A sample of yellow colored rainwater kept in plastic tube and in beaker. The color was more intense during collection but subsequently faded. 

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... number of cases of yellow colored rain occurred in Kerala, India in July-August 2001 along with the red rain phenomenon. Recently during the end of July 2008 a few cases of yellow colored rain again occurred in Kerala and during the same time, unusual rain, termed as “blood rain” occurred in Bagado, Colombia. In this paper we show that the yellow rain and red rain can have a common origin. The yellow rainwater also exhibits the same unusual autofluorescence reported earlier for the cultured red rain microbes. Reasons for considering extraterrestrial origin for these colored rains are discussed. Keywords: red rain of Kerala, Yellow rain, red rain cells, Extraterrestrial life, autofluorescence, Intrinsic fluorescence Yellow rain was first noticed in Kerala during July to Sep 2001 along with the red rain phenomenon . Of the total 124 reported cases of colored rain events, 13 were yellow rain. While the red rain contained a suspension of microscopic red cells the yellow rain contained mainly dissolved components. On the basis of geographical and time distribution pattern of the red rains in Kerala which occurred over the period of July to September in 2001, we argued that the red cells which colored the rainwater may have possibly originated from cometary meteor fragments that disintegrated in the upper atmosphere. A huge explosive sound heard by the residents early in the morning before the first occurrence of the 2 red rain was a possible link to the suspected meteor origin. In a recent finding McCafferty reported that this proposed meteoric origin of red rain of Kerala might be consistent with historical accounts linking red rain with meteor explosion. During the following years after 2001 minor cases of colored rain was also reported in Kerala during the months of July to September. This is consistent with the idea that Earth may be passing through a crossing orbit of color rain causing special meteoric bodies during these months. The colored rain phenomenon is not limited to Kerala. On July 29 in 2002 3 a major event of red colored rain occurred in the central province Nghe An in Vietnam . A colored rain occurred in the 4 municipality of Bagadó, Chocó, Colombia, on 31 July 2008 . Yellow rain was also reported in Kerala in the month of th th th July 2008 in Kottayam. The phenomenon occurred in Kerala on 18 , 25 and 29 July in neighboring places separated by a distance of about 20 km. Sample of this rain was used for the present study. A sample from Colombia could not be obtained but from the description and pictures that appeared in some Internet sites it appears to be the same as what fell in Kerala on the previous days. Kerala and Colombia are near to equator but are on either side of the earth. Meteoric origin is the most likely explanation for the appearance of similar kind of colored rains on subsequent days on either side of the earth. In this paper we show that the Red rain and Yellow rain are related events. The chemicals present in the cultured red rain cells also appear to be present in Yellow rain sample. Details of the study by fluorescence spectroscopy are presented below. The sample used for the present fluorescence study, was collected from the location were the yellow rain occurred in July 2008. The Fluorescence spectra of the yellow rain water were recorded using Shimadzu spectrofluorimeter (RF- 5301 PC, Shimadzu). Emission wavelength was scanned from 300 nm to 900 nm for constant excitation wavelengths of 10 nm intervals. The autofluorescence of the sediments found in the yellow rainwater was visualized in an Olympus fluorescence microscope (BX51) with epi-illumination. Various combinations of excitation and emission filters were employed. Optical and scanning electron microscope images of the sediments were also recorded. Fig 1 shows the image of the rainwater collected from Pallikathodu near Kottayam where yellow rain occurred in 2008. The sample of yellow rainwater contained some minor quantity of sediments, which appeared to be of biological origin. . Figure 2 shows some of the structures found in the yellow rain residues. Most of the residues are a jelly like substance with an appearance of aggregates clustered together (fig 2a & 2b). Also the yellow rain contains structures (fig 2c) with 5 striking similarity with a mother cell of cultured red rain cell . These residues are absorbing various dyes and appear to be of biological. The scanning electron micrograph of the residues is shown in figure 3a and 3b in which fig 3a shows a cluster and fig 3b shows a single particle. The particles were subjected to fluorescence microscopy study. Fig 4a - 4c shows the photomicrograph of the autofluorescence of the sediments found in the yellow rain when excited with UV, blue and green light respectively. 3.2 Spectrofluorimetric study The autofluorescence property of yellow rain was studied more extensively using spectrofluorimeter. The Fluorescence spectrum of the yellow rain was recorded using Shimadzu spectrofluorimeter (RF-5301 PC, Shimadzu). Emission wavelength was scanned from 300 nm to 900 nm corresponding to different excitation wavelengths. The yellow rainwater shows the unusual fluorescence behavior of shifting in the peak of emission wavelength from 438 nm to 535 nm for a shift in the excitation wavelength ranging from 300 nm – 500 nm (fig. 5). Usually the emission peak is supposed to remain constant but here there is a systematic change in the emission peak as excitation wavelength is changed. This unusual fluorescence violates the Kasha’s rule dealing with the theory of fluorescence emission and the reason for this unusual fluorescence behavior is yet to be identified. Among the emission peaks the peak corresponding to an excitation of 370 nm has the maximum intensity. UV excitation in the region 250 - 340 nm causes a double peak to appear due to the merging of two peaks. To resolve these peaks the emission spectrum was de-convoluted using Gaussian de-convolution method and the resulted spectrums are shown in figure 6 for the excitation wavelength 300 nm. The de-convoluted curves clearly show the presence of two emission peaks centered around 385 nm and at 450 nm. The 385 nm emission peak is comparatively of lower amplitude when compared with the 450 nm peak. This small 385 nm peak reduces in intensity as the excitation wavelength is increased and it almost vanishes for excitations beyond 340 nm. The excitation dependant emission wavelength is shown in figure 7, which shows an almost linear dependence in the 300 to 500 nm excitation region. The unusual autofluorescence property of the yellow rainwater and particles found in that are strikingly similar to what 6 we have found for the cultured red rain cells . In a recent investigation we reported the unusual fluorescence behavior of cultured red rain cells, which shows the systematic shift in the fluorescence emission peak as the excitation 6 wavelength is changed, and this intrinsic property is against the Kasha’s Rule in the fluorescence emission theory . It was reported that UV excitation of cultured red rain cell in the region 270-340 nm showed two broad emission peaks which are overlapped and found at 385 nm and at 450 nm respectively after the spectrum were de-convoluted using Gaussian de-convolution method. The 450 nm peak shift to longer wavelengths as the excitation is increased beyond 370 nm. The fluorescence spectra of the yellow rain also behave exactly as the fluorescence spectra of cultured red rain cells. The fluorescence microscopy images of the yellow rain show the autofluorescing behavior under different excitation wavelength, which is also similar to the cultured red rain cells. The yellow rain also contains few structures similar to the mother cells, which was observed in the culturing experiment. Present study showed striking similarities between yellow rain and cultured red rain cells in the fluorescence emission characteristics. From the above studies we can conclude that both yellow rain and red rain are associated phenomenon. On the other way round since both type of rains, red and yellow appear under similar conditions they are associated phenomenon so it shows that what we culture at 300 deg C are indeed the daughter cells of red rain cells. The appearance of colored rain on either side of the Earth on subsequent days shows that meteoric origin is the most likely explanation for the colored rains and the cells associated with these rains are most possibly extraterrestrial ...