Extraterrestrail Life Landed on Earth Many Years Ago

Such is the hypothesis two Australian resear­chers, Paul Davies and Charles Lineweaver, recently offered. They have published their observations in the Astrobiology magazine.

Alas, small green creatures possessing phenomenal tech­nologies are out of the ques­tion. According to the two sci­entists, the aliens are likely to be primitive microbes that appeared on Earth some 4 billion years ago.

As is known, our planet at the time was being bombard­ed by meteors and giant

asteroids which probably carried some living organisms to Earth, where they now modestly live among humans. The researchers think that the bombarding of Earth could result in a series of “stop-go” experiments, in the course of which life appeared to be later destroyed by a hail of meteors and asteroids.

Some life forms, however, could have survived the bombardment and may now lurk deep below the Earth’s surface, in the oceanic depths, in the atmosphere or in contaminated lakes. They have even colonized Mars, Davies says. Moreover, the extraterrestrials may live under our very nose being so alien to us that we are simply unable to discover them.

"We could try to find them with the help of modern technologies, we just ha­ven't bothered to do that," Paul Davies says. "Alien microbes are likely to be missed or discarded in even the most general microbial analysis."

The aliens may also have no properties that would reveal them to be living organisms. They may just lie motionless at some place waiting for conditions necessary to spring to life. "For all these reasons we could be sur­rounded by living, dormant or dead alien microbes with­out being aware of it," Davies concludes.

He says the relatively recent discovery of tiny microbes that look like bacteria but genetically differ greatly from all the known species may serve as an indirect evi­dence of the existence of extraterrestrial microbes.

"Microbial world has many hidden surprises, one of which may be alien life," Davies explains. "Our con­clusion is that alien micro­bes could exist on earth today and have remained undetected by our best efforts."

UNIT 4

WORRIES ABOUT WORLD’S ECOLOGY

Text 1

The Vanishing Ozone Layer

The depletion of the ozone layer is a problem that has very similar implications from the viewpoint of ecological democracy than the issue of global warming: everybody will suffer from a problem to which some people – the world's rich minority – contribute much more than the others. Most of the emissions that are damaging the ozone layer are still produced by West Europe and North America, which only have about one eighth of the world's population.

Ozone, the three-atomic molecule of oxygen, has two very different roles. In the lower atmosphere (troposphere) it is a greenhouse gas that contributes to the global warming. It is also poisonous to people and harmful for plants. However, the thin layer of ozone in the upper atmosphere (stratosphere) filters the most damaging forms of the Sun's ultraviolet radiation and prevents them from reaching the ground level. Without this protection we would be exposed to much more intensive and dangerous X-radiation. This would increase the rate of skin cancers and cataracts and damage many food crops. Serious loss of ozone could also reduce fish catches by killing fish larvae that are vulnerable to strong ultraviolet radiation.

In the early 1970's scientist became worried about the possibility that nitrous oxides from fertilizers, supersonic aeroplanes and space shuttle flights might destroy stratospheric ozone. Somewhat later it was understood that also the so called freons or CFC compounds (chloro-fluoro-carbons) were harmful for the ozone layer. CFCs were first used in fridges and air conditioning systems and later as cleaning solvents, aerosol propellants and to puff up polystyrene foam for hamburger cartons and for other purposes. Their world production rose from 2200 tons in 1940 to 491 700 tons in 1970, and it was still growing by 20 per cent per year when it was discovered that the CFCs were both strong greenhouse gases and efficient ozone-depleting substances.

The issue was taken seriously only five years after the British scientists had discovered a vast "ozone hole" over the Antarctic in 1982. The delay was caused by an American satellite, whose computer had been programmed to ignore the impossible results. Thus the satellite did not see the ozone hole and could not confirm the results reported by the British ground stations. It took five years before the confusion was sorted out. At that time the Antarctic ozone hole had grown to cover an area of 14 million square kilometres. Under this area almost all stratospheric ozone vanished during the spring months.

After the existence of the Antarctic ozone hole had been confirmed, the governments started to move with a record speed. The Montreal Protocol on Substances that Deplete the Ozone Layer was negotiated and signed in 1987. In the Montreal Protocol the signatory governments agreed to cut their CFC emissions. During the coming years further meetings of the parties adopted more ambitious targets and finally agreed to phase-out the CFCs and most other ozone-depleting substances. According to the Environmental Protection Agency of the USA, these treaties are likely to prevent about 137 million cases of skin cancer and about 40 million cataracts before the year 2075, so they certainly were a major victory for the humans and for the environment.

However, we still have the problem of nitrous oxide from nitrogen fertilizers and from the burning of fossil fuels. According to the UN's Intergovernmental Panel on Climate Change the nitrous oxide concentrations in the atmosphere are likely to rise by 45 per cent by the year 2100. The Australian research agency CSIRO says that the ozone levels in the mid-latitudes are likely to recover a little because of the elimination of the CFC production. However, they should start falling again around the year 2040 because of the build-up of nitrous oxide into the atmosphere. CSIRO predicts that the ozone layers above the mid-latitudes should be about 9 per cent lower at the end of the century, and they could keep on falling with an accelerating speed.

The new threat to the ozone layer could be even more serious than the CFCs, unless the problem will be prevented in advance. The ozone depletion caused by chlorine and bromine compounds mostly occurs in mid­winter, when there is less sunlight in the northern latitudes and when the people are usually well covered because of low temperatures. But most of the ozone loss caused by the nitrous oxide takes place in mid-summer when the ultraviolet radiation is the most intense and when people generally wear much less clothing. The damage caused by nitrous oxide is also likely to concentrate on the mid-latitudes where the majority of the world's population lives, and not on the unpopulated polar regions.

It is likely that nitrous oxide will become a major topic in international environmental negotiations in the near future. The most important ways to tackle the problem are to promote organic farming, in which chemical fertilizers are not used, or to develop nitrogen fertilizers that do not cause significant nitrous oxide emissions.

Some types of chemical nitrogen fertilizers that are in use now, especially anhydrous ammonia and aqua ammonia, produce approximately one hundred times more nitrous oxide than the most benign alternatives like sodium nitrate and nitrogen solutions.

Text 2

Озоновые дыры – следствие глобального потепления

Ученые обнаружили жесткую связь между потеплением и озоновыми ды­рами, которые регулярно появляются, главным образом, над полюсами нашей планеты. В журнале Science появилась статья, в которой группа исследователей из НАСА, возглавляемых профессором Азадехом Табазадехом, рассказывает о кольцевых облаках, которые рождаются в стра­тосфере и уничтожают озон.

Об этих облаках известно давно, однако только сейчас выяснилось, что они зарождаются при помощи впервые обнаруженных в стратосфере полос холодного воздуха. По мере того как поверхность Земли нагрева­ется из-за парникового эффекта, стратосфера становится все холоднее. Мало того что вся стратосфера замораживается, так еще выясняется, что в ней начинают появляться кольцевые полосы более холодного воздуха. Кольцевые облака, появляющиеся при помощи этих полос, состоят из во­ды и азотной кислоты. А так как состоят они из сравнительно крупных ча­стиц – размером с крупицу дорожной пыли, – то быстро опускаются вниз, попутно высасывая из атмосферы азот и тем самым нанося земной атмо­сфере двойной вред: во-первых, они связывают азот, который в свобод­ном состоянии частично компенсирует вредное воздействие озоновых дыр, а во-вторых, раскалывают молекулы фреонов (газов, запрещенных сейчас международными соглашениями, а прежде широко применяемых в качестве хладагентов), тем самым активизируя молекулы хлора, которые с еще большей жадностью начинают выедать озоновый слой.

По словам Азадеха Табазадеха, чем больше появляется таких обла­ков, тем труднее восстанавливается озоновый слой. Единственное спасе­ние – приостановить глобальное потепление. Если температура в страто­сфере стабилизируется, кольцевые облака станут дефицитом, а так как выпуск фреонов в атмосферу сейчас ограничен, то и озоновый слой со временем придет в норму. Дальнейшее же потепление может сделать си­туацию с озоновыми дырами необратимой.

Text 3

Дата добавления: 2014-11-14; просмотров: 272; Нарушение авторских прав

Мы поможем в написании ваших работ!