Oxygen Oxygen is a Group 16 element. Oxygen is the third most abundant element found in the sun, and it plays a part in the carbon-nitrogen cycle, one process responsible for stellar energy production. Oxygen in excited states is responsible for the bright red and yellow-green colours of the aurora. The atmosphere of Mars contains about 0.15% oxygen. About two thirds of the human body, and nine tenths of water, is oxygen. The gas is colourless, odourless, and tasteless. Liquid and solid oxygen are pale blue and strongly paramagnetic. Ozone (O3) is formed from electrical discharges or ultraviole