Enceladus: A habitable ice world?

Updated Friday, 27th November 2020
Is it possible that Enceladus, one of the moons of Saturn, could potentially host life? Grace Richards, a PhD student at The Open University, explores...

The Earth is teeming with life and yet we are only one planet, orbiting one star, in a galaxy of over 250 billion stars. Looking even wider into space, we are part of a universe that is a host to at least 200 billion galaxies, each with their respective billions of solar systems. The size of even our galaxy, the Milky Way, leads to questions about whether or not we are the only life forms in the Universe. Although our nearest neighbouring solar system is around 4.5 light years away, looking to the astronomical bodies such as planets, moons, and even asteroids which orbit our Sun can give us valuable information about how life managed to develop on Earth. The variety of life found on Earth has always staggered me; acid-eating microbes, parasitic fungi which infects ants’ brains, and glow-in-the-dark deep sea worms seem alien even on our own planet. If terrestrial life is so variable and bizarre, what would life beyond the Earth look like?

Since the discovery of large, geyser-like plumes at its southern hemisphere, which eject icy material thousands of kilometres into space, this little moon has been thrust centre stage into the search for life in our Solar System.I am a first-year astrobiology PhD student at The Open University and the focus of my research is to investigate the habitability of Enceladus, one of the moons of Saturn. At 504km in diameter, Enceladus is roughly the size of France. Since the discovery of large, geyser-like plumes at its southern hemisphere, which eject icy material thousands of kilometres into space, this little moon has been thrust centre stage into the search for life in our Solar System. These plumes originate from a deep subsurface ocean which is believed to be composed of salty water. In the porous core of Enceladus, hydrothermal activity is suspected to be taking place. This is similar to hydrothermal vent systems on Earth which are able to support thriving biological communities and may have been where life originated. On Earth, life exists where there are organic compounds, liquid water, and an energy source, and Enceladus meets all three of these requirements. Looking at extreme environments such as these allows us to investigate theories into the origin of life and whether or not life elsewhere is possible.

Ideally, we’d like to know more about what is in the ocean. However, it is currently impossible to drill several kilometres through ice and limitations on planetary protection mean that it is unlikely that any future missions will be able to directly sample the ocean. A compromise on this is to sample the plumes and the surface. The plumes play a key role in distributing icy grains globally over the satellite and as they originate directly from the ocean, looking at the surface gives us a better idea of what is happening beneath the ice. That’s where I come in! Although I am in the very early stages of my PhD, my main aim is to develop an instrument to serve as the prototype for future space missions to Enceladus. This will enable us to extract and analyse the icy surface, searching for molecules which provide valuable information about Enceladus’ habitability.

Enceladus close up

Analysing the surface also gives us further information about space weathering processes and the formation history of the satellite. The composition of the ice is altered by the deposition of material ejected by the plumes, micrometeoroid impacts and bombardment of radiation from Saturn’s magnetosphere. As Enceladus orbits Saturn, it also sweeps up material from the E-ring through which it travels. The E-ring is Saturn’s second outermost ring and is composed of microscopic icy grains, which are fed into the ring via the Enceladus plumes. Understanding how these processes affect the surface of the satellite is vital to developing instrumentation best suited to analysing surface components.

The main challenge I expect to encounter is building the actual instrument. Not studying chemistry past GCSE level has led to gaps in my knowledge which I am currently improving by working through various basic chemistry courses. Although I am a physicist by training and have a little experience with electronics, developing a system with the necessary capabilities to accurately analyse ices will be demanding. I am confident that through the relevant training and the help of the team at The Open University I will be able to gain the necessary skills to achieve this.

However daunting this project may be, I am excited about the prospect that my research will be able to have a direct influence on future space exploration missions. Although we do not expect to find evidence of any glow-in-the-dark sea worms in the depths of Enceladus’ ocean, I am incredibly lucky to be able to contribute to research which allows us to investigate the potential for life in the outer Solar System.

This article was originally published on the AstrobiologyOU website. 

This article is part of the Astrobiology Collection on OpenLearn. This collection of free articles, interactives, videos and courses provides insights into research that investigates the possibilities of life beyond the Earth and the ethical and governance implications of this.



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