Our home planet earth has low concentration of ozone in its atmosphere, protecting it from UV radiation, could Exoplanets share the same method but have a different gas in the atmosphere which has a similar role of absorbing UV radiation?

  • $\begingroup$ I couldn't substantiate my claims, comment removed. $\endgroup$ – Magic Octopus Urn Sep 17 '19 at 19:35
  • $\begingroup$ Practially any atmospherical component with a high UV absorbtion does it. It does not need to have such a self-regenerative mechanism than of the Earth. $\endgroup$ – peterh Sep 17 '19 at 19:47

We do not have to look very far from Earth to find evidence for alternative UV absorbers. Something seems to be present in the atmosphere of Venus. While the UV absorber is not yet known and requires more study of the Venusian atmosphere to find out, a couple of ideas published in journals suggest possible alternatives on Venus or elsewhere.

Ferric chloride

Ferric chloride is a known minor constituent in the Venusian atmosphere, and in Icarus a solution of this compound in sulfuric acid is proposed as the UV absorber. The authors favor ferric chloride over an alternative hypothesis involving sulfur aerosols, since the latter are not properly placed in the atmosphere to match observed data. However, sulfur-bearing material need not be dismissed entirely, as we shall see presently.

Disulfur dioxide

This compound, $\text{S}_2\text{O}_2$, is proposed in Geophysical Research Letters as the UV absorber, based on computer models. The authors admit that thus hypothesis requires further modeling (and implicitly, data from exploration that more rigorous models might need) to be developed further.

Finding out what happens on Venus could give a clue to UV absorption mechanisms in other planetary systems as well.


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