Although it’s possible Mars once supported life, Earth is the only planet in the solar system currently known to do so. However, a new study notes that Venus may have been habitable for a few billion years — until something mysterious happened.

The research, presented at the European Planetary Science Congress — Division for Planetary Sciences Joint Meeting 2019, notes that Venus potentially had stable temperatures and was home to “liquid water” for 2 billion to 3 billion years, until a “dramatic transformation” started happening more than 700 million years ago that completely reshaped the planet and resurfaced approximately 80 percent of it.

“Our hypothesis is that Venus may have had a stable climate for billions of years. It is possible that the near-global resurfacing event is responsible for its transformation from an Earth-like climate to the hellish hot-house we see today,” said Dr. Michael Way, the study’s lead author, in a statement.

Coming back to the present day, Venus has a surface temperature of 864 degrees Fahrenheit. However, in the five outcomes that Way and the researchers ran for the study, they found that Venus was able to maintain stable temperature scenarios between minus 20 degrees Celsius (-4 degrees Fahrenheit) and 50 degrees Celsius (122 degrees Fahrenheit) for approximately 3 billion years.

Then something mysterious caused a mass explosion of carbon dioxide on the planet between 700 million and 750 million years ago, an event that Way believes could be linked to the volcanic activity on the planet.

“Something happened on Venus where a huge amount of gas was released into the atmosphere and couldn’t be re-absorbed by the rocks,” Way added.

“On Earth, we have some examples of large-scale outgassing, for instance, the creation of the Siberian Traps 500 million years ago which is linked to a mass extinction, but nothing on this scale. It completely transformed Venus.”

Venus is closer to the sun and its extreme surface temperature makes the existence of liquid water on the planet a moot point. But during the simulations, the researchers added an ocean 310 meters (1,017 feet) deep, one that was 10 meters (32 feet) deep, as well as putting some water in the soil.

There was also a scenario where they used Earth’s topography and the 1,017-foot-deep ocean, as well as a planet “completely covered” by an ocean 158 meters (518 feet) deep, and found that even though Venus is closer to the sun than the Earth, liquid water could have been present.

“Venus currently has almost twice the solar radiation that we have at Earth,” said Way.

“However, in all the scenarios we have modeled, we have found that Venus could still support surface temperatures amenable for liquid water.”

Whether it was the planet’s volcanic activity or something else, Venus is now too hot to be supportive of liquid water. Way said more research is needed to understand the planet’s history and how it might affect the search for exoplanets, including ones that may hold liquid water.

“We need more missions to study Venus and get a more detailed understanding of its history and evolution,” Way said.

“However, our models show that there is a real possibility that Venus could have been habitable and radically different from the Venus we see today. This opens up all kinds of implications for exoplanets found in what is called the ‘Venus Zone,’ which may, in fact, host liquid water and temperate climates.”

Earlier this month, scientists detected water vapor in the atmosphere of a “super-Earth” exoplanet with potentially habitable temperatures, K2-18b, 110 light-years from Earth.