Kas Marsil on elu?

Is There Life on Mars?

Enne esmaspäeval sond käivitas Euroopa Kosmoseagentuuri, me vaatame tagasi sajanditevanust ajalugu search kogu eluks Marsil

Powered by Guardian.co.ukSee artikkel pealkirjaga “Kas on elu Marsil? ExoMars Trace Gas Orbiter kulub otsing” kirjutas Stuart Clark, jaoks theguardian.com reedel 11. märts 2016 08.00 UTC

Käivitamine Euroopa Kosmoseagentuuri (ESA) ExoMars Trace Gas Orbiter kosmoselaev esmaspäeval 14 Märts on oluline moment kosmoseuuringutes. See tähistab uut algust otsida elu Marsil.

Huvi elu Marsil ulatub tagasi sajandeid. 17. sajandi hollandi astronoom Christiaan Huygens spekuleerinud oma raamatus Cosmotheoros umbes vajalikud tingimused elu. Ta ei näinud põhjust, et Mars või teistel planeetidel ei saa asustatud.

Ta kutsus elanike Planetarians "ja andis arvamuse, et nende kõrgus oleks dikteeritud suuruse planeedi, et nad olid piisavalt suured, et liikuda koos kergusega - nii nagu meie Maa.

18. sajandil William Herschel õppis Mars, märkides ere polaaralade ja eeldades, et tumedad planeedil olid ilmselt merede. Ta arvas, et Maa ja Marss oli mõnevõrra sarnane, kirjalikult Philosophical Transactions Royal Society, et Marsi elanikud "tõenäoliselt on olukord sarnane meie oma."

Sajand hiljem, Astronoomid olid mõelnud midagi. Teleskoobid paranesid kogu aeg ja astronoomid nähes, mida tundus olevat otse tume jooni, mis ühendavad tumedad "mered".

American astronomer Percival Lowell popularised the notion that these were canals. Mars was mostly desert, he thought, and these canals were the last ditch efforts of a civilisation fighting to irrigate their dying world.

The idea provided inspiration for HG Wells and his novel The War of the Worlds, in which the Martians abandon their fight at home and invade Earth instead.

It is now thought that the ‘canals’ were optical illusions produced by slightly inferior telescopes. As soon as technology improved, the lines were never seen again.

By the 20th century, analysis of Mars’ atmosphere showed that there was hardly any water vapour present, and this put paid to the idea that there were large bodies of water there. The arrival of the first spacecraft in the 1960s showed that there had been water in the distant past and this eventually led to our current ideas that microbial life could have formed billions of years ago and that perhaps some is still clinging on.

In the late 1970s, Nasa’s two Viking missions touched down on the planet. Each lander contained a biological laboratory capable of performing four different experiments that could reveal life. Although the Labeled Release experiment gave initially positive results, it failed when repeated.

The other three experiments showed only negative results and so officially Nasa declared that no life was detected. Controversially, some scientists continue to claim that the initial success of the Labeled Release experiment should be treated as proof of life.

Regardless of such claims, Nasa have been moving away from looking for life on Mars. selle asemel, they have concentrated on investigating the evidence that Mars was once more Earth-like with flowing water and a thicker atmosphere.

The latest twist began serendipitously in 2003. Esa’s Mars Express spacecraft made a tentative detection of methane in the planet’s atmosphere. Methane is a short-lived gas, and on Earth it is produced mainly by lifeforms.

Sisse 2014, Nasa’s Curiosity rover also detected whiffs of the gas. This increased speculation that perhaps there were microbial communities still alive on Mars, producing the gas. The recent detection of running water on Mars also upped the stakes.

Aga, there is also the chance that the methane is produced by geological processes.

Esa’s ExoMars Trace Gas Orbiter is designed to find out which of these options is the most likely. It will look for the gas with unprecedented sensitivity and map its distribution across the planet over a number of years. If anywhere is particularly rich in methane production, that will be a natural target for further investigations.

On which note, Esa is sending the ExoMars rover to Mars’s surface sisse 2018. It will be equipped with instruments capable of detecting the signs of past and present microbial life.

The long search for life on Mars continues

Stuart Clark is the author of The Unknown Universe (Head of Zeus), and co-host of the podcast The Stuniverse (Bingo Productions).

guardian.co.uk © Guardian News & Media Limited 2010

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