Cosmos - - Feature -

bi­o­log­i­cal pro­cesses – most notably pho­to­syn­the­sis. More­over, be­cause it re­acts so read­ily with other mol­e­cules, oxy­gen has to be con­tin­u­ously re­plen­ished to re­main in cir­cu­la­tion. Our own planet clearly sig­nals the pres­ence of life by the fact oxy­gen ac­counts for al­most 21% of the at­mos­phere.

The pres­ence of oxy­gen in a planet’s at­mos­phere, how­ever, is by no means ev­i­dence of com­plex life forms; it can be pro­duced by sin­gle-celled or­gan­isms, like the cyanobac­te­ria thought re­spon­si­ble for the ini­tial oxy­gena­tion of Earth’s at­mos­phere some 2.3 bil­lion years ago. Biomark­ers for multi-celled or­gan­isms are more sub­tle. Whether such sig­na­tures might be de­tectable at in­ter­stel­lar dis­tances is a hot topic in as­tro­bi­ol­ogy. Some pos­si­bil­i­ties do ex­ist: for ex­am­ple, the chloro­phyll con­tent. Veg­e­ta­tion pro­duces a char­ac­ter­is­tic spec­tral pro­file. This so-called ‘veg­e­ta­tion red edge’ is al­ready used to map our own planet’s re­sources from space.

How might we re­act to the un­equiv­o­cal de­tec­tion of rudi­men­tary life be­yond our planet? Whether life ex­ists else­where in space is one of the big­gest ques­tions of our time. Even the dis­cov­ery of sin­gle-celled or­gan­isms would have far-reach­ing im­pli­ca­tions. But the find­ing that re­ally would be over­whelm­ing is un­equiv­o­cal ev­i­dence of an in­tel­li­gent civil­i­sa­tion. The so­cio­cul­tural im­pacts of such a dis­cov­ery would be pro­found. Sci­ence, tech­nol­ogy, ethics, pol­i­tics and re­li­gion – all will un­dergo ma­jor shifts as we come to terms with a com­pletely new per­spec­tive: we are not alone.

The way ELTS might re­veal that knowl­edge is by find­ing so-called tech­no­mark­ers. There are chem­i­cals that can only be in­tro­duced into a planet’s at­mos­phere in sig­nif­i­cant amounts by in­dus­trial pro­cesses. They in­clude well-known of­fend­ers such as chlo­roflu­o­ro­car­bons. Even­tu­ally ELTS should al­low us to de­tect these tell-tale pol­lu­tants in the at­mos­pheres of dis­tant plan­ets. The irony is in­escapable: ex­trater­res­trial in­tel­li­gence dis­cov­ered be­cause aliens were trash­ing their planet, just as we are trash­ing ours.

FRED WAT­SON is the for­mer as­tronomer in charge of the Aus­tralian Astro­nom­i­cal Ob­ser­va­tory. His books in­clude Stargazer: The Life and Times of the Te­le­scope and Star-craving Mad, Tales from a Trav­el­ling As­tronomer.

IMAGES 01 M3 En­gi­neer­ing 02 Univer­sity of Cardiff 03 Gi­ant Mag­el­lan Te­le­scope – GMTO Cor­po­ra­tion 04 ESO / L. Calçada

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