Venus-like exoplanet has oxygen, but no life

Even if a Venus-like exoplanet discovered last year has an oxygen-based atmosphere, this doesn’t mean the planet can support biological life, researchers from the Harvard-Smithsonian Center for Astrophysics (CfA) cautioned in a new study.

In fact, according to Seeker and the Science Explorer, the opposite might be true in the case of GJ 1132b, a so-called “exo-Venus” that orbits a star 39 light years from Earth. The planet orbits its star at a distance of just 1.4 million miles, meaning it is constantly exposed to high levels of radiation– but somehow it manages to maintain an atmosphere.

Such a planet defies expectations, leading CfA astronomer Laura Schaefer and her colleagues to investigate exactly what kind of atmosphere GJ 1132b has – a thick one, or a thin and wispy one. Based on their assumption that the planet has a water-rich atmosphere, they believe the latter is the case, as they explained in research set to be published in The Astrophysical Journal.

“On cooler planets, oxygen could be a sign of alien life and habitability. But on a hot planet like GJ 1132b, it’s a sign of the exact opposite – a planet that’s being baked and sterilized,” Schaefer explained in a statement. That’s because the ultraviolet (UV) radiation emitted by its host star is causing molecules of water vapor in the atmosphere to break into hydrogen and oxygen.

Findings could shed new light on the evolution of Venus’ atmosphere

Since hydrogen is lighter, it can escape into space more easily, while the heavier oxygen remains behind. In short, the researchers explain, the presence of oxygen in the atmosphere suggests that it was originally water vapor, a greenhouse gas. The presence of atmospheric water vapor would then cause the planet’s already intense surface heat to become even more hellish.

During the earliest stages of GJ 1132b’s atmospheric development, the water vapor would have amplified the UV radiation enough to cause the planet to remain in a molten state for a period of several million years, Schaefer’s team explained. While the magma would absorb some oxygen, and most of it would have escaped into space, at least some would have remained.

“This planet might be the first time we detect oxygen on a rocky planet outside the solar system,” said co-author Robin Wordsworth from the Harvard Paulson School of Engineering and Applied Sciences. If there is any oxygen remaining on this exo-Venus, astronomers will need to use next-generation equipment such as the James Webb Space Telescope to search for and study it.

By studying GJ 1132b and its magma ocean-atmospheric model, the CfA team hopes to be able to learn more about how Venus’ unusual atmosphere originally evolved. Like GJ 1132b, Venus is believed that have once had a water-rich atmosphere, but exposure to the sun’s radiation over time has caused it to be broken down through a process known as “photodissociation.”

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Image credit: CFA/DANA BERRY/SKYWORKS DIGITAL

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