Studying Europa's chemistry - on the surface and within the suspected ocean - is important for understanding its habitability because living things extract energy from their environments via chemical reactions. Interactions between materials from Europa's surface and those in an ocean environment beneath the ice could produce elements essential for life such as carbon, hydrogen, nitrogen, oxygen, phosphorous and sulfur.
Europa's surface is mostly water ice (H2O), but the surface is bombarded by intense radiation from Jupiter, which can alter the chemistry of the ice. Through this process, the hydrogen and oxygen from water ice can combine with other materials on the surface to create a host of molecules like free oxygen (O2), hydrogen peroxide (H2O2), carbon dioxide (CO2) and sulfur dioxide (SO2).
If these compounds are finding their way into an ocean as part of an ongoing cycle, they could be used to power the reactions living things depend upon. Meanwhile, cycling of ocean water through minerals in the seafloor could replenish the water with other chemicals that are crucial for life.
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