Wemay alreadyhavefoundlifeon Mars.
Wejustfailed torealiseit.
In July1976, two NASA Vikingprobes
landed on Mars,onamission to discover
life on theRedPlanet.More than 40
years later,Gilber tLevin still believes
that missionwas asuccess.This is
remarkable because Levin is not an
obscure character on thescientificfringe,
but the NASA scientist who designed one
of the cruciallife-detectionexperiments in
the firstplace.
Levin’s experimentwasbased on a
technique called‘labelled release’. A
sample of Martian soilwasmixed with a
dropofnutrient solution. The nutrients
had been‘labelled’bysubstituting
radioactive carbon-14 for normalcarbon.
If therewereany bacteria intheMartian
soil, they would metabolise thenutrients
and produce carbondioxide containing the
special carbon-14.
To the experimenter’s surprise,the
experimentimmediately producedasteady
stream ofradioactivecarbondioxide.The
sameexperimentwascarried out by both
landerswith thesame result.Apositive
testfor life shouldhave signalledtime to
uncorkthe champagne, butany chance of
celebrationwasquicklyextinguished by bad
news from the other twoexperiments.
The pyrolytricrele ase experiment tested
for organismswhich,likeplant s, turn carbon
dioxide intocarbohydrate.This found no
signof activity.The gaschromotograph-
massspectrometer,orViking Molecular
Analysis Experiment, could identifythe
smallesttraces of organic molecules,
pickingupevenafew partsper billion. But
there wasless carbon in Martiansoil even
than inthelifeless Moonrocksbrought
back by Apollo astronauts.
WhileLevinwas ready to declare
success, his colleagues reachedadifferent
conclusion.To them, the onlyexplanation
that made sensewasthat some non-
biological processwasresponsiblefor
the positiveresult in the labelledrelease
experiment.Apowerful,unexpected
oxidisingagent in the Martian soilmight
account for thecarbondioxide.Further,
when theexperimentwasrepeatedaweek
later ,itcameback negativeonbothlanders.
Later,scientists theorised that the result
wasdue to conditions on the Martian
surface. Marshasathin atmosphere
comparedto Earth, andnoozonelayer, but
it is further from theSun. As aresult,the
overall level of ultraviolet light issimilarto
Earth’s,but it isconcentrated at the short-wavelength, damaging end of the spectrum.
Anyone livingon Marsis goingtoneed
seri ous sunblock; more importantly for the
scientists,thisintenseUV turnscompounds
in exposedsoil int ooxidisers.The 2008
Phœnix missiondiscoveredthe presence of
perchlorates,oxidising chlorine compounds,
in Martian soil. That seemed to settlethe
matter. The labelled release resultwasa
falsepositiv e. Therewas no lifeon Mars.
GilbertLevin,however,has always
remained convincedthat thepositiveresult
from hisexperimentwasvalid.Andhehas
increasingly good reasontobelieve in it.
“Life onMars seemedalongshot,”Levin
wrote inScientificAmericanin October
2019 .“On theother hand, it would takea
nearmiracle forMars tobe sterile.”
ThisisbecauseEarthand Mars have
been, as Levinputsit, ‘swapping spit’
formillions ofyears.Wheneveralarge
meteoritehitsone of theplanets, it throws
up asignificantamount of materialinto
space,knownas ejecta.Atinyamount
of Earth ejectaends up onMars–and
vice versa. TheVikingmission allowed
scientists toexamine the isotoperatios
in Martian rocks so thattheycould be
uniquelyidentified.By 2000atype of
meteorite knownas SNCwasconfirmed
as having originatedfrom Mars. By 2019
over 200 meteoritesfound on Earthhad
beenconfirmed as beingMartian. Asimilar
amountoft errestrialmaterial is likely tohave gone the otherway. Soiltypically
containsaboutabillionbacteria per
gram,giving agood chanceof cross-
planetary contaminationbymicrobes.
Meanwhile,mathematicalanalysis
of the labelledreleaseexperiment data
by ateam attheUniversityofSouth ern
Californiasuggestedthatitdid have
the signatureof life.“All thebiological
experiments fromEarthsorted with the
activeexperiments fromViking,and all
the nonbiological data seriessorted with
the controlexperiments,”said biologist
JosephMiller.“It wasanextremelyclear-
cut phenomenon.”
Thissort of statistical data is
suggestive,but not conclusive, like
the other factors Levincites which have
emergedsinc ethe Viking experiment.
These include evidence of ice,methane
in theMartian atmosphere,and spectral
analysesfrom VikingshowingMartian
rockswith patchesthat correspond to
Earth lichens.Fort eanswill also be pleased
to learn that he mentions as evidence of
life “ghost-likemoving lights,resembling
will-o’-the-wispsonEarth that are formed
by spontaneous ignitionof methane.”
Earth’swillo’t he wisp isacomplicatedand
controversial phenomenon initsown right
(seeFT370:14).
Levin’s maincomplaint is that there has
been no follow-up to hisexperiment.While
subsequent missionshavecarrie dout a
variety of tests,nobody hastried to replicate
the labelled-released results,nor have
they takenthedirect approach of using a
microscope tolookfor the soil bacteria that
it impliedexisted.
NASA’s currentMarsrover ,Curiosity,
has been there since 2012.It has
some impressivesensors,but nothing
correspondingtothe Viking lander
experiments.NASA’sforthcoming 2020
mission willcarrytoolstodrill into theground
and inspect rocks forsigns ofminerals such
as hydrated silicathat, onEarth, areonly
produced by livingthings. Other instruments
will givenew insights on the geology and
climate of Mars.Essentially the2020lander
mightfind fossils, but it could drill rightpast
life withouteverseeing it.
Levin’s frustrationisunderstandable. He
mayvery wellbewrong,and theremay be
otherexplanations for the1973result. But
if he is right, we discoveredlife on Mars
46 years agoand have failed to followup
on theimportantscientificdiscovery of the
century.The Martiansmustbewondering if
we areignoring themdeliberately.Life on Mars?DAVID HAMBLINGasks whether we discovered life on theRedPlanet in 1973 without realising itNASA
12 FT“LifeonMarsseemedalongshot.ButitwouldtakeanearmiracleforMarstobesterile”SCIENCE DAMNED DATA,NEW DISCOVERIES AND RADICAL RESEARCH