Part A
Asteroids
Asteroids are non-cometary, Small Solar System Bodies 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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Go to the Wikipedia's Asteroid web page. Focus on the following sections: "Classification", "Characteristics - Size Distribution", and "Distribution Within the Solar System". Answering Quiz Me! questions A01 through A06 after reviewing these relevant sections.
Now, let's look at a few spacecraft missions that have recently targeted asteroids. Go to NASA's Asteroid web page, scroll down the page to the "Featured Asteroids" section and review the information relating to Apophis, Bennu, Psyche, Itokawa, Eros, Didymos, and Vesta. Then answer Quiz Me! questions A07 through A09.