Currently slated for a launch in the spring of 2019, NASA’s James Webb Space Telescope (JWST) will be humankind’s most powerful eye in the sky till date once it is up in orbit. Among other things scientists hope it will find and study, it will also look for water in interstellar space.

Interstellar space refers to the large distances between the spheres of influence of stars. Far from being a vacuum, these spaces are full of dust, gas and a myriad of chemical molecules — ranging from the simplest element hydrogen to complex carbon-containing organic compounds. These chemicals don’t drift in space by themselves, but need the protection of a molecular cloud to survive the ultraviolet radiation in space.

Molecular clouds of massive interstellar clouds within which the dust protects the water and other compounds from damaging radiation, and the conditions inside also promote chemical reactions. These clouds contain the bulk of all the water present in the universe, and the Webb Telescope will study one such cosmic reservoir.

Hydrogen and oxygen atoms come together on the surfaces of tiny dust particles inside molecular clouds to form water, while hydrogen and carbon combine to form hydrocarbons, both necessary ingredients for life as we know it. Ammonia, another important constituent, is formed when hydrogen and nitrogen come together. Over millennia, as more molecules stick to the dust surfaces, they accumulate layers of ice.

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