The Four Most Promising Planets for Alien Life in the Solar System

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The biosphere of Earth contains all the elements we know are necessary for life. These are generally: liquid water, at least one energy source, and a breakdown of biologically useful elements and molecules.
However, the discovery of possible phosphine in Venus’s clouds reminds us that several of these elements are found in the Solar System.
So what other places are suitable for alien life?


Mars is one of the Earth-like planets in the Solar System. With 24.5 hours a day, Mars has vast glaciers and contrasting seasons. It is also covered with ground shapes carved by water throughout the planet’s history. The discovery of the lake under the southern glacier and methane in the Martian atmosphere makes the planet a very interesting candidate for life.

Methane is important because it is produced by biological processes, but the actual source of methane on Mars is not yet known. Today Mars is almost all carbon dioxide filled, dry, and has a fairly thin atmosphere. So it means limited protection against sunlight and cosmic radiation. If Mars managed to contain some water reserves on its surface, it is not impossible to still have life.


Europa, along with the other three major moons of Jupiter, was discovered by Galileo Galilei in 1610. A little smaller than the Moon and 670,000 km from Jupiter, Europa completes its tour around Jupiter in 3.5 days. Europa is believed to be geologically active like Earth because the strong tides heat the rocky and metallic interior and leave it partially molten.
Europa’s surface is covered with water ice. Many scientists think that this frozen surface is a layer of an ocean 100 km deep. We could probably find hydrothermal vents and volcanoes under this ocean. Such elements mean a very rich and diverse ecosystem in the world.


Like Europa, Enceladus is an ice-covered satellite with an ocean of groundwater. Enceladus, orbiting Saturn, caught the attention of scientists as the huge geysers near the satellite’s south pole was surprisingly discovered and a habitable world.
Water escaping from large cracks in the surface is spraying into space. These geysers are clear evidence of liquid water stored underground. Not only water but also organic molecules and silicate particles were found in these geysers. This is strong evidence of the existence of hydrothermal vents that provide the chemistry necessary for living and established energy sources.


Titan, Saturn’s largest and the only moon in the Solar System with a rich atmosphere, a satellite covered with a thick orange haze of mixed organic molecules, is complemented by its surface filled with seasonal rains, dry periods, and dunes. Much of the atmosphere is made up of nitrogen, the chemical element found in proteins in all known life forms. Radar observations discovered the possible presence of lakes of liquid methane and ethane and volcano-like cryovolcanoes that spew water instead of lava. This gives the impression that Titan has underground water reservoirs such as Enceladus and Europa. Titan, which is quite far from the Sun, has a temperature of -180 degrees. However, the abundance of chemicals found in Titan has spurred speculation about life forms that could live there.