Exploration of the Solar system and search for life

The exploration of the Solar system is an important part of the search for life in space. Automated space exploration instruments have visited most of the planets in the Solar system and some of their satellites, some comets and asteroids. So far, according to the scientists, the most probable places for life to have existed in the past (in the form of microorganisms) are Mars, Europa (one of Jupiter’s moons), and Enceladus (one of Saturn’s moons). All of these have had (or still have) liquid water on their surface or close to it. Another of Saturn’s moons - Titan, is also interesting, because it seems that it has lakes of liquid methane, and Titan itself, with its geologic activity and atmospheric composition is very similar to the Earth in its earliest ages.

Another way to search for life in space, in which a lot of amateur astronomers take part, are the experiments aiming to register signals from a technologically advanced alien civilization. Since the 1960s, the SETI (Search for ExtraTerrestrial Intelligence) program analyzes electromagnetic signals coming from space (mainly in radio and visible light) with the hope to detect a signal from an extraterrestrial civilization. Of course, SETI is not hoping to detect a signal in any human language, but is searching for structures in the signals that can not occur in any natural way. So far, they have had no success.

We people have also sent greetings into space with the hope that they might be received by an alien civilization. Among them are messages in binary code, transmitted by radio telescopes on Earth, but also messages, written in different codes that are traveling on board of space crafts. The Voyager 1 and 23 space crafts (https://voyager.jpl. nasa.gov/mission/status/) carry on board albums with pictures and sounds that illustrate the diversity of life and human cultures on Earth. Among them is a Bulgarian folklore song from the Rhodope region. Both these space crafts have already left the Solar system and continue their voyage in space.