Life on other planets
Short answer: Almost certainly.
Longer answer: It is certain that life can arise in the universe. Just look in the mirror. Shortly after the Big Bang, the universe consisted almost entirely of hydrogen and helium atoms, and there was no life. Now there is. Even though we don't know exactly how life originated on Earth, we at least know that it did.
The universe is extremely vast, both in space and time. It is therefore very unlikely that a process that can take place in the universe only happens once. That statistical argument alone makes it very likely that life must have emerged in many other places in the universe.
It is now clear that at least half of all stars are surrounded by one or more planets, and that the organic building blocks of life are abundantly available in interstellar matter. This suggests that the formation of life was not such an unlikely process. Moreover, life on Earth emerged very early in geological history, which also suggests that this was not a 'difficult' or unlikely process.
Astronomers and (asto-)biologists therefore assume that the Earth is not the only 'living planet' in the universe. However, exactly how rare extraterrestrial life is is unknown. To date, traces of alien organisms have never been found on other planets (or moons) in our own solar system.
Future research into the composition of the atmospheres of exoplanets may reveal whether biological activity occurs on the surfaces of those planets. And of course it is in principle conceivable that today or tomorrow we will receive a radio message from an alien civilization, or that an alien spaceship will land in Times Square. It should be noted that, according to evolutionary biologists, it is extremely unlikely that the evolution of life on another planet would necessarily lead to the development of intelligent, technological civilizations.
So for the time being there is no evidence for the existence of extraterrestrial life, but the chance that life has emerged on just one small planet in the vast universe is considered negligible by almost everyone.
Life on Mars:
Mars is a lot like Earth, but its atmosphere is much thinner, the average temperature is much lower, and the planet has no significant magnetic field. This means that the conditions on Mars are very hostile to almost every conceivable life form: there is little or no (liquid) water, and harmful radiation from space reaches the surface unhindered.
However, research on Mars by unmanned space probes in orbit around the planet and by landers and carts on the surface has shown that the planet must have had a much more pleasant climate a few billion years ago, shortly after its formation. The atmosphere then had a much higher density, and due to the greenhouse effect of that atmosphere the average temperature was above the freezing point of water. Seas and oceans almost certainly existed on Mars in that distant past.
If the newborn red planet showed many similarities with the newborn Earth at the time, it cannot be ruled out that life also arose on Mars. Traces of these Martian bacteria might still be found in carefully selected and studied Martian soil samples.
However, the chance seems quite small that any Martian life has survived the major climate change on the planet. The cause of that climate change, in which Mars lost most of its atmosphere and water, is still not well understood, although the planet's small size probably played a decisive role.
Optimists still think that microorganisms might lie close to the surface of Mars. Future Mars research, including through the European-Russian Mars Express project, may be able to provide answers to this question.
And here an docu about we think how alien live look like Alien planet(58 min.) Youtube
