What could life on another planet be like?

That life on other planets exists is a tempting idea! But how would extraterrestrial life look like? And to what extent does it resemble terrestrial life? For a start we should ask ourselves what affected and still affects life on our planet.

A condition sine qua non for the development of life is a friendly environment.This would for instance mean that other planets also revolve around a sun. On these planets life could exist, whereas life on a star would be highly improbable.

A further problem or condition is the distance between the planet and its sun, because the latter one strongly affects the climate. Obviously the exact terrestrial temperatures are not absolutely necessary for life to develop, since different forms of life exist in proximity of volcanoes on Earth. However too huge a variation would impede the emergence and development of life.

A different solar spectrum would also have an impact on life. Consequently one could imagine that extraterrestrial forms have a different type of skin or eyes, more appropriate to the conditions imposed by the light.

A further problem concerns the planet's features. Without atmosphere, a protective layer, life would be exposed to dangerous radiations and other negative external influences. It is hardly probable that an organism could bear this. Thus the structure of the atmosphere plays an important role. Terrestrial life-forms need oxygen to survive. But it would be quite conceivable that there is none, or not enough on an other planets. Terrestrial conditions could be absent and the existence of life nevertheless possible. There are probably forms of life that can cope with the outermost atmospheric conditions. But then, their physical appearance might be tightly related to the composition of their surrounding atmosphere.

The next determining factor for the development of life is the planet's gravity. On a planet with a strong gravity one could expect to find mainly creeping or swimming (if a liquid element exists) life-forms. On the contrary, upright going or flying organisms are here very improbable, since the strength needed for this is too huge. Meanwhile, on a planet with a smaller gravity flying forms of life are conceivable.

Of course the structure and composition of the planet is of great importance. A planet only made of gas may not promote development of life. On a planet with many liquid elements, swimming forms of life are probably predominant, while creeping or flying organisms would rather exist on a dry planet. The presence of water, at the origin of life on earth, is not indispensable. But it could be a very helpful element for life on other planets,too. Eventually the planet must provide the elements, e.g. a sort of nutriment, that organisms need to produce energy and to survive.

One element is often missing in the discussions about life in the universe: evolution. It is conceivable that extraterrestrial life exists, but at a bacterial stage. Or, on the contrary, it may well be far more advanced than terrestrial life. In both cases, a 'meeting' or even communication between human beings and Aliens is hardly possible. To get to know the structure of an extraterrestrial society would surely be very interesting. Perhaps they live in a free society, like us.Perhaps they live in a totally different kind of society, completely alien to us.

There are many speculations concerning life in the universe. As a matter of fact, there have to be lots of coincidences and the presence of many elements necessary to evolution to create a life-form similar to the terrestrial one. Supposing there were other beings in the universe and that they would meet humans, communication is almost certainly impossible, because of enormous differences between our respective anatomies and thoughts. No one knows what extraterrestrial organisms look like. But one can make assumptions, even if every supposition may be entirely contradicted once. Finally it will remain a surprise until the actual discovery of extraterrestrial life.