As stated in my previous post NASA’s Cassini probe has shown that Saturn’s moon Enceladus not only has an thin atmosphere, but that volcanoes of water are erupting from its surface into space. Even more remarkable has been its discovery, that these volcanoes contain the raw chemicals which are the building blocks for life.
Image from NASA
The question which really fascinates me is – What sort of life could have evolved on Enceladus ?
Before we answer this it is worth thinking about the Earth,which is the only place in the Universe where we know 100% for definite life has evolved !
What stages did life go through while evolving on Earth ?
The Earth formed around 4.6 billion years ago. It is generally accepted that life originated in the sea and later moved onto land. Some rough timescales of the evolution of life on Earth are given below.
- 3.7 billion years ago simple cells
- 1.0 billion years ago multicellular life
- 600 million years ago simple animals
- 200 million years ago mammals
- 60 million years ago the primates (monkeys and apes)
- 20 million years ago the great apes
- 2.5 million years ago the genus Homo (human predecessors)
- 200 thousand years ago anatomically modern humans.
As you can see, although life evolved on Earth fairly rapidly for most of its existence the Earth had only very simple life forms.
What sort of life could exist on Enceladus ?
I think that given that
- the age of Enceladus (which is similar to the age of the Earth)
- all the key ingredients are there: namely water, the chemical builiding blocks for life and an internal energy source
it is highly likely that life has evolved there.
One possibility is that the most advanced form of life is akin to single celled creatures found on Earth, which for most of the Earth’s history was the most advanced form of life.
However, a more exciting possibility is that much more sophisticated life form have evolved in the dark underground oceans. Given the length of time over which evolution could have worked, complex life forms could exist, perhaps preying on simpler life forms. There could be very strange creatures indeed!
Image provided by Sanjay Acharya
Hopefully within the not too distant future we will be able to visit this strange little world and find out more. I will talk more in my next post about possible missions to Enceladus.
Explaining Science 
Hi Steve,
In your original blog you omitted any mention of Europa. Are you planning to consider it in a future item? Unlike the ‘atmosphere’ ejected by Enceladus, we’ve yet to obtain a sample of Europan chemistry, but we can reasonably infer that most of those ingredients are common in large amounts for both bodies. After all, Europa is several AU closer to the Sun, and with a surface accordingly warmer; it’s also rather further from its parent and so its surface & crust would suffer less tidal disruption. (I’m not convinced that volcanic & earthquake activity is always a help to emerging life – though I suppose it helps to weed out some of the less-resilient organisms).
Regards, David Renshaw.
LikeLike
Hi David,
Thanks for your interesting comment. An article on Europa is certainly on my list of topics for future blog posts
Steve
LikeLike
[…] However this does not mean that we expect to see fish swimming in these underground oceans! What is more likely is that, given water, an underground heat source and the raw chemicals, something more akin to single celled creatures and bacteria have evolved on Enceladus. Why I think this is case, I shall say in my next post. […]
LikeLike
Hi Steve, great blog, I like the images interspersed and as a non-scientist the information is accessible and fascinating. I look forward to your next post.
When I signed in I realised I had started a blog a while ago with word press so I’ll find time to add to it i the near future and send you the link, warm wishes, Ruth
LikeLike