Iron rain on WASP-76b

ESPRESSO measurements of varying iron abundances across the ultra-hot Jupiter WASP-76b indicates that iron vapour condenses and rains out over the night side.

ESO Press Release: ESO Telescope Observes Exoplanet Where It Rains Iron

From the paper (pdf) abstract:

Quote :

Here, we report the detection of an asymmetric atmospheric signature in the ultra-hot exoplanet WASP-76b. We spectrally and temporally resolve this signature thanks to the combination of high-dispersion spectroscopy with a large photoncollecting area. The absorption signal, attributed to neutral iron, is blueshifted by -11±0.7 km s^-1 on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside. In contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. Iron must thus condense during its journey across the nightside.

Now on arXiv.
https://arxiv.org/abs/2003.05528