<human>:  Are all the elements plants need for photosynthesis present in atmosphere of Mars?
<bot>: Yes, all the elements plants need for photosynthesis are present in the atmosphere of Mars. Plants need three elements for photosynthesis: Hydrogen, Oxygen, and Carbon and the atmosphere of Mars is composed of carbon dioxide, nitrogen, argon, and trace levels of water vapor, oxygen, carbon monoxide, hydrogen and other noble gases, so all the elements plants need for photosynthesis are present in the atmosphere.