Based on what scientists have said about Venus, finding a world similar to it may not seem like a thrilling breakthrough in space research: Our neighboring planet's surface is a hot, toxic world, with sulfuric acid rain and volcanoes.
But Venus might once have been an ocean world much like Earth before it devolved into a hellhole. Now two teams of international scientists have found a Venus-like planet not far from our own solar system, and they're eager to know if it's habitable.
The so-called "exo-Venus," a rocky exoplanet similar in size to Venus, is known as Gliese 12 b, a world just 40 light-years away in the constellation Pisces. Unlike the real Venus, which is about 900 degrees Fahrenheit because of a runaway greenhouse effect, researchers think it could have a much less hostile temperature.
"We've found the nearest, transiting, temperate, Earth-size world … to date," said Masayuki Kuzuhara, an assistant professor at the Astrobiology Center in Tokyo, who co-led one of the teams, in a statement. "Although we don't yet know whether it possesses an atmosphere, we've been thinking of it as an exo-Venus, with similar size and energy received from its star as our planetary neighbour in the solar system."
Scientists discovered the exoplanet using NASA's TESS, short for Transiting Exoplanet Survey Satellite, and the European Space Agency's Characterising Exoplanet Satellite, Cheops. Some of the findings are published in the Monthly Notices of the Royal Astronomical Society.
One year for Gliese 12 b is less than two weeks on Earth. That means it orbits extremely close to its host star. But the cool red dwarf star is about 27 percent the size of the sun, with a surface temperature about 40 percent cooler. Given Gliese 12 b's distance, it gets about 1.6 times more energy from its star than Earth from the sun, according to the research.
Scientists estimate the average surface temperature on an atmosphere-less Gliese 12 b could be about 107 degrees Fahrenheit, which may sound like a summer day in California's Death Valley. Earth's average surface temperature at sea level is just 59 degrees Fahrenheit.
That means in order for people to really know the climate of this uncharted world, they need more information about its atmosphere — or lack thereof. And there's a range of possibilities: It could have conditions similar to Earth's atmosphere, those more like Venus', no atmosphere at all, or a different swaddle of gasses altogether.
Knowing what's in a planet's atmosphere is important for scientists. NASA has playfully called Earth's own atmosphere its "security blanket": Without it, the type of life flourishing here wouldn't exist. This cocoon holds oxygen in the air and filters out harmful ultraviolet radiation, all while keeping our world warm and livable. Furthermore, it creates pressure that allows liquid water to exist on Earth's surface.
Water vapor has been discovered on gassy exoplanets before, but never for a rocky or terrestrial planet akin to Earth, Mars, Mercury, or Venus.
Learning Gliese 12 b's atmospheric conditions could help determine whether this exo-Venus could hold water and potentially support life. Though scientists don't yet know, the James Webb Space Telescope, which can peer into the atmospheres of distant worlds, could soon provide some answers.
