Part A
Asteroids
Asteroids are non-cometary objects of varying size that orbit the Sun in different locations, but mostly no further than the orbit of Jupiter. There are millions of these objects, likely the fragments of larger planetesimals that never grew large enough to become planets in the early forming Solar System. Asteroids vary greatly in size, from almost 1000 km for the largest down to rocks just 1 meter across. The largest ones, sometimes referred to as "minor planets", "planetoids", or "planetesimals" include Ceres, Pallas, Juno, Vesta, etc. Most asteroids are much smaller, irregular bodies that orbit between Mars and Jupiter, and are typically heavily cratered. They can resemble a pile of loose rubble (like Itokawa) and some even have small moons (like Ida). Although we are just beginning to examine these objects directly and in detail with various spacecraft (like NEAR Shoemaker, Dawn, and others), we can learn much from many kinds of meteorites that are actually asteroid fragments. Let's do a quick review.
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Figure 5-2. Stereotypical potato-shaped asteroids. At left, asteroid 243 Ida and its tiny moon Dactyl as seen by the Galileo spacecraft about 14 minutes before its closest approach on August 28, 1993. At right, the Near Earth Asteroid 433 Eros as seen from the NEAR Shoemaker spacecraft in 2001. |
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We will mainly use information from the Wikipedia web site. A few descriptive articles from Astronomy magazine will supplement the online information. Let's start by reviewing some of the basic information about meteorites.
Go to the Wikipedia's Asteroid web page to answer Quiz Me! questions A01 through A09. Read the relevant section and before answering each question.
