Last year, a distant planet named GJ 1132b was discovered at a distance of 39 light-years from Earth. Although it is being “baked” to a temperatures of around 450 degrees Fahrenheit, astronomers think it likely has an atmosphere.
The nature of this atmosphere has been the subject of a recent study by Harvard astronomer Laura Schaefer and her colleagues. To determine if atmosphere is thin and wispy or thick and soupy, Schaefer and her team presume it started with a steamy, water-rich atmosphere and then tracked what would happen over time.
GJ 1132b is flooded with ultraviolet or UV light as it orbits its star at a mere 4 million miles (for comparison Earth distance from the Sun is 92.960.000 miles). This has the effect of breaking apart water molecules into oxygen and hydrogen. Both of these are eventually lost into space, but as oxygen is heavier, it tends to stay around for longer. If the planet was cooler, oxygen could be a sign of habitability and alien life. With GJ 1132b being so hot however, the exact opposite happens. The planet is being scorched and therefore sterilized, along with a strong greenhouse effect due to the water vapor, intensifying the star’s already concentrated heat. The surface will therefore likely stay molten for millions of years.
The magma ocean would absorb some of the oxygen in the atmosphere although it is not certain how much. Based on the model Schaefer and her colleagues created, as much as 90 percent of the oxygen is lost into space, leaving roughly 10 percent lingering on the planet. Robin Wordsworth from Harvard Paulson School of Engineering and Applied Sciences, and co-author of the paper, believes this is the first time oxygen was detected on a rocky planet outside the solar system. This belief might in future be confirmed by next-generation telescopes like the James Webb Space Telescope and the Giant Magellan Telescope. The telescopes might also be able to analyze the oxygen, if there is indeed any.
The fact that there is no oxygen in Venus’ atmosphere is something that continues to baffle astronomers. It is likely that Venus started with Earth-like amounts of water and although it should have been broken apart by sunlight, there are no signs of lingering oxygen. Schaefer’s new magma-ocean atmosphere model could help scientists solve Venus’ puzzle.
The system TRAPPIST-1 has three planets that are cooler than GJ 1132b. Schaefer hopes that their model will provide insights into TRAPPIST-1 as its exoplanets are similar to GJ 1132b. As the three planets may lie in the habitable zone, they are more likely to retain an atmosphere.
This work has been accepted for publication in The Astrophysical Journal and is already available here.