Synthesis of the fairy circle emissions characteristics. A. A fairy circle in Brazil showing how the vegetation is affected. B. Variability on time over 5 weeks for a given sensor in the structure monitored in Brazil. See Prinzhofer et al. (2019) and Myagkiy et al. (2020) for details about that case. C. Daily variations for 6 sensors installed on the structure monitored in Brazil showing the 24 h period. D. Variability in size, of the emitting structures in USA (modified from Prinzhofer and Deville, 2015). E. Two profiles across a structure showing the spatial variability of H₂ concentration value between the center and the rim of the structure, Lake Podowoye, Russia. These values have not been taken at the same time but over 2 days. Modified from Larin et al. (2014). F. Profile showing an example of [H₂] concentration variation versus depth in USA (modified from Zgonnik et al., 2015).