Asteroids: little worlds Space between orbits of Mars and Jupiter seems empty of planets

In 1800, the first of the minor planets, Ceres, was discovered. After that many others were discovered and named after Roman deities (Vesta, Pallas, Calliope, etc). Look at Figure 2-2 one more time! Now we know the space between the orbits of Mars and Jupiter looks like:

Presently known asteroids

Until the 1990s, there were no images of asteroids. Missions by robot spacecraft have changed that Gaspra

There are now 5 asteroids that have been visited by spacecraft, with two landers

Most recent result, visit of spacecraft Hayabusa to asteroid Itokawa

One of the more intriguing properties of asteroids: Kirkwood’s Gaps. Make a histogram of semimajors axes of orbits, and what do you get?

Kirkwood’s Gaps are there because of orbital resonances with Jupiter, just like the structure in the rings of Saturn. “Jupiter is throwing rocks at us”

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