For many years, scientists believed that the atmosphere on Earth was a thick soup that exerted significantly more pressure than today’s atmosphere. As we recently reported, this belief shaped key assumptions about the way life developed throughout the planet’s history. According to a report from Live Science, however, a new study led by scientists at the University of Washington reveals that this assumption couldn’t be further from the truth.

Scientists found their evidence supporting a thin primitive atmosphere in tiny gas bubbles trapped in lava samples. The findings have huge implications for the study of early Earth, as well as for the search for extraterrestrial life throughout the universe.

According to the study’s lead author Sanjoy Som, the director of the Blue Marble Space Institute of Science, “Here you have a young Earth with an atmosphere completely different than today, and yet was very much alive. That makes the early Earth the closest thing we have to an inhabited exoplanet.”

The finding suggests that other planets orbiting different stars may have more hospitable atmospheres for organic life than once thought. Researchers addressed the “faint young sun” paradox, first proposed by Carl Sagan and George Mullen in the 70’s.

Sagan and Mullen suggested that the sun was likely fainter billions of years ago than it is today. The relatively weaker sun, in theory, should have left the Earth a glaciated snowball inhospitable to even the hardiest life forms. The fossil record disagrees with this paradox, however; something was keeping the Earth at a hospitable temperature and providing life with essential building blocks like water and carbon.

The gas bubbles trapped in lava samples from 2.7 billion years ago described in the study may have finally provided a solution to the paradox. By calculating the air pressure of the gases trapped within, researchers showed that the atmosphere was significantly thicker than previous estimates held.

“This would increase the amount of water vapor in the air, which is the strongest of the greenhouse gases,” said Som. The thick atmosphere on early Earth explains the abundance of primordial life – and suggests that other planets throughout the universe may be likely to harbor similar conditions.

A press release from the University of Washington describing the details of the study can be found here.