The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water. There was probably a very much larger amount of carbon dioxide in the Earth's atmosphere when the Earth was first formed, but it has since been almost all incorporated into carbonate rocks and to a lesser extent dissolved into the oceans and consumed by living plants. Plate tectonics and biological processes now maintain a continual flow of carbon dioxide from the atmosphere to these various "sinks" and back again.
The tiny amount of carbon dioxide resident in the atmosphere at any time is extremely important to the maintenance of the Earth's surface temperature via the greenhouse effect. The greenhouse effect raises the average surface temperature about 35 degrees C above what it would otherwise be(from a frigid -21 C to a comfortable +14 C); without it the oceans would freeze and life as we know it would be impossible.
The presence of free oxygen is quite remarkable from a chemical point of view.
Oxygen is a very reactive gas and under "normal" circumstances would quickly combine with other elements. The oxygen in Earth's atmosphere is produced and maintained by biological processes. Without life there would be no free oxygen.

Atmosphere. Whether or not a planet has an atmosphere depends on many things: the mass of the planet, the distance of the planet from the Sun, the amount of volcanism that has occurred on the planet, etc.
Atmospheres can shield a planet from meteor and comet impacts, erode the surface, shield the surface from harmful light like ultraviolet light, trap heat, and moderate temperature, as well as provide gases that plants and animals can breathe.

Mars, for example, like the Earth, will have internal heat sources, and temperatures will be increasing with depth. Water is so common on planetary bodies that it seems almost certain it will be present in large quantity also on Mars, and there must then be a depth range in which it is liquid. If the surface temperature has decreased over geologic times, the depth range of liquid water would have moved a little lower. The surface itself and a thin layer below are cold, so that any water coming up from deeper levels would generally not spill over the surface, but freeze in the rocks. Very little would reach the surface; in contrast to the circumstances on the Earth, where a surface temperature above the freezing point of water allowed all the ocean water to come up and spill over the surface. Small amounts of water vapor have indeed been detected in the Martian atmosphere.

The surface materials will have had a very different chemical history on the Earth as on Mars; but below the surface there will be somewhat similar materials on the two bodies, as represented by a mix of the meteorites, the leftover debris of planetary formation.

Similar out gassing processes seem to have occurred on many other planetary bodies.
Jupiter, Saturn, Uranus, and Neptune have hydrocarbons in their massive atmospheres. Titan, a satellite of Saturn, has a substantial atmosphere in which the hydrocarbons methane and ethane seem to play a role similar to that of water on Earth, forming clouds and probably rain, and as with water here, there must be evaporation from lakes or oceans on Titan to resupply the clouds. In addition to methane and ethane, a number of other hydrocarbon molecules are identified spectroscopically, and they are quite similar to the range of molecules in terrestrial natural petroleum.

There is plenty of oxygen in the universe actually. On this planet oxygen occurs as a diatomic (2) molecule (O2: Chemical structure) and IT originates as a byproduct of photosynthesis. Certain kinds of bacteria, protists (algae) and green plants use sunlight to make tissue and store chemical energy. They also use water to get the hydrogen they need and oxygen is a waste product so they dump it to the atmosphere...lucky for US!!!

On earth, the oxygen of the atmosphere is due to LIFE ON EARTH. However on the other planets of the solar system, if they have life at all, oxygen is not abundant enough to create an oxygen-rich atmosphere like ours...but it is still there!

I think there is plenty of oxygen out there, away from Earth.
Oxygen just tends to react with other chemicals and get locked up
into substances that aren't very useful to oxygen breathers like us.
Plant life here on Earth does a very good job of keeping oxygen in
the atmosphere for us and turning oxygen, carbon, nitrogen, and
hydrogen into substances we can eat.

Actually, scientists have discovered that oxygen exists on other planets in our solar system. Several years ago, that Hubble telescope detected evidence of molecular oxygen in the atmosphere of Europa, one of Jupiter's moons. The temperature on Europa is extremely cold, and there is actually some ice on the surface. Water is composed of hydrogen and oxygen, so there is oxygen any place that there is water, however, the oxygen may not necessarily be in its molecular form. However, on Europa, the ice on the surface is hit by sunlight, dust, and other particles to form water vapor, which, through a series of reactions, breaks down to form molecular hydrogen and oxygen. The atmosphere on Europa is very thin and a balance is formed between oxygen that escapes into space with new oxygen that forms from the ice.