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Реферат: Is There Really Life On Mars Essay

Название: Is There Really Life On Mars Essay
Раздел: Топики по английскому языку
Тип: реферат Добавлен 18:51:26 29 октября 2010 Похожие работы
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Is There Really Life On Mars? Essay, Research Paper

If there was a wet climate on Mars in the past, as the channels imply, perhaps there was lifeformas well; could life, in some form, remain in the martian soil today? The time has come for America to commit itself to a bold new venture in space: the human exploration and settlement of Mars. We’re ready. (Zubrin) Robert Zubrin, a reporter for USA Today, made that bold statement in April of this year. His article goes on to defend the human adventure to Mars — why we should do it, how to do it. But one question remains in every mind who has studied the stars on a clear winter night or wondered what if? after watching a particularly frightening science fiction movie. That singular question, answered in part by the Pathfinder Mission, has been . . . what or who will we find there?

In August of 1996, NASA scientists revealed a rock ejected from Mars by meteoric impact which showed strong evidence of life on Mars in the distant past. If scientists can qualify this most amazing discovery, it would undoubtedly demonstrate that the origin of life is not unique to the Earth. If the origin of life is not unique to Earth, it means humans exist in a universe that is filled with life. If it is filled with life, how difficult of a cognitive leap is it to assume that the universe is then probably filled with other intelligence as well. From the point of view of humanity learning its true place in the universe, this would be the most important scientific enlightenment since Copernicus.

The canals charted through a telescope by astronomer Percival Lowell almost a century ago at his observatory in Flagstaff, Arizona, turned out to be just an imaginative figment when Mariner 9 mapped much of Mars in 1971. (Lowell had become a leading exponent of the idea that the canals were constructed by living creatures to irrigate their crops.) Five years after Mariner 9, when America’s two Viking spacecraft settled onto Mars’ surface, conditions were found to be so hostile that life was essentially ruled out. Chemical tests showed the soil on Mars is so rich in potent chemicals called peroxides that organic matter – which is needed for life – is quickly destroyed. (Cooke) In actuality, Venus may be closer to being Earth s twin in terms of size, but Mars has more specific characteristics in common with Earth than does any other planet. The Martian year lasts 23 Earth months, but the Martian day is only 41 minutes longer than an earth day and its inclination of 24 degrees to its rotational axis is very close to Earth s 23.4 degrees. As a result, Mars has four seasons that parallel those experienced on Earth. The Martian

summer is, relatively speaking, warmer than its winter. Mars ids the only other planet in the solar system other than Earth that has polar ice caps, and these can be seen to expand and recede seasonally, just like the ice caps on Earth. (Yenne)

Mars is a great deal smaller and less dense than Earth. Because of this. Mars has less gravity and a much thinner atmosphere than Earth. It is also colder than Earth, with temperatures in its polar regions rarely rising above 200 degrees Farenheit. The midsummer temperature near the Martian equator can, however, reach a comfortable (by human standards) 80 degrees Farenheit, closer to an Earthly temperature range than can be found anywhere else in the solar system. (Yenne) Because of that one Martian rock found on the ice in Antarctica, and because science’s understanding of biology, especially microbiology, expands so dramatically each year, the thought of life on Mars (in the past and the future) has once again become a very real possibility. The rock – a meteorite creatively named AH84001 consists of minerals called carbonates, organic molecules called PAHs (polycyclic aromatic hydrocarbons) and small germ-like bodies that could be fossilized microbes, says David McKay, of NASA. The carbonites especially hint that

water once was present.

It was McKay’s team that was responsible for uncovering the life-like evidence from the meteorite and stunned the world of science with the announcement the summer before last. We never claimed to have found life,” McKay said. But he insists, there were lines of evidence supporting the possibility that life did occur on Mars. He has since added, we have a lot of new data [from the meteorite], and we think we’ve got additional supporting evidence – but no smoking gun at this time. (Cooke)The information gained from the meteorite suggests that even though Mars’ surface is fundamentally hostile to life because of the peroxides, and intense ultra-violet radiation from the sun, life beneath the soil may still be possible. The meteorite found in Antarctica seems to have come from deep beneath Mars’ surface. At the same time that these extra-terrestrial studies have been focusing on Mars, new studies of life in extreme environments on Earth are showing that life survives, and may even have originated, underground. Ken Nealson, the microbiologist in charge of the NASA team examining exobiology (the search for life on other planets) said in an interview for Newsday that all of this results in , a very exciting time. New findings, Nealson said, indicate that not only is life on Earth very uniform in its chemistry, it also evolved in a flash. Back 3.8 billion years ago there was functioning life on this planet. At the same time, Mars was a wet and warm planet. It s estimated that Earth formed 4.6 billion years ago. (Cooke) If the conditions on both planets were actually very similar at the beginning, researchers say, then there seems to be no obvious reason why the same chemical and physical conditions didn’t lead to life on both Earth and Mars.

It’s also now very clear, Nealson said, that micro-organisms can survive for millions of years, and they can be brought back to life after being stored in soils and in fossilized tree pitch, or amber. (Cooke) These are scientific speculations that weren t even considered at the time when the Viking spacecraft tested Mars’ soil in 1976. Many scientists, Nealson one of them, say that this validates science s enthusiasm for re-investigation of Mars in order to seek out the remnants of ancient life, regardless of the form it may have taken. According to NASA biologist Gerald Soffen, the key is H-2-O. Even though life on Earth is described chemically as being carbon-based, it’s really water-based. So on Mars what we’re concerned about is liquid water. (Cooke) The Pathfinder spacecraft wasn’t equipped to find life, and certainly not to prospect for water. But what it can and was able to do is check on rock chemistry, seeking rocks that were created or altered by water. The subject of water is important, Soffen said, and we believe there is a great deal of water in the soil, frozen in the form of permafrost. (Cooke) Nealson, whose expertise concerns organisms called extremophiles – microbes that thrive in ultra-hot water, in deep cold, or in very salty environments – said the recent finding show how very tenacious life can be. Spores that are at least 20 million years old can be brought back to life, he said, and that knowledge tells you something about the tenacity of life, which we obviously didn’t know when the Viking spacecraft sought signs of life on Mars in 1976. These insights, the limits of survival for microbes, have been totally redefined since Viking. (Cooke) Perhaps the answer to life on Mars lies closer to the Martian poles where there is more water, or the question might be restated simply to whether or not life might have existed at one time on Mars. In the long-gone days of rivers on the surface of Mars, did some civilization or even just a species of moss flourish along their banks? Even if Earth s paleontologists or archaeologists one day discover fossils or ruins amid the rust-red sands of Mars . . . what does it mean to humans and planet Earth? There are three clear reasons to pursue the study of whether or not life did exist or can exist on Mars. The first is a very simple reason for the continuation of focused study . . . knowledge.

The second reason is equally straightforward . . .challenge. Nations, like people, thrive on challenge and decay without it. The space program itself needs challenge. Consider: Between 1961 and 1973, under the impetus of the moon race, NASA produced a hundred times the rate of technological innovation it has shown since, for an average budget in real dollars only about 20% more than today. Why?

Because it had a goal that made its reach exceed its grasp. You don’t need to develop anything new if you are not doing anything new. Far from being a waste of money, forcing NASA to take on the challenge of Mars is the key to giving the nation a real technological return for its space dollar. (Zubrin)

The third reason is probably debatable to many critics but it is (simply) . . . the future. Mars is not just a scientific curiosity; it is a world with a surface area equal to all the continents of Earth combined, possessing all the elements that are needed to support not only life, but also technological civilization. Mars is our New World. Someday millions of people will live there. What language will they speak? What values and traditions will they cherish, to spread from there as humanity continues to move out into the solar system and beyond? When they look back on our time, will any of our other actions compare in value to what we do today to bring their society into being? (Zubrin) We have the opportunity to be the founders and shapers of a new and dynamic branch of the human family. This is undeniably a privilege to be disdained lightly.

Carr, Michael Possibilities for Life on Mars (U.S.

Geological Survey, 1997)

Cole, K.C., Studies of Meteorite Give Boost to Theory of

Fossil Life From Mars

(Los Angeles Times, 3/14/97)

Cooke, Robert The Mars Landing / The Search for Mars Life

(Newsday, 1997)

Yenne, Bill The Atlas of the Solar System: Mars (Exeter

Books, 1987)

Zubrin, Robert Time for The Leap to Mars (USA TODAY,


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