Morphological and Molecular Analysis Calls for a Reappraisal of the Red Rain Cells of Kerala

Abstract

Early studies on the coloured particles that fell as red rain over southern India identified them as unicellular eukaryotes such as members of the red algae or fungi; however, the results of the present investigation are not consistent with this designation. Using transmission electron microscopy, we have demonstrated significant differences in the ultrastructure when compared with representative species from these other groups. Most notably, the red rain cells show no evidence of typical eukaryotic internal structures such as mitochondria or endoplasmic reticulum. Furthermore, comparisons based on elemental composition using energy-dispersive X-ray analysis, as well as Raman spectral signatures demonstrate significant dissimilarities in their molecular composition. The identity and origins of the red rain cells remain an enigma; however, our findings are more consistent with an unidentified prokaryote, and thus suggest that previous attempts at their identification should be reappraised.

Red Rain Cells of Kerala as a Possible Carrier of the Diffuse Interstellar Bands and the UV Extinction Bump

“…Using transmission electron microscopy, Gangappa et al [33] demonstrated significant differences in the ultra-structure of red cells when compared with representative species from these groups. The red rain cells showed no evidence of typical eukaryotic internal structures such as mitochondria or endoplasmic reticulum.…”

“…The red rain cells showed no evidence of typical eukaryotic internal structures such as mitochondria or endoplasmic reticulum. Also comparisons based on elemental composition using energy-dispersive X-ray analysis, as well as Raman spectral signatures demonstrate significant dissimilarities in their molecular composition and concluded that the identity and origins of the red rain cells remain an enigma [33].…”