A world of ad­vice is is­sued for sci­en­tists look­ing for alien life

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It’s one of the big­gest ques­tions there is: Are we alone in the uni­verse?

NASA sci­en­tists in the field of as­tro­bi­ol­ogy are look­ing for an­swers. A new re­port from the Na­tional Acad­e­mies of Sciences, En­gi­neer­ing and Medicine has some ad­vice to help them along.

Here are some of rec­om­men­da­tions. its

If you were to look at Earth from space with an ex­tremely pow­er­ful tele­scope, the signs of life would be ob­vi­ous: Trees clus­tered in rain­forests, herds of ele­phants roam­ing across the sa­vanna, the dis­tinc­tive col­ors of al­gae blooms on the wa­ter.

But there’s also plenty of life be­neath the sur­face. Con­sider the soil mi­crobes that pro­duce nat­u­ral an­tibi­otics, or the gi­ant tube worms (they’re ac­tu­ally mol­lusks) that thrive on the freez­ing ocean floor, fu­eled by hy­dro­ther­mal vents in­stead of light from the sun.

Other worlds that may look dor­mant on the sur­face could har­bor life in their in­te­ri­ors.

Ence­ladus, Saturn’s sixlargest moon, is a prime ex­am­ple. Its frozen ex­te­rior may give the im­pres­sion that it’s noth­ing more than a gi­ant ice cube.

But you can’t judge a world by its outer shell. NASA’s Cassini space­craft re­vealed that Ence­ladus has a briny sub­sur­face ocean with com­plex or­ganic mol­e­cules. That, along with heat gen­er­ated by tidal forces, makes sci­en­tists think that the moon could be hos­pitable to life.

If as­tro­bi­ol­o­gists de­tect ev­i­dence of life, how would they know? Are there cer­tain es­sen­tial fea­tures that any form of life must have? Are some of them unique to liv­ing things?

In sci­ence-speak, the thing as­tro­bi­ol­o­gists are look­ing for is a “biosig­na­ture,” a de­tectable sign that life is (or was) present. It may be a par­tic­u­lar shape that only a liv­ing be­ing could pro­duce. It may be a pat­tern of chem­i­cal com­pounds that must have had a bi­o­log­i­cal ori­gin.

There is still much de­bate about what would qual­ify as a biosig­na­ture. The re­port rec­om­mends that as­tro­bi­ol­o­gists buckle down and fig­ure this out.

One pos­si­bil­ity for de­tect­ing life is to fo­cus on biosig­na­tures in ex­o­planet at­mos­pheres. In the last decade, new tech­nolo­gies have greatly im­proved sci­en­tists’ abil­ity to an­a­lyze the con­tents of th­ese dis­tant at­mos­pheres, and NASA should do what it can to ac­cel­er­ate this work, the re­port said.

It’s also im­por­tant to look closer to home. Po­ten­tial biosig­na­tures from some of Earth’s old­est sed­i­men­tary rocks can pro­vide sci­en­tists some­thing to prac­tice on.

When NASA sends ro­botic ex­plor­ers into space, they should be ca­pa­ble of an­a­lyz­ing DNA and RNA with great pre­ci­sion.

An­other im­por­tant con­sid­er­a­tion: Any tech­nolo­gies used on other worlds should tread as lightly as pos­si­ble. And no mat­ter what, they should not con­tam­i­nate any other part of the uni­verse with life from Earth.

And they shouldn’t wait to be con­sulted un­til af­ter key de­ci­sions are made — as­tro­bi­o­log­i­cal fac­tors should be baked in from the very be­gin­ning, when a mis­sion is still in the con­cep­tual stage.

Peo­ple with ex­per­tise in as­tro­bi­ol­ogy should re­main in­volved at every step of the way. That in­cludes the op­er­a­tional phase, when a space probe is ac­tu­ally car­ry­ing out its as­signed work.

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