupiter has such an enormous and dangerous magnetosphere. Jupiter completes one rotation every 9.9 hours, giving it the shortest day in the solar system.

And the incredibly fast spinning metal core generates electrical currents, creating a powerful magnetic field more than 7,000,000 kilometers long.

So, Jupiter and Saturn - who'd have thought that gas could be so fascinating?

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