Is other life sustainable in the solar system?

We can say with a reasonable degree of certainty that there is no other intelligent civilisation in our solar system.

We can say with a reasonable degree of certainty that there is no other intelligent civilisation in our solar system. There are no little green men on Mars waiting for the opportunity to seize our planet. But that doesn’t mean there is no other life at all.
In this article I’m going to go through the various bodies of the solar system and the theories that exist about the possibility of life there.
Close to the Sun and lacking an atmosphere, there is no real possibility that Mercury plays host to even microbial life. 
Until the 1970s, planet Venus was considered to be a swamp planet, possibly hosting a vibrant jungle teeming with a rich diversity of life just beneath its thick atmosphere.  
It was surely a prime candidate for life elsewhere in the Universe. Unfortunately, we took a closer look at it and it is a truly hostile planet. Venus has a poisonous atmosphere, soaring temperatures and such pressure that you’d be crushed, choked and cooked within seconds of opening the door of a spaceship.
Despite this, a theory has been put forward that microbes could live high in its atmosphere. How we would go about detecting them is an issue however.
The Moon
No atmosphere and weak gravity. Like Mercury it is hostile to life.
Martians have long been a staple of science fiction and the red planet is considered a primary candidate to host life. It is widely held that Mars previously had liquid water on its surface and that life may well have once existed there. It is possible that it still does. The Curiosity Rover is currently on Mars and will hopefully find evidence that life either existed or still does exist there.
This is a dwarf planet located in the asteroid belt. Frost has previously been detected on its surface, as has water vapour in the atmosphere. Both of these indicate there may be water on the planet that could potentially host life.
This gas giant has no solid surface and is ravaged by storms that can last for centuries. Like Venus it couldn’t be more hostile to life as we know it if it tried.
That said, also like Venus, theories have been put forward suggesting life could exist in microbial form in its atmosphere.
The Moons of Jupiter
While Jupiter is not considered accommodating to life its moons are a different story. Three of the four largest moons – Europa, Ganymede and Callisto are believed to have sub-surface oceans. This, combined with the tidal effect the gravitational pull of Jupiter would have, makes them perhaps the most viable candidates for life.  
Europa is particularly exciting as its surface is ice-covered. One study suggested that a viable eco-system could exist deep within its oceans. Again the issue is getting down to them.
Another gas giant, perhaps the most beautiful planet in the Solar System but totally hostile to all forms of life.
The Moons of Saturn
Saturn has over sixty moons but only two are considered likely prospects to hold life. Titan, the planets largest moon, is the only moon in the solar system with a significant atmosphere with liquid hydrocarbons on its surface. It also rains, the only place outside Earth we know that this happens.
Scientists have speculated that microbial creatures there may be producing methane, but nothing has been proven.
Enceladus is smaller and wasn’t considered at all special until 2005 when a geyser was detected firing ice and gas out of the moon. This indicates there may be water beneath the surface, again raising the potential for life.
Uranus and Neptune
Both gas giants, there is little prospect of them or their moons hosting life.
So there you have it. If there is life in our system then it will be very hard to find and most likely microbial.  I for one would love to see Europa examined in more detail in my lifetime.
It is a personal dream of mine to be kicking around the day they finally confirm that we’re not alone.
What do you think? Have your say in the comments section below.
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