The discovery of signs that may indicate the presence of microbial life on Venus has raised a more popular debate on the subject, although they have yet to be confirmed. However, even if life is not confirmed there, there is no problem. Venus is a hostile planet, difficult for life to survive. But there are some friendlier places throughout the solar system, and only one of them is a planet.
Mars(Image: ESO/M. Kornmesser)
Mars is, for sure, the most classic of them all. The planet is humanity's biggest focus for manned missions nowadays. But we need to go to the Moon first, to be able to refuel the rocket, and have fuel left over so the astronauts can come back.
Even though there are no humans there, there are dozens of robots, both on the surface and in orbit around the planet. Many of them have as one of their main missions the detection of evidence of life.
The planet is very similar to Earth, and in the past it may have been even more similar . It is believed that Mars may have had oceans and at least microbial life. Although it is more desert-like today, life could still thrive, or at least signs of past life.
Europe(Image: NASA/JPL-Caltech/SETI Institute)
Europa is one of Jupiter's many moons. Discovered in 1610 by Galileo Galilei, it's one of the largest of them - a little smaller than our moon. And it's a pretty promising place too.
An interesting point there, is the existence of tidal forces . As it dances around Jupiter, it is stretched sideways by the strong gravity. This can generate heat for microorganisms.
Also, tidal forces cause its interior to remain very warm, just like on Earth, so there is still geological activity there, and that's a great sign for sustaining life.
Encelado(Image: NASA/JPL/Space Science Institute/Kevin M. Gill)
Sailing a little further we arrive at Saturn. And Enceladus orbits the planet. Covered by a layer of ice, it may look deserted. But don't stop there.
Beneath Encelado's ice lies a gigantic, complex ocean, where a variety of microscopic creatures may live. These possibilities were made even more promising by the discovery of geysers in 2010.
The importance of heated water is for the withdrawal of energy. Hence the importance of geological activity. Hydrothermal vents are also where life arose on Earth, and where they thrive away from sunlight.
TitanPhoto of Titan with a seasonal illumination, taken by Cassini (Image: NASA-JPL/ESA)
Titan is perhaps the most fascinating of Saturn's moons, and we've already talked here about the planet's smell . While it probably has a mixture of rotten and sweet smells (which probably isn't very pleasant), it can be a good home.
With a very dense atmosphere, Titan has all the complexity present on Earth - seasonal changes, complex organic molecules. But it's also very cold on the surface.
By temperature and atmospheric pressure, methane is liquid there (on Earth it's a gas). And there are rivers and methane rain on Titan. For microbial life, there's also heated water inside. All the ingredients for life are there.
With information from Live Science .