It is thought to pose no risk to our planet, according to NASA data.
A team of scientists focused on an area containing two of Venus' largest volcanoes, Ozza and Maat Mons.
Astronomers describe it as the missing link in the origins of life as we know it.
Experts said the detailed chart sheds fresh light on global warming.
The five-year study found the gases fuel trillions of microbes in the sea.
Few spend enough time in the 'habitable zone'
It confirms Earth was formed partly from carbonaceous meteorites from asteroids in the outer main-belt.
The team discovered three new near-Earth asteroids (NEAs) hiding in the inner Solar System.
It follows on from a previous report five years ago which was signed by more than 15,000 scientists in 184 countries.
It happened more than three-and-a-half billion years ago - before life on Earth began.