Is there any extraterrestrial life that has evolved?

Is there any extraterrestrial life?

For our ancestors heaven was the home of gods, today we look for life on other planets. There seems to be a collective longing for man not to be alone in the vast expanses of the cosmos.

The first primitive forms of life arose on earth around 3.9 billion years ago. Until then, the earth was still exposed to a violent bombardment of cosmic debris, only then could the surface slowly cool down. Rain fell, the first oceans formed - and according to current knowledge, the first unicellular life forms also emerged almost immediately. Many researchers today draw the conclusion from this that life - at least primitive life - arises with ease if only the right conditions prevail.

Bacteria on Mars and Venus?

In the early days of the solar system, life could therefore have originated not only on Earth, but also on our neighboring planets Mars and Venus. According to current knowledge, there was open water on the surface of both planets billions of years ago. Bacteria might even have survived to this day under the surface in the Martian soil or high in the clouds of Venus.

Viking on Mars

The American space agency NASA made a first attempt to prove life on Mars in 1971 with the two Viking probes. But the interpretation of the results is controversial to this day: While one experiment indicated biological activity, a second found only dead matter. Most researchers therefore interpret the results of the first experiment as the result of non-biological chemical reactions in the Martian soil. The European ExoMars probe, the launch of which is planned for 2013, is to undertake a new attempt to prove life on the red planet.

Life under ice armor

Ice armor of Jupiter's moon Europa

But theoretically there could also be life further away from the sun. Several moons of the planets Jupiter and Saturn have oceans of water many kilometers deep beneath their ice sheets. On earth, too, there are life forms that exist under extreme conditions without sunlight, for example in the vicinity of hydrothermal springs in the deep sea.

The discovery of bacteria on other planets or moons would hardly satisfy people's longing for “partners” in space. Whether the further development to complex or even intelligent forms of life is as inevitable as the emergence of single-celled life is hotly debated among scientists. Because on earth this development was a long time coming: for three billion years our planet was populated by bacteria alone. The emergence of complex life could therefore be a rare event dependent on many coincidences - and then the earth would also be a rare special case and humanity would perhaps be the only intelligent species in the Milky Way.