To harbour life, even in the simplest of forms, there are three main requirements that must be fulfilled. These are:
- Liquid water
- A source of energy for the living organism to use
- Biogenic chemical elements such as carbon, phosphorous and sulphur, as well as hydrogen and oxygen (provided by water)
But, Pluto’s surface is so cold, there is no way there could be life, right?
Agreed. It would be near impossible for there to be life existing on the surface of this small dwarf planet. Pluto is so far from the sun, that barely any thermal energy will reach it’s surface, meaning the average temperature on the dwarf planet’s surface is -230°C (or 33 K). This already rules out the first and second requirements for life. At -230°C there certainly will not be any liquid water, nor will there be a sufficient energy source for the living organisms.
So, if there is no life on Pluto’s surface, where else could we find it?
Beneath the surface, of course! It is likely that Pluto’s inner surface is partly an ocean surrounding a rocky core. This is shown below in figure 2.
How is there a liquid ocean beneath the surface if Pluto is -230°C?
This is all thanks to the rocky core within the dwarf planet, which contains uranium, thorium and potassium-40. These elements are radioactive and slowly decay within the core of the dwarf planet. This decay will break up water molecules in a process known as radiolysis, which ultimately provides the energy to ensure that the water can be maintained as a liquid. The ocean itself is thought to contain a high concentration of ammonia, which allows the ocean to be liquid at a temperature lower than the freezing temperature of water. Ammonia could also act as a source of nitrogen, which is an important building block in both amino acids, which make up proteins, and within DNA.
NASA’s New Horizons mission did a fly by of Pluto and the Kuiper belt, with the data being sent back to earth over the course of a year. From this data it does appear that liquid water has been detected on Pluto.
Perhaps there is life flourishing in the distant and cold seas of Pluto. This may once have seemed a completely farfetched and radical idea, however, by analysing all the given evidence, life on Pluto (even if it’s just a few microbes) cannot be ruled out!
References:
https://solarsystem.nasa.gov/planets/pluto/faq
https://phys.org/news/2016-12-life-pluto-ocean.html
https://www.universetoday.com/14315/is-there-life-on-pluto/
https://nasa.tumblr.com/post/162981388079/that-time-we-flew-past-pluto