"Idle speculation" has no place in science, but "speculation" is its very lifeblood, a wel

lknown physicist believes.

The more fundamental and far-reaching a scientific theory is, the more speculative it is likely to be. It is erroneous to believe that science is only concerned with "pure facts", for mere accumulation of facts is a primitive form. of science. A mature science tries to arrange facts in significant patterns to see relationships between previously unrelated aspects 'of the universe.

A theory that does not suggest new ways of looking at the universe is not likely to make an important contribution to the development of science. However it is also important that theories are checked by new experiments and observations.

Dr. Ovenden discusses recent discoveries in biology, chemistry, and 'physics that give clues to the possibility of life in the solar system and other star systems. He discusses conditions on Mars, Venus, Jupiter, and Saturn, and considers whether or not the same conditions may be found on planets of other stars.

Only the planets Venus, Earth, and Mars lie within the temperature zone, about 75,000, 000 miles wide in which life can exist. Venus is covered by a dense layer of clouds which permit no observation of the surface, and the surface temperature of the planet is not known.

Mars is colder than Earth, the average temperature being about minus 40 degrees Fahrenheit, compared with plus 59 degrees Fahrenheit as the average for earth. However near the Mars poles during the summer season, temperatures may rise to as much as 70 degrees Fahrenheit, whereas winter temperatures may fall to minus 130 degrees Fahrenheit.

Because of the extreme difference in the Martian(火星的) seasons, the only life forms expected to exist, without a built-in(内在的，固有的) temperature control such as warm-blooded animals and humans have, are those which would stay inactive most of the year.

Attempts have been made to detect in the spectrum of the dark markings on Mars, the absorption lines due to chlorophyII. So far the test has not succeeded. But the infrared spectrum of the Martian markings has been found to be very similar to the spectrum of earth vegetation when studied at high altitudes.

Life, as we know it, most likely would exist on Mars near its ______.

A．poles

B．equator

C．center

D．canals