Have you ever wondered what causes red rocks? Red rocks like those on the surface of Mars, the red planet, or the canyons of Utah. The answer to this question comes down to two common elements, iron and oxygen, which combine together to form the compound rust. Most people have heard of or seen rust. It’s that red crusty stuff that forms on the outside of nails or other bits of metal that have been outside too long. But what is rust? The most common type of rust is formally named Iron (iii) Oxide. This iron oxide compound has two iron atoms and three oxygen atoms all bunched together. This compound is formed in just the right way so that most colors of light are absorbed by it, but red light is reflected. The reflected red light makes rust appear red and thus make red rocks look red.So we now know that red rocks get their distinctive color because of rust, but how did that rust get there? Why was it formed in the first place? To answer this question we must look deeper into the chemistry of iron and rust. Rust is caused when iron is exposed to amounts of oxygen, such as the oxygen in air or in water. A chemical reaction takes place between the iron and the oxygen. The oxygen oxidizes the iron and steals several of its electrons. The iron now has a positive charge and the oxygen has a negative charge and because opposite charges attract, they are drawn together to form iron oxide or rust. Red rocks, then, are rocks that have a fairly high concentration of iron in them and are exposed to some source of oxygen. The combination of these two things creates rust and turns the rock red.The reaction that forms rust is actually very interesting. It’s what is called an endothermic reaction, or in simpler terms the reaction gives off heat. In nature things rust very slowly, so that heat is also given off slowly and you can really tell. However, there are ways to speed up reactions, which is what scientists and engineers did when they created air activated hand warmers. Iron is put in these hand warmers and begins a very sped up reaction with oxygen when the package is opened and thus creates heat. It’s pretty cool that the same process that named Mars the red planet can also keep your hands warm on a cold day.