The scientific reason why there is no Planet B

by Arwen Nicholson & Raphaëlle aywood

Editor’s note: It’s fascinating to me that many of the more scientifically-minded people advancing the idea of interplanetary colonization (in response to climate change and ecosystem collapse) are the least realistic about the science of it. I think this is partly a function of techno-optimism, the irrational faith in the ability of technological innovation to overcome any problem. Relatedly, it’s also a failure to appreciate the complexity of biological life. And lastly, it’s a function of an objectified consciousness, which fails to appreciate the relationships between things–in this case, the relationship between human beings and the planet we have co-evolved with.

This is an excerpt. You can read the complete essay here.


… Given all our technological advances, it’s tempting to believe we are approaching an age of interplanetary colonisation. But can we really leave Earth and all our worries behind? No. All these stories are missing what makes a planet habitable to us. What Earth-like means in astronomy textbooks and what it means to someone considering their survival prospects on a distant world are two vastly different things. We don’t just need a planet roughly the same size and temperature as Earth; we need a planet that spent billions of years evolving with us. We depend completely on the billions of other living organisms that make up Earth’s biosphere. Without them, we cannot survive. Astronomical observations and Earth’s geological record are clear: the only planet that can support us is the one we evolved with. There is no plan B. There is no planet B. …

Deep down, we know this from instinct: we are happiest when immersed in our natural environment. … Our bodies instinctively know what we need: the thriving and unique biosphere that we have co-evolved with, that exists only here, on our home planet. …

From an astronomical perspective, Mars is Earth’s twin; and yet, it would take vast resources, time and effort to transform it into a world that wouldn’t be capable of providing even the bare minimum of what we have on Earth. …

Let’s imagine that some futuristic form of technology exists, ready to whisk us away to this new paradise. Keen to explore our new home, we eagerly board our rocket …

As it turns out, we have landed on a perfect twin of the Archean Earth, the aeon during which life first emerged on our home world. This new planet is certainly habitable: lifeforms are floating around the green, iron-rich oceans, breathing out methane that is giving the sky that unsettling hazy, orange colour. This planet sure is habitable – just not to us. It has a thriving biosphere with plenty of life, but not life like ours. In fact, we would have been unable to survive on Earth for around 90 per cent of its history; the oxygen-rich atmosphere that we depend on is a recent feature of our planet. …

It is only within this aeon that our atmosphere became one that we can actually breathe. This aeon has also been characterised by multiple mass extinction events that wiped out as much as 90 per cent of all species over short periods of time. The factors that brought on such devastation are thought to be a combination of large asteroid impacts, and volcanic, chemical and climate changes occurring on Earth at the time. From the point of view of our planet, the changes leading to these mass extinctions are relatively minor. However, for lifeforms at the time, such changes shattered their world and very often led to their complete extinction. …

This time also experienced global glaciation events known as snowball Earths, where ice covered the globe from poles to equator for millions of years at a time. Earth has spent more of its time fully frozen than the length of time that we humans have existed. …

[W]e would have been incapable of living on our planet for most of its existence. Anatomically modern humans emerged less than 400,000 years ago; we have been around for less than 0.01 per cent of the Earth’s story. The only reason we find Earth habitable now is because of the vast and diverse biosphere that has for hundreds of millions of years evolved with and shaped our planet into the home we know today. Our continued survival depends on the continuation of Earth’s present state without any nasty bumps along the way. We are complex lifeforms with complex needs. We are entirely dependent on other organisms for all our food and the very air we breathe. The collapse of Earth’s ecosystems is the collapse of our life-support systems. Replicating everything Earth offers us on another planet, on timescales of a few human lifespans, is simply impossible. …

It’s also worth considering that many of the attitudes towards space colonisation are worryingly close to the same exploitative attitudes that have led us to the climate crisis we now face. …

Earth is the home we know and love not because it is Earth-sized and temperate. No, we call this planet our home thanks to its billion-year-old relationship with life. Just as people are shaped not only by their genetics, but by their culture and relationships with others, planets are shaped by the living organisms that emerge and thrive on them. Over time, Earth has been dramatically transformed by life into a world where we, humans, can prosper. The relationship works both ways: while life shapes its planet, the planet shapes its life. Present-day Earth is our life-support system, and we cannot live without it. …

finding alien life does not mean finding another planet that we can move to. Just as life on Earth has evolved with our planet over billions of years, forming a deep, unique relationship that makes the world we see today, any alien life on a distant planet will have a similarly deep and unique bond with its own planet. …

Living on a warming Earth presents many challenges. But these pale in comparison with the challenges of converting Mars, or any other planet, into a viable alternative. …


This is an excerpt. You can read the complete essay here.

Published by John Halstead

John Halstead is the author of *Another End of the World is Possible*, in which he explores what it would really mean for our relationship with the natural world if we were to admit that we are doomed. John is a native of the southern Laurentian bioregion and lives in Northwest Indiana, near Chicago. He is a co-founder of 350 Indiana-Calumet, which worked to organize resistance to the fossil fuel industry in the Region. John was the principal facilitator of “A Pagan Community Statement on the Environment.” He strives to live up to the challenge posed by the Statement through his writing and activism. John has written for numerous online platforms, including Patheos, Huffington Post, PrayWithYourFeet.org, and Gods & Radicals. He is Editor-at-Large of HumanisticPaganism.com. John also facilitates climate grief support groups climate grief support groups affiliated with the Good Grief Network.

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