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This has reference to the Editorial "Extra terrestrialimpacts" appearing in the August 2004, issue of yourjournal. Let me first thank Dr. Radhakrishna for his kindwords about my work on natural disasters in ancientIndia.In his article, Dr. Radhakrishna makes reference to

regionsofGujarat,Kutch andwesternRajasthan deservingcareful ground survey for evidence of extra terrestrialimpacts.Apartfromindicatingmineralresources, studyanddating of such impact craters would be of help in sortingout some questions of history. A vexed question, stillhaunting us, is the long hiatus between the end of urbancultures circa 1500 BC and the rise of Magadhan citiescirca500Be. What caused this millennium longdark age?It is generally held that the Indus valley civilization, moreappropriately the Sarasvati-Sindhu civilization, collapseddueto severetectonic upheavals. It isintriguing tonote thatas per our ancient literature these upheavals were possiblythe results of extra terrestrial impacts. In this connection,a series of articles written by Mandelkehr in Chronologyand Catastrophism Review should be of interest. Hepresents archaeological, climatological, geologicalevidences for what he calls an Earth-wide event at around2300 BC. He draws our attention to large-scale climaticchanges at 2300 BC including significant global drop intemperature and crustal phenomena occurring at that timecausedby glacial build up and consequent crustal loading.Hisconclusionis that something importanthappenedat thattime that warrants our attention. He has synthesized morethan 250 primary references spanning several scientificdisciplines to arrive at the above conclusion. What couldhave been the root cause' of this earth-wide event?Mandelkehr(2002)tracesthis tothe likelihoodof an intenseencounterof earthwith the Taurid meteoroid stream.Now,it wouldbe interesting to seewhat astronomers have to sayon thepossibilityof such an encounter.Bailey,ClubeandNapier (1990),authorsof amonographon theoriginof comets remark, "Availablerecords indicatethat comets and comet related phenomena seems to haveplayed an important part in the beliefs and social habitsof most known civilizations from the very earliest times."They drawourattention to the evidence ofa necklacemadeof iron-meteorite beads placed in an Egyptian pyramiddating back to 3000 BC. They raise the question whether;

decline of interest with comets in Greek astronomy isrelated to corresponding decrease in observed meteoriticactivity. They forcefully remark - "The final picture thatemerges, therefore, is onewhich duringa veryearly period,prior to the second millennium BC, Man's knowledge ofthe pervading celestial environment gave him a relativelyaccurate understanding of comets and their potentialities."Even though these authors do not seem to be aware ofdevelopments in Indian astronomy, the parallels cannot bemissed. Siddhantic astronomy, which peaked during6-8thcentury AD, ignores comets. VarahaMihira (5_6thcentury) no doubt has included a chapter on comets in hisBrhat-samhita.But, he is frank enough to admit that he iswriting only the views of his predecessors. He quotes theperiodicities of some of the comets, but is categoricalthat their orbits are beyond mathematics. One of hispredecessors, V~ddhaGarga, who perhaps lived in thefirst millennium BC, boldly states that like the star-circlerepeating itself in the sky, the comet-circle also repeats inthe sky. (nak.ratra-cakram iikiise yathaiva parivartate;ketu-cakram tathaivedam iikiise parivartate).ParaSara,whoseworksare knowntous fromlaterwriters,providesa comet classification scheme,gives approximatepositions of comets in the skywith respect to stars and alsotheir return periods. Why was there so much interest inancient India about comets? Was it because, they were afewtoo many andbrought destructionon ground? It issaidthat cometRasmi-Ketu rising in the star cluster ofPleiadeswould destroy Madhya-desa (Central Country) includingKosambi, Avanti, and Pushkaran. If there were to be noconnectionbetween comets and terrestrial impacts, didourancients invent such correlation purely out of theirfertile imagination? The astronomical framework, forunderstanding Earth as a bombarded planet, is providedin a series of papers by Clube and Napier (1984), Clubeet al. (1996), Bailey andNapier (1999) andNapier (2003).Napier (1998) in a paper addressed to non-specialistswrites: "Modern astronomical evidence does not supportthe common supposition that the night sky has beenunchanging for 5,000 years. Occasional disastrousinundations and the raining of fire from heaven arereasonable expectations from the current astronomicalevidenceThe celestial fireworks in thenight sky,especiallyin the formof annual fireball storms, would then be of an

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intensity quite outside that of modem experience. It is likelythat for periods of centuries or millennia one or two cometfragments would dominate being bright, recurring objectsin the night sky. Comet splitting and even multipledisintegration would be a common observed phenomenon.If such a disruption had happened within historical times, itis difficult to imagine pastoral societies remaining indifferentto this annual show. In fact, the most active recent phase ofthe Taurid progenitor comet appears to have been about3000 Be. Conservative estimates have the short-periodprogenitor at that time brighter than Venus. Thus the nightsky around 3,000 BC, and for a period of at least centuriesand probably one or two millennia after it, was disturbedThere are likely too to have been epochs when the skycontained one or more visible, periodic comets, associatedwith annual fireball storms of huge intensity and perhaps

BAILEY, CLUBE, S.V.M. and NAPIER, WM. (1990) The Origin ofComets, Pergamon Press, Oxford. .

CLUBE, S.V.M. and NAPIER, W.M. (1984) The microstructure oftenestrial catastrophism. Monthly Notices, Roy. Astron. Soc.v.211, pp.953-968.

CLUBE, S.V.M., HOYLE, F., NAPIER, W.M. and WICKRAMASINGHE,N.C. (1996) Giant Comets, Evolution and Civilization.Astrophysicsand Space Science, v.245, pp.43-60.MANDELKEHR,. (2002) 'Commemoration of the 2300 BC

827also with devastating impact. Such phenomena, enduringfor centuries, surely had a profound effect on the minds ofearly peoples. At a minimum, traces of this ancient skyshould still be detectable in the artefacts and belief systemsof the earliest cultures."

Dr. Radhakrishna's call for conducting surveys forlocating and dating impact craters in the subcontinent is verytimely. It is hoped that our scientific institutions specializingin Space, Earth and Marine Sciences would take up thisresearch seriously.

Dept. of Civil EngineeringIndian Institute of ScienceBangaLore -560 012Email: rni@civiL.iisc.ernet.in

R.N. IYENGAR

References~ event'-; Chronology and Catastrophism Review, V.2,pp.3-14.

NAPIER,WM. (1998) Cometary Catastrophes, Cosmic Dust andEcological Disasters in Historical Times: the AstronomicalFramework'. in: Peiser, Palmer and Bailey (Eds.), NaturalCatastrophes During Bronze Age Civilisations. Archaeopress,Oxford, England, pp.21-32.

NAPIER,W.M. (2003) 'Giant Comets and Human Culture'Astrophysics and Space Science v.285, pp.513-520.

WHITHER FIELD GEOLOGY?

(1)It is gratifying that Dr. Pronab K. Banerjee blew the

conch through his note entitled 'Whither Field Geology'(JGSI, v.64, no.3, p.367), at the right time, to save 'FieldGeology' from slipping into oblivion. Diminishing(vanishing?) field inputs, increasing patronage to fancifuljargon-ridden hypotheses (probing into the past only) thatmystify more and inform less, and undue enthusiasm totransgress into others' domains are the three major evilsthat plaguethe geological sciences today.Relyingmore onlaboratory data than on field data in dealing withgeoscientificproblems-sometimes to theextent of ignoringeven the mandatory field inputs-would only erode thecredibility of geosciences. Trying to tackle geoscientificproblems sitting in air-conditioned laboratories is asJOURGEOLSOC.INDIA, VOL64. DEC: 2004

ridiculous as trying to seed the clouds sitting before acomputer. The sooner the authorities realize that thereisno substitute to fieldwork, thebetterthey help thesocietyin effectively utilizing geosciences for tapping hiddenmineral wealth. Hopefully, Dr. Banerjee's note wouldserve as a wake-up call to spur the authorities intoaction.FLat # 202, 'Naimisam'Srinagar Colony P.O.Hyderabad - 500 073

P.K. RAMAM

Flat # 401, Srinilaya EstateAmeerpet, Srinagar Colony P.O.Hyderabad - 500073

K.S.RAO