Are the planets habitable?

Ever since it was known that the planets were bodies more or less like the earth, people have asked: “Are the living thing on them?” This is a hard question to answer, but by combining the resources of the most of sciences, we can give a rather good answer.

The success achieved in developing of rocket-space technology, beginning with the first artificial satellites and automatic stations to the Moon and other planets greatly influenced the development of all the branches of science and technology. For a very short period of time the flight of space apparatus, the probing of the planets atmospheres, the soft landing of automatic stations on the planets' surfaces have provided so much information never obtained before.

The modern level of the development of space technology has opened the road to the direct experimental solution of the basic problem – whether there is life on planets or not.

First let's consider life of our earth. All living things are absolutely dependent on water. Moreover, this water must not be liquid- ice nor gaseous water vapor, but ordinary liquid water. Nothing grows while it is frozen. And no living thing would survive if the water was boiled out of it. Hence it's necessary that the temperature on a habitable planet part – all the time, and below the boiling point all the time.

Light is necessary too. Practically all the food in the world is produced by green plants. Plants get the energy they require for their growth from sunlight.

There is a good reason to believe that the vast store of oxygen in the air has all been supplied by plant. If there were no plants, there would be no food for eat, no oxygen-containing air to breathe.

If we inquired whether other planets were habitable, we should then try to find out whether their temperature were suitable for life, whether they had water and atmosphere on them, and if so, whether oxygen and carbon were present.

Measurements of planetary heat have shown that on Mercury, which is the nearest planet, there is a great difference between the day and night temperatures which are 350 ºC and – 175 ºC respectively. This planet is evidently inhabitable by any form of life known to science. Temperatures range from 150 to 200 degrees below zero for the remoter planets. Biological experiments carried out by space apparatus completely disprove the existence of highly developed living organisms on thee planets, but they give hope that there are probably microorganisms on them. The Moon, which has been explored both by automatic vehicles and by man, shows no trace of atmosphere or water. Physical conditions are entirely unsuitable for the existence of living protein on the moon and therefore it also is a dead world.

Now only Venus and Mars are left for consideration. Venus has a large quantity of carbon dioxide (97%) in her atmosphere, but too little oxygen and water vapor. The maximum surface temperature is 300 º C, which is unsuitable environment for the existence of life.

Mars has a thin atmosphere, so we can see the surface clearly. The planet has seasons like our own, and the heat measurements indicates that in the tropics the temperature rises to about 127 º C above freezing point and falls below freezing (-70 º C) every night.

Spectroscopic observations show that there is about 95%of carbon dioxide in its atmosphere. They indicate, too, that there is very little oxygen and water vapors (0.1% and about 1% respectively) on Mars. Whether animal life has ever existed on Mars and whether it has been able to survive has not yet been established. The majority of scientists who, with the help of space apparatus, have explored the planet's physical conditions came to the conclusion that life is possible on Mars.

The data obtained recently on Moon, Venus and Mars considerably widen our conceptions of these heavenly bodies – ideas that have been formed throughout the history of observations and the development of astronomy. The ultimate result of all this is the progress in studies of nature.

COMMENTARY

ever since - з тих пір як

living things - живі істоти

are left for consideration - залишаються для розгляду

above/below freezing point - вище/нижче точки замерзання

thin atmosphere - розріджена (тонка) атмосфера