Oxygen gas is colorless, odorless, and tasteless. 

It's usually purified by fractional distillation of liquefied air, but the element is found in many compounds, such as water, silica, and carbon dioxide.

The red planet is actually many colors. At the surface, we see colors as brown, gold, and tan. The reason Mars looks reddish is due to oxidization—or rusting—of iron in the rocks, regolith (Martian “soil”), and dust of Mars. This dust gets kicked up into the atmosphere and from a distance makes t...