Hey, Dad, look at me!
M a hen you think of moons, here on Earth long k you probably picture before the dinosaurs. in Wthe familiar silver- g gray moon we see in our own Lunar Leftovers Are they all night sky. But our solar system The planets, moons, asteroids, M made contains more than 165 moons, and comets in our solar system O and they come in all sorts of sizes are actually leftovers from the O russo and types. Some are round, and formation of the sun about 4.6 NS by Charlene B others are irregular, oblong rocks. billion years ago. The solar system Thousands of craters pockmark began as a huge cloud of gas, some moons, while the surfaces ice, and dust. As gravity pulled of others were smoothed by everything to the center of the ancient lava flows or frozen cloud, a slowly turning core of beneath layers of ice. A few closely packed material formed. moons even have atmospheres, As it turned, the cloud began to active volcanoes, or vast oceans flatten out into a disk like pizza
that could support life very similar dough flattening into a pizza as Charlene Brusso © 2009 by to the tiny creatures that lived MoonCards by Amanda Shepherd 6 M ak in g M OO russo the chef NS by Charlene B spins it in the air. The core eventually grew dense rugged rocks in the asteroid belt Jupiter’s giant and massive enough to form the between Mars and Jupiter. red spot eyes sun. The leftover dust and ice Beyond the asteroid belt, the Ganymede, the planet’s farther out in the disk clumped rocky cores of the outer planets largest moon. together into bigger and bigger were massive enough to attract The spot is chunks to make the planets and most of the cloud’s leftover gas. actually a huge storm their moons, the comets, and the They became the “gas giant” plan- high above Maybe we could find ets: Jupiter, Jupiter’s a moon just for surface. Plush.
7 Chips Off the Old Block Earth’s moon got off to a smashing start, which no one suspected until scientists studied moon rocks that astronauts brought back from its surface. Minerals in the lunar rocks show that our moon is the same age as Earth, about 4.5 billion years old. Scientists Saturn, Back then, Earth was still molten— color coded Uranus, and soft and hot. Scientists think an this picture Neptune. The powerful gravity object at least half the size of of Earth’s moon to show of these large planets also cap- Earth—perhaps another planet the different tured more leftover or large asteroid—smashed into minerals it is rocks than did the Maybe I us and knocked off an enormous made of. And can make a no, the orange gravity of the smaller glob of molten rock. The melted is not cheese, planets closest to the sun rock didn’t have enough speed (Mercury, Venus, Earth, to escape Earth’s gravitational and Mars), giving pull. Instead, it cooled and the gas giants many hardened into the moon, more moons than any forever trapped in orbit around of the inner planets. Jupiter has at us. The original object that struck least 63 moons, Saturn at least 59. Earth might still be inside the Uranus has 21 known moons, and moon, hidden under the material it Neptune at least 13. Of the inner blasted off our planet. planets, only Earth, with one, and Scientists think that two of Mars, with two, have moons. Saturn’s moons, Telesto and Calypso, All these moons are made of may have formed from material material from the same cloud of knocked off another moon, Tethys. gas and dust—but that doesn’t Telesto and Calypso are each about mean all the moons in the solar 20 miles across, making them two system are the same. of the smallest moons in the solar system. Their lumpy shapes also
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Goddess of Success Named for: 15 Miles across: Voted: Very Small Named for: Goddess of Fresh Water Named for: Does rocky Telesto mind being among God of Fear Miles across: 662 Miles across: Voted: Very Icy the smallest moons? Heck no! She 16 runs rings around Saturn, even if she Voted: Really Lumpy Fifth largest in Saturn’s huge family of still lives in the same orbit with her You’d be afraid too if you were on moons, Tethys is named for the Greek mother, the goddess Tethys. a crash course with Mars. The goddess of fresh water, even though the planet’s gravity is pulling little Phobos moon is made mostly of ice and rock. down so that the two will collide in 50 million years.
suggest that they are pieces bro- have elliptical, or ken off a larger object rather than oval-shaped, moons formed from molten rock in orbits and the early solar system. tend to circle the planet at Gotcha! an angle above Some moons may be chunks or below the of rock and ice that got close planet’s middle. enough to be captured by a Scientists planet’s gravity. How can we tell? think Mars’s rocky, Moons, like ours, that formed at oddly shaped the same time as a planet tend moons, Phobos and Ferryman of the to be round. They usually move Deimos, are cap- Named for:
in circular orbits around the tured asteroids. The Underworld 750 Miles across: planet’s middle, traveling in the outermost moons Voted: Coldest same direction that The largest of Pluto’s three Step aside. moons is almost half the dwarf the planet spins. Moon coming planet’s size and orbits a cozy through. Captured moons, 12,000 miles away. on the other hand,
ask 9 the original dust cloud that formed the solar system litter the Kuiper Belt. Kuiper Belt objects (KBOs) are some of the oldest things in the solar system. They come in all sizes and shapes, and they are made mostly of rock, minerals, and ice. KBOs interest scientists because these ancient rocks reveal what the solar
How did they system was like billions of years get ago. Neptune’s moon Triton and orbiting the dwarf planet Pluto and its Jupiter, Saturn, moon Charon are the largest KBOs Triton is the Uranus, and Neptune are prob- in the solar system. largest of Neptune's 13 ably also captured moons, but moons. they came from the Kuiper Belt, On the Surface the region at the edge of the solar system. Icy rocks left over from
Named for: A Greek River Fairy Miles across: A Member of the Titans, a 2,230 Named for: Voted: Most Volcanic Family of Ancient 246 Greek Gods Miles across: This moon’s got it all! Lava! Gas! Huge Voted: Most Cratered tides! Bubbling and boiling Io has the most volcanoes in the solar system. What’s it like to be the closest moon to Its surface bulges in and out as Saturn? Hard work. Mimas’s gravitational Jupiter’s gravity tugs on it. pull keeps some of Saturn’s famous rings 10 a s k in line. A moon’s surface tells a lot about rock cooled into the smooth plains its past. Craters and large flat we call maria. areas of dark rock called maria Mimas, one of Saturn’s moons, (Latin for “oceans”) cover our is covered with many tiny cra- moon. The craters on the moon ters and one gigantic one named are very old. They tell us that after astronomer William Herschel. when the planets and moons Enormous cracks spread across the were forming and cooling, lots of surface on the side of the moon loose debris was zipping around opposite Herschel (the crater, not the solar system. Most moons are the astronomer). Scientists think covered with craters where these that some large object smacked young space rocks crashed into into Mimas early in its history. The them. impact created the giant crater and The dark, flat areas on our caused the large cracks—stress My moon shines by reflected moon show that long ago it fractures—on the opposite side. If bubbled with volcanoes. Molten the object that hit Mimas had been rock erupted from the inside and any larger, it might have shattered spread across the surface, filling in the moon into rubble. some of the craters. The volcanic Living Moons
Named for: A Family of Ancient Greek Gods Named for: 3,200 A Phoenician Princess Miles across: Another Greek Titan Miles across: Named for: Voted: Most Mysterious 505 Voted: Most Likely 1,940 to Support Life Miles across: Covered in clouds and haze, Titan has- Voted: Best Spitter Under that icy exterior lurks a giant an atmosphere something like a plan ocean containing twice the amount of Enceladus has become famous et. Hundreds of lakes filled with liquid water on Earth. Constant movement for spraying icy material high chemicals called hydrocarbons dot its of the ocean causes the cracks in the above its surface at speeds up surface. moon’s surface. to 1,000 miles per hour. ask 11