PUBLISHED: 16:12, Sat, Sep 19, 2020 | UPDATED: 16:28, Sat, Sep 19, 2020
Our planet is so far the only world known to contain all the ingredients required for life as we know it. These are liquid water, energy sources, and an array of elements and molecules. However, the recent discovery of bio-signatures in the atmosphere of Venus is a timely reminder of how a selection of these ingredients exists elsewhere in the solar system too. Space agency NASA has now listed the most promising planets for hosting alien life.
Earth’s nearest neighbour Mars is the most obvious candidate for hosting life as we know it, as it is the one most similar to ours.
Mars has a 24.5-hour day, ice caps at its poles, and numerous surface features sculpted by water during the planet's early history.
But arguably most significant of all was both the discovery of a lake beneath the southern polar ice cap and bio-signature of methane in the Martian atmosphere.
However, the specific source for the methane on Mars has yet to be confirmed and may simply be abiotic (not derived from living organisms) in origin.
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NASA has now listed the planets in the solar system most likely to host alien life (Image: Getty)
NASA news: Our planet is the so-far the only world known to contain all the ingredients required for life as we know it (Image: Express)
Experts estimate alien life may have once gained a foothold on Mars.
This is due to evidence Mars once had a much more hospitable environment.
But Mars has an extremely thin and dry atmosphere made up almost entirely of carbon dioxide.
This provides negligible protection from brutal solar and cosmic radiation.
But on the other hand, Mars has managed to retain reserves of water beneath its surface, meaning it is not impossible alien life may still linger underground.
NASA news: Space agency NASA has now listed the most promising planets for hosting alien life (Image: Express)
Jupiter’s moon Europa was discovered by Galileo Galilei in 1610.
Europa is only a larger than Earth's moon and orbits Jupiter at an average distance of 43,495 miles (670,000km) every there and a half days.
The Moon is continually squeezed and stretched by the competing gravitational fields of Jupiter and its other moons, in a process called tidal flexing.
Europa is likely geologically-active Europa because the strong tidal flexing heats its rocky, metallic interior, keeping its mantle molten.
Europa’s surface is a vast expanse of water ice, beneath which many believe is a layer of