Life, But Not As We Know It - IELTS Reading Answers & Explanations

You should spend about 20 minutes on Questions 28–40, which are based on Reading Passage 3.

Life, but not as we know it

Astrobiology is arguably the trendiest buzzword in science after genomics. Like genomics, it is as hip as it is hard to define. Broadly speaking, it is an umbrella term for the efforts of many scientists working in diverse fields to understand the conditions of life in the universe, whether on Earth or elsewhere.

The canvas is, in fact, so broad that many scientists might be astrobiologists without knowing it: astrobiology adds glamour to all science, from astronomy to zoology. Those with long memories and a cynical mien will have seen all this before. Once upon a time, there was a research programme called exobiology. Is astrobiology a new name for repackaged goods?

No, for two reasons. First, many discoveries made in the past decade have set people thinking, once again, about life elsewhere. For example, hardly a month goes by without the discovery of yet another planet orbiting a distant star. And whatever the truth about the much-disputed claims for fossils in martian meteorites, the controversy has rehabilitated the idea of panspermia: that life can spread between planets.

Second, astrobiology is almost a trademarked term. The Nasa Astrobiology Institute is a virtual campus linking research centres with universities, all devoted to learning more about the general principles governing the origin of life in the universe. Significantly, Nature magazine recently looked at astrobiology in all its forms, from the quest to understand how life began on Earth to the prospects of finding intelligent life elsewhere in the universe.

Not that this should be a cause for wide-eyed celebration, say its critics. Ironically, the most vociferous of these come not from the world of science but from science fiction. Brian Aldiss, veteran writer, critic, and leading light of the genre, dismisses our current obsession with life elsewhere, however much it is justified by science, as an expensively scratched itch.

Aliens, he argues, are a manifestation of a fundamental human urge to populate the universe with 'others', whether gods, ghosts, little green men, or cartoon characters. Scientists should beware of taking science fiction too seriously: aliens are useful as plot devices, but this does not make them real.

A rather different criticism comes from scientists-turned-science fiction writers Jack Cohen and Ian Stewart. Both are academics – Cohen is a biologist, Stewart is a mathematician – but they have worked in SF, most recently on their novel Wheelers. Their argument with astrobiology is not that aliens might not exist, but that we cannot help be constrained in our search.

All organisms on Earth, from the tiniest bacterium to the biggest whales, are constructed according to the same rules. Earthly genetic information is carried in genes made of DNA, earthly life is based on polymers of carbon, and its chemistry happens in liquid water. Because this kind of life is all we know, we tend to think that the same rules need apply everywhere. So, when probes land on Mars, or scientists look at martian meteorites, they tend to look for the kinds of vital signs that betray earthly organisms when we have absolutely no reason for thinking that life elsewhere should be earthlike, or that our definition of life cannot be based more broadly. When the Mars Rover sat and stared at a rock, how do we know that the rock was not staring right back?

It is a fairly simple matter to come up with a definition of life that is based on what it does, rather than what it is made of. It is much more difficult, however, to make such a definition stick, preventing the term from becoming so inclusive as to be meaningless.

You might start by positing three rules. The first is that life requires the existence of information that can be reproduced and inherited, with variation. Second, that living systems seem to create order and structure and maintain it in the face of chaos. Third, that a living system has to work hard to maintain its structure, and as soon as it stops doing this it degenerates.

These rules seem, at first, to be fairly precise, in as much they weed out quietly observant martian surface rocks. But as Cohen and Stewart show in their novel, it is possible to imagine entities that follow all three rules and which appear to be alive, but which bear absolutely no resemblance to terrestrial organisms. In Wheelers, they describe civilizations of floating, methane-breathing balloons in the atmosphere of Jupiter and organisms made of magnetically-confined plasma, living in the outer layers of the sun.

Other science fiction writers have imagined life on the surfaces of neutron stars, inside computers, or even in interstellar space. In his latest novel, Look to Windward, Iain M Banks describes organisms the size of continents, supporting entire civilizations as their intestinal parasites. All could be said to constitute life, but in Dr McCoy's immortal phrase from Star Trek, 'not as we know it'.

Could this mean that astrobiology, the aims of which are universal, is really no more than a parochial exercise? We might never know – perhaps even when we are visited by aliens from the other side of the galaxy who try, frantically, to gain our attention, by waving under our noses whatever it is they wave under such circumstances. It will not be their fault that they will be microscopic and destroyed by a single sneeze. As Cohen and Stewart conclude in Wheelers: 'Life goes on everywhere.'