PLANETARY SCIENCE

Learning about Planets

Want to know how a planet formed? What shaped its surface? Where its moons came from? What will happen to it? Then you want to study planetary science. This field covers all objects in the solar system and how they came to be the way they are. What scientists learn in that field can be applied when they observe planets orbiting other stars, too. Planetary science began as a subdiscipline of astronomy but quickly branched out. Today, a good planetary scientist must know:

• Geology
• Geochemistry
• Geophysics
• Atmospheric science
• Glaciology
• Oceanography

If you’re planning to go into this field, you’ll even study a little spacecraft engineering in order to design and build instruments for planetary exploration.

Processes That Shape Planets

The basics of planetary science are similar to the principles of geology. Assuming that you’re studying a world with a hard surface—a rocky planet or moon, an asteroid, or a place with an icy surface such as a comet or a frozen moon—there are several processes that can affect that place. The first is tectonism. This affects the outer layer of a planet or a moon, and it happens very slowly. It’s caused by heat escaping from under the crust of the planet. As it does, it warps the surface, causing it to fold or create faults (fractures).

The second process that affects a hard-surfaced world is impact cratering. Debris has smashed into the surfaces of most solar system objects, ranging from Mercury to Mars, out to the moons of the gas giant planets. It’s likely the dwarf planet Pluto and its cohorts in the Kuiper Belt also have impact craters.

Much of the cratering occurred early in the solar system’s history, during a period called the Late Heavy Bombardment. However, impacts continue to occur as errant solar system stuff crashes into planets, moons, and asteroids. The study of impacts gives us a handle on the collisional history of the solar system, particularly in the early epochs when smaller bits of solar system material merged to form larger worlds.

A third process that affects planets is weathering. It occurs when surfaces are affected by interactions with water, wind, and vegetation. We see plenty of all three on Earth. Flowing water and wind erode rock, and plants such as mosses can break down rocks as well. Chemical weathering is also at work across our planet. It occurs when acid rain dissolves rocks, for example. Windstorms scour the landscapes, and the freezing-thawing cycles that accompany winter and summer weather can crumble rocks, too. There are also signs of weathering on the surfaces of Mars and Venus, caused by contact with the atmosphere, and on Mars by the action of liquids that flowed across its surface in the very distant past.

Volcanism is another major force that changes the surfaces of solar system worlds. We are most familiar with the volcanoes on Earth, which belch lava and clouds of poisonous gases. There are volcanoes on the continents as well as in the deep ocean. Essentially they convey heat from beneath the crust of our planet and in the process resurface the land and seascapes.

Planetary Atmospheres

The study of atmospheric blankets around planets (and some moons) focuses on the processes that create and sustain atmospheres, as well as their structures and effects on the planet. Atmospheric scientists also study interactions between a planet’s blanket of air and its magnetic field. These days climate change is in the news, and this makes the study of Earth’s long-term atmospheric changes and their effects on our climate all the more important. Various space agencies have launched satellites to monitor our warming atmosphere from space. Ground-based research also includes studying interactions between the global oceans and the atmosphere.