The red rain phenomenon of Kerala and its possible extraterrestrial origin

A red rain phenomenon occurred in Kerala, India starting from 25th July 2001, in which the rainwater appeared coloured in various localized places that are spread over a few hundred kilometers in Kerala. Maximum cases were reported during the first 10 days and isolated cases were found to occur for about 2 months. The striking red colouration of the rainwater was found to be due to the suspension of microscopic red particles having the appearance of biological cells. These particles have no similarity with usual desert dust. An estimated minimum quantity of 50,000 kg of red particles has fallen from the sky through red rain. An analysis of this strange phenomenon further shows that the conventional atmospheric transport processes like dust storms etc. cannot explain this phenomenon. The electron microscopic study of the red particles shows fine cell structure indicating their biological cell like nature. EDAX analysis shows that the major elements present in these cell like particles are carbon and oxygen. Strangely, a test for DNA using Ethidium Bromide dye fluorescence technique indicates absence of DNA in these cells. In the context of a suspected link between a meteor airburst event and the red rain, the possibility for the extraterrestrial origin of these particles from cometary fragments is discussed.Comment: 18 pages, 15 figures, accepted for publication in Astrophysics and Space Scienc

Parametric Study of Differential Absorption Lidar Systemfor Monitoring Toxic Agents in the Atmosphere

Differential absorption lidar (DIAL) techniques are advantageously used these days fordetecting and monitoring traces of toxic agents located at several kilometer in the atmosphere.A theoretical study has been carried out to simulate the performance of a multiwavelength DIALsystem. Clouds of hydrazine, unsymmetrical dimethylhydrazine (UDMH), andmonomethylhydrazine (MMH), located at various ranges up to 5 km in the atmosphere, havebeen taken as examples of the toxic agents. It has been shown that a given lidar system cannotdetect any of these agents with a specific cloud thickness if the concentration of that agent isbelow a certain value (Nmin). It has also been shown that if the concentration level of a givenagent is above a certain value (Nmax) at a particular distance, this value cannot be quantified fora given lidar system although the identity as well as the location of that agent can still bedetermined. Further, for some typical parametric conditions, the required energy levels of thelaser to detect specific concentrations of these agents at different distances have been computed.Power levels of the return signals and the SNR values from different ranges have also beencalculated for each of these toxic agents for a given value of the laser transmitter energy

LIDAR for Detection of Chemical and Biological Warfare Agents

Remote detection of chemical and biological warfare agents and toxic gases in the atmosphere is of current interest to both the military and civilian agencies. Out of all currently available techniques, no single technique provides efficient detection against such threats at significant standoff distances. Light detection and ranging (LIDAR) technologies, based on the transmission of laser pulses and analysis of the return signals, have demonstrated impressive capabilities in remote detection of such toxic chemicals. LIDAR is a highly sensitive tool to detect the extremely low concentrations of various toxic agents present in the form of thin clouds at distances of few kilometer. The detection of these toxic clouds is based on the approach of first detecting and measuring the range of the clouds using the scattering phenomena and subsequently identifying the composition of toxic clouds using absorption and fluorescence phenomena. Laser Science and Technology Centre (LASTEC), Delhi has been working on the design and development of LIDAR systems for detection of chemical and biological warfare (CBW) agents. In this paper, theoretical analysis of differential absorption LIDAR (DIAL) for detection of chemical agents and fluorescence LIDAR for detection of biological agents has been discussed. For some typical parametric conditions, the received power levels from different ranges to detect specific concentrations of chemical or biological clouds have been computed and discussed. The technical details of the indigenously developed backscattering LIDAR, which detects and measures the distance of cloud layers up to 5 km is also presented.Defence Science Journal, 2011, 61(3), pp.241-250, DOI:http://dx.doi.org/10.14429/dsj.61.55

Design Analysis of Mid IR DIAL System for Detection of Hazardous Chemical Species

Nowadays, both military and public agencies are concerned with the remote detection of toxic gases and chemical warfare agents in the atmosphere. A promising method for the remote detection of such harmful chemicals in the atmosphere is Differential Absorption Lidar (DIAL). In the current paper, system design analysis has been carried out to build a DIAL system for the detection of toxic chemical warfare agents, chemical warfare simulants, explosive precursors, and pollutants. The proposed DIAL system comprises an Optical Parametric Oscillator (OPO) based tuneable laser, a 203 mm diameter Cassegrain telescope, a TE-cooled MCT detector, suitable data acquisition hardware, etc. The DIAL output parameters like return signals, SNR, and minimum measurable concentrations have been simulated under different weather conditions such as clear sky, moderately hazy sky, and hazy atmospheric conditions for given system input parameters (pulse energy, detectivity, bandwidth, DAQ resolution, etc.). We have considered chemicals such as Sarin, Thiodiglycol (TDG), acetone, and methane to be detected using the system. Analysis has been carried out for these chemicals present at different locations with varying concentrations. Our analysis reveals that the DIAL system with a laser transmitter of 5 mJ energy and 203 mm receiver telescope is capable of detecting a few ppm concentrations of toxic chemicals present anywhere between the ranges from a few tens of meters to 2 km with topographic target present. The sensitivity of the system in terms of minimum detectable concentrations for the considered chemicals is also estimated for different atmospheric conditions. It is seen that the minimum detectable concentration of TDG is 3.2 ppm in clear weather conditions which increases to 9.2 ppm under a hazy atmosphere. A similar analysis has been carried out for other toxic chemicals and has been discussed in the paper

Characteristics of cirrus clouds observed at a low latitude tropical coastal station, Trivandrum using lidar

278-285High altitude cirrus clouds at about 1-2 km below the tropopause were observed using the multiwavelength lidar system located at a tropical coastal station, Trivandrum (8°33'N, 77°E). Seasonal variations of these clouds were studied over a period of one year. The clouds were seen almost 50% of the time of lidar operation. An analysis of lidar data has shown frequent occurrence of such clouds near the tropopause. Based on their optical depth, cirrus clouds were c1assitied into two categories, namely thick cirrus (optical depth > 0.03) and thin cirrus (optical depth < 0.03) and their occurrence frequencies were about 64% and 36% of the total occurrences

Lidar observations on atmospheric dust transported from south-west Asia to Indian west coast region: A case study of colour rain event occurred during July 2001

158-165A dust storm, which originated in the dust bowl of Arabia, Iran, Afghanistan, Pakistan and north-western of parts of India during the month of July 2001, had lifted large quantities of dust into the atmosphere and got transported over long distances. The region on the west coast of India had experienced the interesting phenomenon of ‘‘colour rain’’ due to this dust loading. A typical dust layer had been detected in the lower troposphere using a lidar system located at Trivandrum (8° 33'N, 77°E) during the night of 24 July 2001 prior to the occurrence of colour rain. The lidar measurements indicated that the dust cloud was present in the 4-5 km altitude range with thickness of a few hundred metres. Air back trajectory computed by the HYSPLIT-4 model using NCEP wind data at the 4500 m level clearly indicated that the dust probably had its origin in the south-west Asia, nine days before the event

Solar eclipse induced changes in aerosol extinction profiles: A case study of 11 Aug. 1999 solar eclipse using lidar at a tropical station Trivandrum, India

82-87An experiment has been conducted to understand the 11 Aug. 1999 solar eclipse induced changes in the aerosol extinction coefficient in the troposphere and the lower stratosphere using the multiwavelength lidar system designed and developed in -house at a tropical station Trivandrum (8° 33'N, 77° E). Results of the measurements reveal an increase in aerosol extinction coefficient in the troposphere and a decrease in the lower stratosphere compared to control day. Six high altitude balloon ascents with 1680 MHz radiosonde were conducted from Thumba to study the eclipse induced variations in winds and temperature of the lower atmosphere. The study clearly reveals the cooling of the entire tropospheric layers with maximum of 5°C occurring below 15 km altitude. The changes in the temperature and the relative humidity during the eclipse are the key factors contributed for the observed aerosol extinction coefficient