FEAR OF A BUGINFECTED PLANET

How to stop mi­cro­scopic crea­tures hitch­ing a ride into space? Not eas­ily, it turns out. Aside from be­ing gen­er­ally im­po­lite and per­haps set­ting off an ex­tremely small- scale war of the worlds, con­tam­i­na­tion could make it hard to tell if any life we de­tect

Cosmos - - View Point - KATIE MACK is a the­o­ret­i­cal as­tro­physi­cist who fo­cuses on find­ing new ways to learn about the early Uni­verse and fun­da­men­tal physics.

YOU’D THINK IT WAS the name of a su­per­hero, but the Plan­e­tary Pro­tec­tion Of­fi­cer doesn’t wear a cape or work in a se­cret un­der­ground lair. The most de­vi­ous vil­lains en­coun­tered by NASA’S Plan­e­tary Pro­tec­tion Of­fice are mi­cro­scopic crea­tures that live in pond wa­ter and vaguely re­sem­ble in­flat­able bears. Though the of­fice is tasked with pro­tect­ing Earth from alien threats (for in­stance, from sam­ples brought home from outer space), its pri­mary pur­pose is to save the rest of the so­lar sys­tem from us.

Life is messy. It gets everywhere. On Earth, ev­ery niche we’ve found where liq­uid wa­ter is even in­ter­mit­tently present is pos­i­tively teem­ing with the stuff. Mi­crobes swarm in drops of wa­ter, tiny arach­nids bur­row in your eye­lash fol­li­cles (sorry), and su­per-hardy crea­tures known as ex­tremophiles make their homes in seem­ingly hos­tile habi­tats such as frozen glaciers and deep-sea vol­canic vents.

By flour­ish­ing so well where we’d least ex­pect them on Earth, these ex­tremophiles give us hope for find­ing life in the un­friendly con­di­tions of the outer So­lar Sys­tem. But they also present a prob­lem.

With our in­trepid mi­cro­bial menagerie al­ways present, when we hu­mans build and send out a space­craft to look for life, we risk con­tam­i­nat­ing the very en­vi­ron­ment we’re try­ing to study. Aside from be­ing gen­er­ally im­po­lite and per­haps set­ting off an ex­tremely small-scale war of the worlds, con­tam­i­na­tion like this could make it hard to tell if any life we de­tect is re­ally alien.

This is where plan­e­tary pro­tec­tion comes in. Ar­ti­cle IX of the Outer Space Treaty, drawn up by the United Na­tions’ Of­fice for Outer Space Af­fairs and to which 107 na­tions are party, as­serts that space ex­plo­ration should avoid “harm­ful con­tam­i­na­tion” of other space bod­ies. When­ever an agency such as NASA sends a probe out into the uni­verse, non-con­tam­i­na­tion guide­lines re­quire ster­il­i­sa­tion pro­ce­dures ap­pro­pri­ate to the probe’s ul­ti­mate des­ti­na­tion. The rules are sig­nif­i­cantly stricter for a lan­der than an or­biter, and even more rig­or­ous if the land­ing site is thought to have a high chance of host­ing life. The Plan­e­tary Pro­tec­tion Of­fi­cer over­sees the process.

It can have frus­trat­ing con­se­quences for ex­plo­ration. Plan­e­tary pro­tec­tion is part of the rea­son for NASA plung­ing its Cassini space­craft into Saturn’s at­mos­phere, va­por­is­ing it in a blaze of glory. Cassini was never meant to be a lan­der; but Saturn has moons with liq­uid wa­ter, such as Ence­ladus, that are con­sid­ered some of the best bets for the pos­si­bil­ity of alien life in the So­lar Sys­tem. If Cassini didn’t burn up, it might at some point crash into one of those moons, po­ten­tially wreck­ing what­ever bio­sphere that moon might con­tain.

Sim­i­lar con­cerns have pre­vented any­one from send­ing lan­ders to re­gions on the sur­face of Mars that ap­pear to have in­ter­mit­tent seep­age of liq­uid wa­ter, where chances for life might be high. No mat­ter how hard we try to com­pletely ster­ilise a space­craft, there’s al­ways some chance a tiny Earth denizen might be cling­ing on.

Some of those mi­cro­scopic ex­plor­ers have proven in­cred­i­bly hard to get rid of. The tiny tardi­grade, also known as a wa­ter bear, for ex­am­ple, is an eight-clawed aquatic an­i­mal that grows to a max­i­mum length of about one mil­lime­tre and sort of looks like a cross be­tween a mono­chrome panda and an air mat­tress.

Tardi­grades have long been known to sur­vive ex­treme tem­per­a­tures, hard ra­di­a­tion and even the vac­uum of space. When wa­ter isn’t present, they can shrivel up and wait it out in a dor­mant state for up to a decade, or per­haps – ac­cord­ing to some re­searchers – even cen­turies.

While tardi­grade habi­tats are usu­ally far from space­craft labs, it is con­ceiv­able one could stick to a shoe or blow around on the breeze; and there may be other tiny ex­tremophiles we haven’t yet cat­a­logued hitch­ing rides into space.

When hu­mans even­tu­ally walk on the sur­face of Mars, ster­il­is­ing every­thing will be im­pos­si­ble. It may be that, at that point, all hope of avoid­ing con­tam­i­na­tion will be lost.

In the mean­time, the Of­fice of Plan­e­tary Pro­tec­tion is here to look out for our fel­low cit­i­zens of the cos­mos, even if it does mean we have to say good­bye to our favourite ro­botic ex­plor­ers a lit­tle sooner than we’d hoped.

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