A couple billion years ago, Venus may have looked a lot more similar to how Earth looks today.

According to Matthew Weller, an institutional postdoc at UT’s Institute for Geophysics, along with researchers from Rice University and the University of British Columbia, Venus may have been habitable more than two billion years ago. The groundbreaking research comes with some caveats; Weller said the team’s findings do not suggest that life definitively existed on Venus, but rather that the conditions needed for water and life to exist were once present in Venus’ history.

“We’re very careful not to say life definitely existed,” Weller said. “However, there is a high potential for liquid water to once have been stable for a period of time long enough to sustain life forms.”

He added that the right conditions to allow life to develop may have been headlined by a shallow ocean and temperatures way less than the 850 degrees Fahrenheit the planet sees today. When looking for possible extraterrestrial life similar to life on Earth, scientists generally look for planets that could support liquid water.

“Venus, being much closer to the Sun than Earth (is), is much warmer than our planet,” Weller said. “Based on the fact that the Sun was, at a point, around 30 percent less luminous than it is now, Earth-like temperatures may have been possible early in Venus’ history.”

These findings, presented last month at the Lunar and Planetary Science Conference in The Woodlands, Texas, could also shed light on Earth’s future. According to Weller, the conditions currently characteristic of Venus may reflect what Earth looks like in a billion years.

Researching Venus helps scientists to understand how and why Venus diverged from Earth. Central to this, Weller said, was the difference in tectonic states between Venus and Earth. According to Weller, plate tectonics, the atmosphere and the surface of a planet all work hand in hand to promote the conditions unique to every planet. The fact that conditions were suitable for life to have potentially existed on a planet so different from Earth opens up possibilities for finding life on extrasolar
planets, Weller said. 

“The potential for finding liquid in different tectonic states opens the door for finding life in (other) solar systems,” Weller said. “Habitability might have been easier at a point in time (and) then gotten progressively harder. In this, there is a temporal aspect to habitability.”

Researchers determine whether a celestial body is within the habitable zone to figure out whether liquid water could exist, or could have existed, on a planet. Weller said the team’s findings suggest that scientists should look outside of this habitable zone to find life.

“The potential for habitability on Venus shows that the definition of habitability should be redefined,” Weller said. “Planets are not inhabitable solely due to their location to the nearest host star.”

Weller emphasized that these findings are important to more than just understanding the history of Venus. He said that expanding the definition of habitability means that astronomers can cast a wider net when looking for extraterrestrial neighbors.

“One very important conclusion we have reached is that we can have planets much closer or further to Sun-like stars than we originally thought,” Weller said. “When when we look at extrasolar planets, it could be much easier to find conditions suitable for life.”