Page 29 - Life beyond the Karman

Asteroids
Asteroids are giant rocks. They exist in their millions and most orbit the sun in a belt between the orbit of Jupiter and Mars known as the Asteroid Belt. Some have orbits that take them across the paths of the inner planets such as Earth and Mercury.
A few asteroids have an orbit that takes them perilously close to Earth or other planets.
Asteroids are hard to see and consequently, they weren’t discovered until the 19th century, when telescopes became sophisticated enough to make them out. Through a telescope, an asteroid looks like a faint star, just a dot of light.
The largest known asteroid, Ceres, is about a quarter the size of the moon and is considered a dwarf planet.
Aurora
Aurora is a luminous phenomena of Earth’s upper atmosphere that primarily occurs in high latitudes in both hemispheres; in the Northern Hemisphere they are called aurora borealis, aurora polaris, or northern lights, and in the Southern Hemisphere they are called aurora australis or southern lights.
Auroras are caused by the interaction of energetic particles (electrons and protons) of the solar wind with atoms of the upper atmosphere. Such interaction is confined for the most part to high latitudes in oval-shaped zones that surround Earth’s magnetic poles and maintain a more or less fixed orientation with respect to the sun. Auroral emissions typically occur at altitudes of about 100 km (60 miles); however, they may occur anywhere between 80 and 250 km (about 50 to 155 miles) above Earth’s surface.
Comets
Comets are giant lumps of ice and dust that have highly elliptical orbits. They can spend centuries in the outer reaches of the solar system before swooping close to the sun and developing tails as they warm up.
Comets are made of ice and dust while asteroids are made of rock. Both asteroids and comets are debris left over from the spinning mass of matter from which the solar system arose almost five billion years ago.
LIFE BEYOND THE KÁRMÁN LINE - OUTER SPACE
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