Steamy Venus-like exoplanet likely oxygen-rich, life-poor
According to new research, a very Venus-like exoplanet known as GJ 1132b might just be the first rocky planet outside our solar system where we detect oxygen in the atmosphere. But ET enthusiasts shouldn't get their hopes up – orbiting extremely close to its star, the sweltering planet's atmosphere likely has a strong greenhouse effect and a magma ocean on its surface.
When it was discovered last year, scientists were intrigued by the possibility that GJ 1132b could sustain an atmosphere. New research, led by astronomer Laura Schaefer, at the Harvard-Smithsonian Center for Astrophysics (CfA), simulated how the planet's history would pan out if it began with an atmosphere high in water content.
Thirty-nine light-years from us, GJ 1132b orbits its red dwarf parent star incredibly closely, at a distance of 1.4 million miles (2.25 million km). By comparison, the sun-hugging Mercury only ever gets as close as 29 million miles (46 million km). At that range, GJ 1132b is bombarded with UV light, which would separate water molecules into hydrogen and oxygen, creating an atmosphere full of water vapor. As a greenhouse gas, that steamy atmosphere would in turn ramp up the planet's heat even further, with temperatures tipping 450° F (232° C).
"On cooler planets, oxygen could be a sign of alien life and habitability," says Schaefer. "But on a hot planet like GJ 1132b, it's a sign of the exact opposite – a planet that's being baked and sterilized."
That steamy atmosphere could be enough to keep the surface rock molten, creating oceans of magma that absorb around 10 percent of the oxygen in the air. While some of it may linger, the vast majority of the oxygen and hydrogen atmosphere would be lost to space. Future studies of GJ 1132b could turn up traces of this leftover oxygen, thanks to next-gen instruments like the Giant Magellan Telescope and James Webb Space Telescope.
"This planet might be the first time we detect oxygen on a rocky planet outside the solar system," says co-author Robin Wordsworth.
GJ 1132b's turbulent origin story sounds remarkably like that of Venus. Our next door neighbor may once have been home to liquid water oceans as well, before they would have boiled away over billions of years and left the desolate desert we know today. While we have theories about what happened to all the oxygen on Venus, the magma ocean-atmosphere model could provide some further clues to its history, and that of similar exoplanets.
The research was published in The Astrophysical Journal.
Source: Harvard-Smithsonian CfA