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Even though the Sun is 150 million kilometers away,
the heat that reaches Earth drives all the weather and climate on our planet.
But way out in the solar system, the amount of heat from the Sun drops off dramatically,
so the gas giants get just a tiny percent of the solar radiation that reaches Earth.
And yet, some of these planets’ most noticeable features
are bright spots and dramatic stripes, which are telltale signs of intense weather.
And it’s not an illusion: There is raging weather on these planets,
and it’s not driven by the weak energy they get from the Sun.
Instead, their weather is fueled from the inside out.
This so-called internal heating is not a rare phenomenon at all,
so the better we get to know these internal heat sources,
the better we can understand how they drive weather within our solar system
and on much more distant worlds.
Unfortunately, there’s no simple, one-size-fits-all explanation for internal heating.
It has different origins on different planets, and the effects vary too.
In our solar system, Jupiter creates more internal heat than any other planet.
It’s radiating out 70% more heat than it gets from the Sun.
Scientists think that’s because it’s still contracting:
It’s so massive that the outer layers are constantly squeezing the material at the core,
putting it under huge amounts of pressure.
Inside, things work kind of like a pressure cooker.
As the pressure rises, particles move faster, which means the temperature goes up.
Then, massive convection currents transport this heat from the core
through thousands of kilometers of liquid hydrogen to a layer just beneath the clouds.
There, it acts like a warm tropical ocean fueling a hurricane.
It powers the spiraling storms you can see all over the surface of Jupiter,
and because the internal heat never changes, hurricane season on Jupiter lasts all year long.
It also produces another interesting feature:
Since this internal heat radiates out evenly, Jupiter’s temperature
doesn’t vary between the poles and the equator;
even its poles are as warm as the rest of the planet!
As unusual as it sounds, Jupiter’s not an oddball.
Something similar seems to be happening on Neptune,
which gives off more than twice as much heat as it gets from the Sun.
That makes it about the same temperature as Uranus,
even though it’s roughly one-and-a-half billion kilometers farther from the Sun.
Scientists believe that, like Jupiter, Neptune is also still contracting,
creating that pressure cooker in its core.
And that seems to fuel an atmosphere full of turbulent storms and supersonic winds
that can reach more than 2,400 kilometers per hour.
That internal heat also seems to be what sets it apart from Uranus.
The two planets are known as “twins,” because their size and composition is so similar,
but Uranus has no internal heat source, so its surface is mostly smooth and calm.
Uranus is actually the only gas giant in our solar system that doesn’t produce its own heat, though.
Saturn, the one remaining gas giant, also radiates more heat than it receives from the Sun.
But Saturn isn’t contracting like Jupiter and Neptune.
Instead, scientists believe most of its heat comes from
helium condensing in clouds and raining down toward the core.
As helium droplets fall, friction with the atmosphere creates a tiny amount of heat.
Since helium rain is constantly falling across Saturn,
those tiny bits of heat combine to warm up the entire planet.
All that heat has a pretty significant effect on Saturn’s climate.
It doesn’t just drive the types of storms we see on Jupiter and Neptune, either;
it also shapes Saturn’s seasons.
The giant planet is on an axis that’s a lot like Earth’s,
so we’d expect it to experience seasons a lot like ours.
And there are some seasonal changes in Saturn’s atmosphere,
but they’re way less pronounced than what you’d expect.
That’s because the main source of heat is internal, so the tilt of its axis doesn’t matter much;
temperatures stay pretty even all year long.
If we didn’t know about internal heating, the weather on these giant planets would be pretty baffling.
So figuring out the causes and effects of internal heating
is important for understanding the weather of many planets.
Gas giants are the ones that are most likely to produce lots of heat internally,
because their fluid layers can contract and move around more easily,
but rocky planets like Earth are no strangers to internal heating either.
Our planet still has a lot of heat left over from its formation,
but scientists estimate that nearly half of Earth’s internal heat
is being constantly generated by the radioactive decay of elements in the core.
The heat that releases helps churn up metals in the core, which powers our magnetic field,
and drives the movement of magma, which gives us plate tectonics.
So, internal heat is at work in a lot of places, including our own planet.
And the better we understand how internal and external heating work together in our own solar system,
the better we can predict what conditions will be like on other, far-off worlds.
Thanks for watching this episode of SciShow Space!
And to learn even more about the wild weather on other worlds,
you can check out our episode on exoplanets with extreme weather right after this.
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