Buổi 122: Reading – Bài khoa học dài nhiều dạng: sự sống ở nơi khắc nghiệt

Life at the edge

(Bài đọc tự viết; nhà nghiên cứu và địa điểm cụ thể là giả định.)

A For much of the twentieth century, biologists assumed that life could exist only within a fairly narrow range of conditions: moderate temperatures, liquid water, sunlight or a supply of oxygen, and an absence of extreme pressure or acidity. Places that fell outside this range – boiling springs, frozen deserts, the deep ocean floor – were assumed to be lifeless. That assumption has since been overturned.

B Organisms that thrive in conditions once considered impossible for life are now known as extremophiles. Most are microorganisms, such as bacteria and similar single-celled life forms. Some live in water close to boiling point; others survive in highly acidic or salty environments, or in rock far below the surface. What unites them is not a single feature but the fact that each has adapted to conditions that would destroy most other forms of life.

C Among the most striking discoveries were communities of organisms living around hydrothermal vents – openings in the sea floor where heated, mineral-rich water emerges from beneath the Earth’s crust. No sunlight reaches these depths, so the organisms cannot rely on photosynthesis. Instead, some microorganisms obtain energy from chemical reactions involving substances dissolved in the water. These microbes, in turn, form the base of food chains that support larger animals.

D Extremophiles are of interest for several reasons. One is practical. Enzymes from organisms that live at high temperatures, for instance, remain stable in conditions that would damage ordinary enzymes, and some have proved useful in laboratory and industrial processes. Another reason is theoretical: studying how life copes with extreme conditions may help scientists understand the limits of biology itself.

E Perhaps the most ambitious interest, however, comes from astrobiology – the study of whether life might exist beyond Earth. If life can survive in boiling water, frozen ice or deep rock on our own planet, it is at least possible that similar environments elsewhere could support some form of life. Several moons in our solar system are thought to have liquid water beneath icy surfaces, and it has been suggested that conditions there may resemble those around hydrothermal vents. It should be stressed, though, that no life has been found beyond Earth, and that “possible” is a long way from “likely”.

F Studying extremophiles is far from easy. Many cannot yet be grown in laboratories, so researchers must study them in place or infer their activity from chemical traces. Collecting samples from deep rock or the sea floor is expensive and technically demanding, and there is a constant risk of contamination: a sample may be contaminated by microbes from the surface or from the equipment itself, leading to false conclusions. The hypothetical research team led by Dr Ines Moreau, for example, spent almost a year developing sterile drilling procedures before collecting a single sample.

G Despite these challenges, the study of extremophiles has already changed how scientists think about life. The question is no longer simply where life can exist, but how far it can adapt. Each new discovery pushes back the boundary of what was thought possible – a reminder that assumptions about nature, however reasonable they seem, may turn out to be far too narrow.