Exoplanets, alien atmospheres and life, Jim…but not as we know it!

Written by David Robertson, who attended a lecture by Dr Giovanni Tinetti (UCL Physics & Astronomy) at the Cheltenham Science Festival, entitled ‘Exoplanet explorers’.

1992, was the year it hit me! As I entered the brave new world of primary education, I remember being startled with the knowledge that we lived on a ball of rock, travelling some 67,000 miles per hour around a massive burning ball of fire. Naturally, this was a pretty terrifying turn of events!

As the shock subsided, and my terror turned to awe, I was told that the Earth was one of a small group of planets orbiting our local star.

There was more.

After hearing of Goldilocks’ run-in with the three bears, a great intellectual leap was made in which this theoretical framework was used to explain the presence of liquid water, thought to be a major prerequisite for the existence of life, on earth.

In contrast, the other known planets in our solar system, which are closer or further than us from the sun, were considered to be either too hot or too cold to provide the conditions necessary to sustain liquid water and, potentially, alien life.

We knew that there were nine planets.

Well, that was until Pluto entered administration, was deprived of its ‘full’ planet status (it is now categorised as a dwarf planet) and subsequently relegated to the lower echelons of the planetary leagues.

We knew that there were eight planets.

We knew of only one, the Earth, in which liquid water and life was to be found.

Some may say I am paraphrasing, but the previous statements would appear to pretty much sum up most of the more important aspects of our knowledge of planets and the likelihood of finding life beyond Earth during that period.

We had no idea if our solar system was special, could it really be the case that our Sun was the only star in the sky to play host to orbiting planets? If there were no other planets that were capable of sustaining water in its liquid state, did this mean that the probability of finding life beyond our world was pretty grim?

In the intervening 20 years, it is quite incredible how much our knowledge of the universe has improved.

In terms of planets, we have now confirmed the presence of 800 worlds orbiting other stars in our galaxy, with potentially billions more yet to be discovered (eight always seemed a bit on the conservative side), and in terms of the likelihood of life arising on these ‘exoplanets’ (planets that have been discovered outside our solar system), we may have been focusing our attention in entirely the wrong place.

That was the verdict of a distinguished group of exoplanet explorers, who gave a fascinating presentation at this year’s Times Cheltenham Science Festival.

Kicking things off was UCL’s very own astrobiologist and exoplanet expert extraordinaire, Dr Giovanna Tinetti. She provided an overview of the great strides that we have taken in our ability to detect, confirm and categorise extrasolar planets.

This included a nod to NASA’s Kepler mission, which is devoted to the search for habitable planets orbiting at a distance from their star that could allow liquid water, and potentially life, to exist.

As recently as April this year, the Kepler team confirmed the existence of three such planets orbiting in that ‘Goldilocks zone’.

The second exoplanet explorer was Dr David Acreman (University of Exeter’s Astrophysics Group). This part of the discussion outlined the way in which the methodological tools used to construct climate models here on Earth, could be applied to the exoplanet data we have, in order to reveal the atmospheric composition of these alien worlds.

The final speaker was distinguished physicist and astrobiologist Professor Paul Davies. He outlined the thought-provoking idea that there could be life here on earth, but not as we know it. What if life began on earth more than once? What if we are currently sharing our planet with, as yet undiscovered, microbial life forms whose biochemistry differs from that which we know?

This controversial notion of a ‘shadow biosphere’ developing here on earth is an interesting approach to answering the question of whether we are alone in the universe. The logic being that if life arose independently, on more than one occasion on Earth, then the probability of it arising elsewhere in the cosmos increases.

There is no doubt that we are still at the beginning of our exploration and understanding of planets beyond our home star system.

However, our knowledge of these alien worlds will accelerate dramatically over the coming decade and beyond, as more and more exoplanets are confirmed and our ability to satisfy that driving curiosity to know what these planets are like improves.

So, are there other Earth-like planets out there in the vastness of space? Has life developed ‘out there’? The research being conducted now and in the future will bring us closer to answering these fundamental questions.

So sit back and enjoy the ride as we all become exoplanet explorers.

David Robertson is a PhD student at the UCL Institute of Cognitive Neuroscience. His research focuses on attention, distraction and human information processing.