One thing seems to be true in free space, the rule of survival applies writ large, Eat or Be Eaten. The Foundation would like to begin to offer a menu. Contrary to the view that space is empty, our Solar System is filled with millions and millions of small objects. Those that approach the Earth or are easy to reach in terms of energy are called NEOs or Near Earth Objects. These break down into several types, but there are three major categories.
Comets are basically big gravel filled snowballs.
Comprised of quantities of water, methane and nitrogen in ice form mixed with all kinds of rocks and metal, as they approach the sun the solar wind heats some of this material, which then vaporizes and is blown away from the center of the solar system by the solar winds, thus giving us the fantastic tails we see in the sky. Next are carbonaceous chondrites. These appear to be similar to comets, but with most of the volatile gases burned off already. In fact many believe they are in fact the dead cores of comets. Finally come the rocks, which, like rocks here on Earth are solid hunks of mass, leaning either towards a metallic structure comprised of iron nickel and other metals or a mineral based composition.