Major discovery in outer space gives massive boost to hope of finding alien life

The chances of finding life on other planets has just been given a huge boost as many more exo-planets may harbour liquid water than previously thought.

Water is vital for life to occur, and so scientists searching for organic matter focus on regions and planets where it could feasibly form in a liquid state. 

Previously, this has been in the circumstellar habitable zone (CHZ), the area around stars warm enough to maintain liquid water – and more specifically, the CHZ around M-dwarf stars. These common stars are cooler than the Sun, but make up around 70% of the stars in the Milky Way, and most known exo-planets orbit M-dwarfs.

However, new research has shown exo-planets beyond the CHZ have two main mechanisms of liquifying water, meaning life may still be able to flourish.

‘As Earthlings, we are lucky at the moment because we have just the right amount of greenhouse gases in our atmosphere to make liquid water stable on the surface,’ said lead author Lujendra Ojha. 

‘However, if Earth were to lose its greenhouse gases, the average global surface temperature would be approximately -18 degrees Celsius, and most surface liquid water would completely freeze. A few billion years ago, this actually happened on our planet and surface liquid water completely froze. 

‘However, this doesn’t mean that water was completely solid everywhere. For example, heat from radioactivity deep in the Earth can warm water enough to keep it liquid. Even today, we see this happening in places like Antarctica and the Canadian Arctic, where despite the frigid temperature, there are large underground lakes of liquid water, sustained by the heat generated from radioactivity.

‘There is even some evidence to suggest that this might be even happening currently in the south pole of Mars.’

In addition to heat generated by radioactivity, Dr Ohja and his team highlighted the gravitational effects of nearby planets and moons in churning water on other bodies.

‘Some of the moons you find in the solar system – for example, Europa or Enceladus – have substantial underground liquid water, even though their surfaces are completely frozen,’ said Dr Ojha, an assistant professor at Rutgers University. ‘This is because their interior is continually churned by the gravitational effects of the large planets they orbit, such as Saturn and Jupiter.

‘This is similar to the effect of our Moon on tides, but much stronger. This makes the moons of Jupiter and Saturn prime candidates for finding life in our solar system, and many future missions have been planned to explore these bodies.’

Both Nasa and the European Space Agency have missions bound for Jupiter’s icy moons, Clipper and Juice respectively, but neither will arrive until 2030.

In addition to these solar system neighbours however, the findings suggest a 100-fold increase in the chances of finding water – and possibly life – in our galaxy.

‘We modelled the feasibility of generating and sustaining liquid water on exoplanets orbiting M-dwarfs by only considering the heat generated by the planet,’ said Dr Ojha. ‘We found that when one considers the possibility of liquid water generated by radioactivity, it is likely that a high percentage of these exoplanets can have sufficient heat to sustain liquid water – many more than we had thought.

‘Before we started to consider this sub-surface water, it was estimated that around one rocky planet every 100 stars would have liquid water. The new model shows that if the conditions are right, this could approach one planet per star. So we are a hundred times more likely to find liquid water than we thought. 

‘There are around 100 billion stars in the Milky Way Galaxy. That represents really good odds for the origin of life elsewhere in the universe.’

The study is published in the journal Nature Communications.

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