Panel #1 (Title)
• This is Outer Space Pals #10. In this episode, we'll learn a bit about the atmospheres of the planets.

Panel #2
• When we say the Sun is gas, that's the easy way to talk about what its made of because three-quarters of it is hydrogen and about one-quarter is helium. Both of those elements are gases on Earth, so we think they act the same on the Sun. And they do, in part. But the Sun also is made of a fourth type of matter (in addition to solid, liquid, and gas) called plasma. Plasma can form only at crazy high temperatures, like those of the Sun and other stars. In plasma, electrons don't orbit the nucleus of a single atom. Instead, they have so much energy that they're free to travel around from atom to atom.

Panel #3
• Mercury and the Moon have no atmosphere. One thing a planet's atmosphere does is to act like a shield against most meteors. In Earth's case, most meteors burn up because of friction with our air. Only the biggest ones land, and only the biggest of those make craters. But Mercury and the Moon have no air, so their surfaces are covered with craters big and small. Take a look at some craters on the Moon taken by the astronauts aboart Apollo 17 (courtesy of NASA):

Panels #4, #5, and #6
• Earth is part of a colorful solar system. And Noah and Rusty are asking some great questions about the reasons.

Panel #7
• How much air a planet can hold depends on only one thing: its mass. Mass is a measure of how much material something contains. The more mass something has, the stronger its gravity will be. Aha! That's why bigger planets have more air, and it's also why they can hold onto lighter gases.

• Oh, and one more thing: mass is not the same thing as weight. Scientists define weight as the gravitational pull on any object. Think of it like this: Take any object on Earth. It has a certain mass. And let's say it weighs 100 pounds. If you moved that object to the Moon, its mass would be the same, but it would weigh only about 17 pounds.

Panel #8
• Earth also has more cloud-making stuff in its atmosphere than Mars does, mainly water in the form of ice crystals. We do see clouds on Mars, but they are much less dense than ours, so they usually don't last long.

Panel #9
• Water ice isn't the only material that can form clouds. The big outer planets have little water in their atmospheres, but they're covered in clouds made of methane, ammonia, and other compounds. When sunlight hits those gases, the gas absorbs certain colors in the sunlight and reflects what's left. For example, methane in Neptune's atmosphere absorbs the red, orange, and yellow colors in sunlight. What's mainly left is blue, so that's the color it looks to our eyes.

Panel #10
• Astronomers have observed large spots on both Neptune and Jupiter. Neptune's dark spots come and go, but we've been watching Jupiter's Great Red Spot for more than 350 years. Oh, and it's huge! The Great Red Spot is about as large as three Earths. All spots like these on planets are storms that move (spin) like hurricanes on Earth. Here's a closeup look at Jupiter's Great Red Spot (courtesy of NASA):

Panel 11
• We'll find out what that really dark spot on Jules is in Outer Space Pals #11.