Rocks and Dust in the Planetary Neighborhood

Abstract

The planet we live on, the Earth, is a chunk of rock partially covered with liquid water and overlaid with a thin blanket of gaseous atmosphere. Liquid oceans and polar ice caps cover three quarters of the Earth’s surface. The continents, on which we walk and build our cities and villages, are made up of rocks. However, the rocky crust of the Earth is not limited to the continents, but extends to the ocean floors. These rocks are aggregates of minerals, which are solid-state compounds of common elements such as oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium. Three of our Solar System neighbors: Mercury, Venus, and Mars, have similar rocky surfaces and the four together are collectively known as the “terrestrial planets”. The rocky nature of Mars is most vividly illustrated by the landscape images sent back by the Martian rovers Spirit, Opportunity, and Curiosity. In contrast, the other four planets in the outer Solar System—Jupiter, Saturn, Uranus, and Neptune —are gaseous in nature and do not possess a solid surface. The only anomaly is Pluto, the outermost member, is believed to be made up of water ice.