On Earth, hydrogen is found in the greatest quantities as water. It is present as a gas in the atmosphere only in tiny amounts – less than 1 part per million by volume. Any hydrogen that does enter the atmosphere quickly escapes the Earth's gravity into outer space.

What happens to hydrogen in the atmosphere?

In the upper atmosphere, hydrogen may moisten and cool the stratosphere, slowing down the recovery of the ozone layer. In the lower atmosphere, hydrogen may hasten the build-up of the greenhouse gases: methane and ozone and hence contribute to climate change.

Where does hydrogen go in space?

Hydrogen is found almost everywhere in the universe. It occurs between and within stars, and in the enormous gas and dust clouds that exist throughout interstellar space. Scientists have known since the 1970s that bonds between hydrogen atoms form on the very cold surface of interstellar dust grains.