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Module 1 - The Solar System

The Asteroid Belt

Asteroids are material left over from the formation of the solar system. One theory suggests that they are the remains of a planet that was destroyed in a massive collision long ago. More likely, asteroids are material that never coalesced into a planet. In fact, if the estimated total mass of all asteroids was gathered into a single object, the object would be less than 1,500 kilometers (932 miles) across, less than half the diameter of our Moon. The asteroid belt lies in the region between Mars and Jupiter. The Trojan asteroids lie in Jupiter's orbit, in two distinct regions in front of and behind the planet. *Image Credit*: Lunar and Planetary Institute

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Solar System Debris Small Bodies or Solar System Debris

In addition to the major planets the solar system contains a large number of small bodies, which are officially referred to as, well, Small Bodies. Small bodies are primarily Asteroids and Comets. As we will see, they play an important role, primarily early in the history of the solar system. Since we are focussed on planetary processes in this course, we will only describe them briefly here. (Note: Dinosaurs would vigorously disagree with this seeming neglect. 65 million years ago an impact of a several mile wide asteroid created the Chicxulub crater now hidden on the Yucatan Peninsula and beneath the Gulf of Mexico)

Asteroids like those at the top of the page are rocky bodies, most of which revolve around the sun in a position between the orbits of Mars and Jupiter (Asteroid Belt). Like the planets they revolve around the sun, but in shape and size they are more like satellites. The largest asteroid, 1 Ceres is 974 km in diameter. Overall the total mass of all asteroids is less than that of our moon. For more information, click here.

Small chunks of these rocky bodies entering our atmosphere provide us with meteorites, which are very important to our understanding of the formation of the solar system.
Any planetary surface in the solar system is a place one might find meteorites. Here is one on Mars:

Comets are a totally different class of objects, moving on elliptical orbits. Ice objects with minor amounts of rock fragments, they range in diameter from 1 to more than 10 km. Comets are thought to originate in the far outer reaches of the solar system, referred to as the Oort Cloud and the Kuiper Belt. On their path through the inner solar system, inside Mars orbit, their icy nuclei partially vaporize, forming large tails of gas and dust.
Arguably the most famous comet is Comet Halley, which returns to the inner solar system every ~76 years and can be traced back 239 BC. In 1986, an armada of five spacecraft from the USSR, Japan, and the European Community visited Comet Halley. ESA's craft Giotto approached within 540 km +/- 40 km of Halley's nucleus and obtained the best close-up photo.
This is that image:
As an illustration of how far space science has progressed, please contrast that image with the images from ESA's recent Rosetta mission to the lesser known comet 67P/Churyumov-Gerasimenko (alternatively check here). As part of that mission, the probe Philae also landed on the comet, though not totally successfully. Below is a picture of comet 67P/Churyumov-Gerasimenko from 177 miles away. The comet is 4.3 by 4.1 km.
Similar to Halley`s comet, this comet was also heating up and ejecting gases in violent outbursts. And here is an image of one of the outbursts:

ESA has now (June 2018) made the complete Rosetta Image Archive available to the public. You'll find link to images from Earth swing-bys to remarkable close-ups of the comet's surface. If you don't feel that you can spend hours browsing through thousands of images, take less than 3 min to watch the movie below. It's a compilation of the last few hours of Rosetta's decent to the comet. Information and links to download it in several formats can be found here.

Beyond the debris, mostly nothingness
The final component of the solar system is the Interplanetary medium. For the purposes of our course, it is essentially a vacuum and we will not mention it further.