Free
There are several theories as to how the Moon formed.
Most scientists believe that about 4.5 billion years ago, a small planetary body smacked into Earth. At the time, our planet was still young—just 100 million years old! The collision threw pieces of debris into orbit, which then joined together and became the Moon. Both Earth and the Moon spent the next 700 million years under siege from giant meteorites. Earth’s scars from that time have mostly healed, thanks to weather, erosion, and plant life. But the Moon still bears huge pockmarks, which we call craters.
The last stage in the Moon’s formation happened over the next 2 billion years. Molten lava seeped up from below the surface, forming dark areas called maria (MA-ree-uh), or seas. As this activity decreased, the Moon’s surface hardened into the grayish-green crust we see today.
◀ Scientists are not exactly sure what lies beneath the Moon’s hard outer crust. They believe the Moon has a mantle, made of dark rock. Below that is a partly molten region, and finally a small core probably made of iron.
◀ The Moon is shrinking because it’s gradually cooling from the inside out. As the interior cools, it shrinks, and as it shrinks, it pulls everything in toward the center. The motion creates faults on the surface, which produce quakes (in this case, moonquakes). This is the conclusion scientists published in May 2019 after reviewing eight years of data recorded by devices left on the Moon during the Apollo missions (1969 to 1972). By scientists’ estimates, the Moon is about 150 feet leaner than it was several hundred million years ago. The shrinking and the quakes continue.
A typical weather report from the Moon would be brief. There is no weather on the Moon—no clouds and little or no atmosphere (the gases that surround a planet). The sky is always black and starry, and there is only a whisper of wind, caused by the Sun. That is why craters created billions of years ago remain practically unchanged. ▶
-Weather_520.jpg)
_1060.jpg)
◀ No life exists in the Moon’s dusty soil, which is called regolith, but it has minerals, including aluminum, iron, and titanium. Astronauts brought back three main types of rocks. Basalts (blue, pictured) are dark, hardened lava. Anorthosites (red, pictured) are light rocks in the highlands. Breccia are composites, made when other rocks were crushed together during meteorite impacts.
The gravity on the Moon is one-sixth of the gravity on Earth. So a person who weighs 180 pounds on Earth would weigh only 30 pounds on the Moon! ▶
-Gravity_520_1.jpg)
