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Space settlements could ensure a future for life beyond Earth in the event of natural or human-made catastrophes. (credit: Blue Origin)

Why you should care about life beyond Earth

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Life on Earth has faced five mass extinctions over the past 500 million years. Ensuring the long-term survival of life as we know it will require humanity learning how to migrate the myriad species of Earth off their home planet, because, as its long history shows, this planet can sometimes be a very dangerous place for life to be. If we are truly concerned for the well-being of generations long to come, then we owe to them our commitment to establishing permanent, sustainable habitats in outer space. The longer we choose to not act, the longer we test our fate.

The longer we choose to not act, the longer we test our fate.

Mass extinctions have had various natural causes. Some, such as the Permian extinction of 250 million years ago, resulted from internal forces. This extinction, also known as the “Great Dying”, was most likely caused by a series of massive volcanic eruptions that wiped out 90 percent of all species.[1] Spilling over four million cubic kilometers of lava across what is now Siberia, these eruptions wreaked havoc on a global scale, ejecting vast amounts of sulfur and carbon dioxide into the atmosphere, poisoning both the air and the oceans.[2]

External forces have caused mass extinctions as well. Most infamously, the end-Cretaceous extinction came about 66 million years ago when asteroid ten kilometers in diameter impacted Earth near what is now Mexico’s Yucatan Peninsula.[3] Striking the planet with the force of 100 million megatons of TNT[4] (equivalent to two million detonations of the Tsar Bomba, the largest nuclear weapon ever tested)[5] , the asteroid generated massive earthquakes and tsunamis in the region of the impact and led to devastating consequences for life across the globe: ejecta from the impact ignited massive wildfires as far away as Australia, heat-induced chemical reactions caused acid rain to fall for months, and dust and aerosols shut down photosynthesis in plants by blocking the light from the Sun. This effect on plant life broke down the food chain and spelled the end not only for most herbivores, but also for the carnivores that hunted them.[6] Ultimately, the asteroid impact would eliminate 75 percent of terrestrial and marine species.[7]

Luckily, we have taken steps to reduce the risk of an asteroid impact sending us the way of the dinosaur. According to data from the Johns Hopkins University Applied Physics Laboratory, of the 1,000 near-Earth objects that are large enough to have a global impact effect, only four have a mass large enough to cause mass extinctions, and neither of these is currently on track to pose an impact threat.[8] Additionally, efforts like NASA’s recently successful DART mission highlight our ability to potentially alter the path of near-Earth objects that may pose a threat in the future (assuming that we recognize those threats in time to react and they are not so large that deflection is a futile effort).

Asteroids, however, are not the only extraterrestrial threat to life as we know it. The Ordovician-Silurian extinction was likely caused by an abrupt decline in global temperatures and mass glaciation about 440 million years ago. Experts are still searching for evidence to determine the trigger for this deadly era of global cooling, but some theorize that it was caused by a massive gamma-ray burst from a relatively nearby supernova. Such an event could have depleted Earth’s ozone layer by as much as 40 percent, allowing more ultraviolet radiation from the sun to pass through the atmosphere, poisoning all organic matter in the direct path of the sun’s full force. It is also likely that a gamma-ray burst would have created nitrogen dioxide (smog) in the atmosphere, blocking out sunlight and abruptly triggering an ice age.[9] As with planet-killing asteroids, however, ozone-shredding gamma ray bursts are also extremely unlikely. Although a gamma-ray burst could pose a threat to life from as far away as 10,000 light-years[10] , Earth would need to be in the direct path of a supernova’s gamma ray burst and the planet is in a part of the galaxy where supernovae are rare.[11]

External threats to life on Earth appear to be extremely low probability events, but as history shows, they are possible. Plus, despite the vast knowledge of the cosmos we have gained over the past century, there could be other destructive phenomena that we simply haven’t discovered yet. At most, we know that we have five billion years until a swelling, dying Sun swallows up our home planet.

If our path to sustainability relies on continued environmental degradation and child labor, we are not really changing our relationship with the planet, or ourselves.

Setting aside threats from beyond, however, it would be quite naive of us to assume that Earth will not again pass through the types of great geological transformation that led to mass extinctions in the past. The “supervolcano” currently at rest below Yellowstone National Park in Wyoming is one potential source of geological catastrophe that should give pause, especially to those living in the western half of the United States and Canada. According to the US Geological Service (USGS), Yellowstone experienced three caldera-forming eruptions between 2.1 million and 640,000 years ago. Were it to erupt today, the supervolcano would bury surrounding states in at least one meter of ash and disrupt the global climate for years or even decades. One can imagine the social, economic, and political instability that such as event would cause. Fortunately, the USGS estimates that there is only a 0.00014 percent chance of Yellowstone erupting in the next few thousand years.[12]

Alongside the super-deadly volcanoes, asteroids, and gamma-ray bursts that have threatened life in the past, an additional threat to life as we know it has come upon the scene. That threat, of course, is human beings. Humans have a history of leaving behind a trail of destruction. Even in pre-historic times, when we were simple nomads tracking game out of Africa and across the globe, where humans have arrived, lots of other species, especially megafauna, have been put at risk.[13]

Now, in our hyper-industrialized times, we have entered what some scientists refer to as the Anthropocene. In the Anthropocene epoch, humanity has altered Earth at a level that can be measured geologically. Land clearance to make room for industrial farming and urban development has led to biodiversity loss, soil degradation, and other hazards. The various pollutants associated with industrialization and modern agriculture threaten our air and water quality. And the carbon emissions created by the burning of fossil fuels are beginning to warm the planet and disrupt climate patterns in a way that even skeptics of climate change can no longer deny. All of these factors are increasingly pushing life on Earth towards a sixth mass extinction. [14]

Although humanity is taking efforts to reduce its carbon emissions and mitigate the effects of climate change, even if we were to achieve carbon neutrality tomorrow, we still do not know the full effects of the damage we have already wrought on planet Earth, our only home. Additionally, barring serious discussion about changing our consumption patterns, our growth-centric transition to clean energy shows little sign of being more sustainable in the long run than our current dependence on fossil fuels. For example, Western consumers can pat themselves on the back for shrinking their carbon footprint by driving around in electric vehicles, but 80 percent of the global supply of cobalt, a key component in electric vehicle batteries, is sourced from the Democratic Republic of the Congo, where at least 25,000 children work in the cobalt mines and there are few resources available to protect laborers or the environment.[15] If our path to sustainability relies on continued environmental degradation and child labor, we are not really changing our relationship with the planet, or ourselves.

Along with the relatively new hazards to life created by humanity’s impact on the environment, no discussion on mass extinction would be complete without a mention of the perpetual threat of nuclear war. Despite reductions in overall numbers, the United States and Russia each still maintain over 5,000 nuclear warheads total in their respective inventories, and China is starting to ramp up its supply.[16] Luckily, the world has not faced a real close call since the 1962 Cuban Missile Crisis (as far as we know), but rising tensions between nuclear powers have caused arms reduction efforts to fall out of favor in recent years. These tensions have been exacerbated further by Russia’s invasion of Ukraine and Vladimir Putin’s threats to use nuclear force. Adding a new twist to the threat of nuclear winter, recent advances in artificial intelligence (AI) bring to mind the risk of a “Skynet” moment when the machines become self-aware and decide that the most efficient and elegant way to solve all of humanity’s problems is to simply destroy all of humanity.

This all paints a rather bleak picture for life’s prospects. Even if Earth were to stay free from natural catastrophe until the end of time, humans and their devices still have the potential to ruin it all. But, although humans may be the greatest current threat to life on Earth, we are also capable of life’s salvation. For better or worse, humans are the only species capable of preserving life as we know it (although it is comforting to hope that Douglas Adams was not just writing fiction when it comes to the intellect of dolphins and mice.)[17] And, despite our best efforts to find evidence in our universe to the contrary, life on Earth is it. Therefore, we should be doing all we can to maintain the habitability of our planet for present and future generations.

But, if in our current focus on addressing climate change our ultimate goal is to preserve the environment for future generations, then we also owe it to those future generations to begin preparing today for potential tomorrows where Earth is rendered largely inhabitable due to natural calamity or human error. Given all of these threats, life itself needs an insurance policy: for life to eventually inhabit the vast space that lies beyond Earth.

Humans, of course, have been living in space continuously since the International Space Station (ISS) went live in the early 2000s, but, with all due respect to the achievements of the ISS, a small research post in low Earth orbit is hardly a proverbial second basket to preserve life’s eggs. Not only are the inhabitants of the ISS completely reliant on Earth for supplies, we know after two decades of research that the microgravity environment is unequivocally terrible for the physical health of organisms that evolved to survive and thrive in a 1g environment.

Space migration is not an either-or proposition. We do not need to choose between either life on Earth, or life beyond it.

Truly sustaining life beyond Earth will require the eventual construction of space habitats that are large enough to permanently house self-sufficient populations, while providing both artificial gravity and protection from radiation. Many are enthusiastic about one day living on the Moon or Mars, but what little research has been done to learn the effects of partial gravity on the body is not promising.[18,19] , Even the months-long trip to Mars will require artificial gravity for the crews to be healthy enough to accomplish anything of value upon their arrival.[20]

Constructing large-scale, permanent space habitats is obviously a long-term project. But it is by no means fanciful. Since the 1970s, when Gerard O’Neill spelled out his vision for a “High Frontier” populated by humans and other species living comfortably in massive, free-floating space habitats, the world has known that such habitats are technically feasible.[21] In O’Neill’s time, the largest obstacle was the cost. Now, however, the globe is awash in wealth (whether that wealth is distributed fairly or efficiently is another matter.) Total wealth in the United States alone has risen from approximately $25 trillion in 1980 to well over $100 trillion today,[22] and total global wealth now stands at about $500 trillion.[23] Investing just one percent of humanity’s current wealth into a project to preserve life as we know it would be a massive down payment on our future, and would provide enough capital to fund the ISS 30 times over.[24]

Earth has served life well, and we should do our best to keep our home safe and secure. But the planet’s long history shows that is has gone through tumultuous periods of being far less hospitable for its many inhabitants—and that was even before humans showed up. Taking the early steps now, we could achieve a not-too-distant future where millions of humans and numerous other species are surviving, thriving, and multiplying in space. A future where heavy mining and industry have moved off-planet and most of Earth’s territories and waters have been allowed to return to their natural, pristine state. We have had the science for decades, and now we have the means to finance such a venture. All that is missing now is the will.

Some argue that space is a distraction, that we should be focusing our attention and resources on problems here on Earth instead of indulging the fantasies of messianic billionaires. But space migration is not an either-or proposition. We do not need to choose between either life on Earth, or life beyond it: life first migrated from the oceans hundreds of millions of years ago, but the oceans remain home to countless species. In fact, the same innovations that will enable life to thrive beyond this planet can also be applied to improve conditions for life that remains on it. As one example, the same technologies that will be applied to grow food in space could also be used to grow food anywhere on Earth.

Perhaps thousands of years from now our space-faring descendants will return to Earth from some distant civilization in another solar system to visit the home world of their visionary ancestors who first ventured into space. What they would find is anybody’s guess. They could encounter a planet that still teems with life, including their distant Earthling cousins. Or they could find a hot (or cold) and desolate wasteland, long ago done in by some random asteroid, supernova, or other cosmic event. No matter what the future holds, however, the greatest chance we have to preserve the long-term prospects for life on this planet is by developing the means to thrive off of it. And that is why you should care about life beyond Earth.


  1. Jennifer Chu. “Timeline of a mass extinction.” MIT News, 18 Nov.2011.
  2. Jennifer Chu. “An extinction without warning.” MIT News, 18 Sep. 2018.
  3. Alfio Alessandro Chiarenza et al. “Asteroid impact, not volcanism, caused the end-Cretaceous dinosaur extinction.” PNAS, vol. 117, no. 29, 2020, pp. 17084-17093.
  4. Lunar and Planetary Institute. Chicxulub Impact Event, 2020. Accessed 14 Oct. 2023.
  5. Wikipedia, “Tsar Bomba.” Accessed 14 Oct. 2023.
  6. Lunar and Planetary Institute. Chicxulub Impact Event, 2020. Accessed 14 Oct. 2023.
  7. Ibid.
  8. Planetary Defense Interagency Working Group. “National Preparedness Strategy & Action Plan for Near-Earth Object Hazards and Planetary Defense”. National Science & Technology Council, Apr. 2023.
  9. A.L. Melott et al. “Did a gamma-ray burst initiate the late Ordovician mass extinction?” International Journal of Astrobiology, vol. 3, no. 1, 2004, pp. 55-61.
  10. Ibid.
  11. John P. Millis. “Should you be worried about gamma-ray bursts?” ThoughtCo, 10 Jan. 2020.
  12. United States Geological Survey. “Yellowstone”. Accessed 14 Oct. 2023.
  13. Wikipedia. “Holocene Extinction”. Accessed 14 October 2023.
  14. Katie Pavid. “What is the Anthropocene and why does it matter?” Natural History Museum.
  15. Michael Posner. “To meet global demand, companies must reform mining practices in the Congo.” Forbes, 9 Feb. 2023.
  16. Federation of American Scientists. “Status of World Nuclear Forces”. 31 March 2023. Accessed 14 Oct. 2023.
  17. Douglas Adams. The Ultimate Hitchhiker’s Guide to the Galaxy. Del Rey Books, 2002.
  18. Marie Mortreux and Megan E. Rosa-Caldwell. “Approaching gravity as a continuum using the rat partial weight-bearing model.” Life, vol. 10, no. 10, 2020, pp. 235.
  19. Peter R. Cavanaugh et al. “A novel lunar bed rest analogue.” Aviation, Space, and Environmental Medicine, vol. 84, no. 11, 2013, pp. 1191-95.
  20. Gilles R. Clément, Angelia P. Bukley, and William H. Paloski. “Artificial gravity as a countermeasure for mitigating physiological deconditioning during long-duration space missions.” Frontiers in Systems Neuroscience, vol. 9, 2015, pp. 92.
  21. Gerard K. O’Neill. The High Frontier. Space Studies Institute Press, 2019.
  22. Anthony Shorrocks, James Davies, and Rodrigo Lluberas. G“lobal wealth 2019: The year in review”. Credit Suisse Research Institute, Oct. 2019.
  23. Jonathan Woetzel et al. “The rise and rise of the global balance sheet”. McKinsey Global Institute, Nov. 2021.
  24. Claude Lafleur. “Costs of US piloted programs.” The Space Review, 8 Mar. 2010.

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