Can the James Webb Telescope distinguish exo-Earths from exo-Venus?

The success of the Transiting Exoplanet Search Satellite (TESS) project in discovering exoplanets orbiting other stars has led a group of four American researchers to question whether we can truly know whether a world is Earth-like just by observing it. It may be possible to distinguish only by atmospheric observations. Our planet is an “oven” similar to our neighbor Venus, With an average temperature of 460°?

To find out whether any of the exoplanets discovered by the MIT/NASA partnership have habitability conditions similar to those on Earth, the authors investigated transmission differences between hypothetical exo-Earths and exo-VenusBoth contain different amounts of atmospheric carbon dioxide (CO2); this is an easily detectable sign of the presence of an atmosphere.

To write their paper, now hosted in the arXiv preprint repository, the researchers pointed a James Webb Telescope (JWST) simulation at the planets. The experiment tested the ability of the NIRCSpec instrument in the real telescope to observe the wavelengths of light reflected from distant worlds.

Simulation of the James Webb Telescope

To test different hypotheses, the simulation placed six Earth-like planets and six Venus-like planets 40 light-years away but with different levels of carbon dioxide (CO2), cloud cover, and haze in their atmospheres. The simulated planetary system orbited a star similar to TRAPPIST-1. It is a cool red dwarf located 39 light-years from the Sun in the constellation Aquarius.

Test planets during simulation their orbits are aligned at the same “runaway greenhouse boundary”, that is, the distance from the star at which a “global catastrophe” could occur, resulting in Venus’ transformation into a hellish planet.

Naturally, different compounds in the atmosphere triggered the spectrometer to allow the chemical compounds to be read. However, these data are not always clear, as the spectral signatures of certain molecules obscure those of others or even mimic them, making the “visibility” unclear.

Difficulties in distinguishing spectral signatures of exoplanets

Elimination of inaccuracies between planets began with the atmosphere, where the presence of CO2 was essential. But when it comes to Earth and Venus, things get complicated because the chemical compound’s signature overlaps with water and methane, confusing the data.

In this case, the difference would be a feature unique to dry planets: sulfur dioxide. The problem is that SO2 does not exist on Venus in real life because UV radiation destroys it.

Therefore, since there is no methane absorption on Venus, a better solution would be to bet that methane would be the defining feature of an Earth-like planet. Additionally, CH4 absorption is spectrally different from CO2 absorption. If methane is accompanied by oxygen, the chance of life is high.

Get up-to-date information about science and astronomy at TecMundo!