admin Asteroid strikes, supernova explosions and other disasters could wipe out humanity. Either way, a catastrophic event in 1 billion years could deprive the planet of oxygen and wipe out life.
Life is inherently resilient. According to some scientists, the first living organisms on Earth appeared 4 billion years ago. At that time, our planet was still being hit by giant space rocks.But life continues to exist. And throughout Earth’s history, Earth has experienced all kinds of disasters. Apocalypses ranging from supernova explosions and asteroid strikes to massive volcanic eruptions and sudden climate change have killed countless life forms. And sometimes, these mass extinctions even wipe out most species on Earth.
Yet, life always comes back. New species appear. The cycle repeats itself.
So if you want to completely destroy life, what should you do? Well, it turns out that even though humanity is surprisingly fragile, sterilizing the entire planet isn’t easy. However, below are some possible apocalyptic events that could permanently destroy all life on Earth – and the last one is probably inevitable.
Asteroid impact apocalypse
When a city-sized asteroid struck the Gulf of Mexico 66 million years ago, it was game over for the dinosaurs, as well as most other species on Earth at the time. And while our ancestors hadn’t yet evolved, the impact was perhaps the single most important event in human history. Without that asteroid strike, dinosaurs might have continued to rule the Earth, leaving us mammals still cowering in the shadows.
However, humans are not always the winning side in such random events. A future asteroid could easily wipe out every single person on Earth. Fortunately, this is unlikely to happen anytime soon. Based on geological data from space impacts, Earth is hit by a large asteroid about every 100 million years, according to NASA. However, smaller asteroid impacts happen all the time. There is even evidence that some people may have been killed by small meteorite impacts over the past few thousand years.
But what are the chances that our planet will one day be hit by an asteroid large enough to wipe out all life on Earth? Simulations published in the journal Nature in 2017 showed that it would take a truly massive space rock to achieve such a feat. Destroying all life on Earth would require an impact that could literally boil the oceans. And only asteroids like Pallas and Vesta – the largest in the solar system – are big enough for that.There is evidence that the newborn Earth was attacked by a large planet called Theia. But today, collisions of such large objects are extremely unlikely.
Death by deoxygenation
To get a more likely idea of an Earth-changing catastrophe, we need to look to the distant past.
Nearly 2.5 billion years ago, a period called the Great Oxidation Event provided us with the breathable atmosphere we all depend on today. The outbreak of cyanobacteria, sometimes called blue-green algae, filled our atmosphere with oxygen, creating a world where multicellular life forms could colonize and where creatures like humans could eventually breathe.
However, one of Earth’s largest mass extinctions, an event that occurred 450 million years ago and is called the Late Ordovician mass extinction, probably happened because the opposite happened.The planet experienced a sudden drop in oxygen levels that lasted several million years.
What could have caused such an extreme event? During the Ordovician period, the continents formed a confusing mass called Gondwana. Most living things on Earth still lived in the oceans, but plants began to appear on land. Then, at the end of the Ordovician, radical climate change caused the supercontinent to be covered in glaciers.The cooling of the climate alone was enough to trigger the extinction of species.
But then the second extinction pulse increased as oxygen levels decreased. Scientists are seeing evidence of this change in seafloor samples collected around the world. Some researchers believe that glaciers are responsible for fundamentally changing ocean layers, which are characterized by unique temperatures and specific concentrations of elements such as oxygen. However, the exact cause of the drop in oxygen is still controversial.
Whatever the cause, it is estimated that more than 80% of life on Earth disappeared during the Late Ordovician mass extinction.
This may have happened before, but could a deoxidation event happen again? In a stark comparison to today, scientists say in a recent Nature Communications study that climate change is already reducing oxygen levels in our oceans and potentially killing marine species.
Gamma-ray burst extinction
Even if a sudden spate of global cooling sparked the Late Ordovician mass extinction, what set that in motion in the first place? Over the years, numerous astronomers have suggested the culprit might have been a gamma-ray burst (GRB).
GRBs are mysterious events that seem to be the most violent and energetic explosions in the cosmos, and astronomers suspect they’re tied to extreme supernovae. However (and thankfully), we haven’t yet seen a burst close enough to us to fully understand what’s going on. So far, GRBs have only been spotted in other galaxies.
But if one did happen in the Milky Way, as has likely happened in the past, it could cause a mass extinction on Earth. A GRB pointed in our direction might last just 10 seconds or so, but it could still destroy at least half Earth’s ozone in that short period of time. As humans have learned in recent decades, even a relatively small amount of ozone depletion is enough to chip away at our planet’s natural sunscreen, causing serious problems. Wiping out the ozone on a large enough scale could wreak havoc on food chains, killing off huge numbers of species.
A GRB would wipe out the lifeforms that live in the upper levels of the ocean, which currently contribute significant amounts of oxygen to our atmosphere. And, it turns out, gamma rays also break apart atmospheric oxygen and nitrogen. These gasses get converted into nitrogen dioxide, which is more commonly known as the smog that blocks out the Sun above heavily polluted cities. Having this smog blanketing the entire Earth would block out sunshine and kickstart a global ice age.
End of the Sun
Each of the above devastating scenarios, while terrible for life, are only a fraction as terrible as the ultimate fate of the future Earth. Regardless of whether gamma rays explode or not, in about a billion years most living things on Earth will die from lack of oxygen. This is shown by another study published in March in the journal Nature Geoscience.
Scientists suspect that our oxygen-rich atmosphere is not a permanent part of the planet. Instead, in about a billion years, solar activity will cause oxygen levels in the atmosphere to fall to levels before the major oxidation event.To determine this, the authors combined climate models and biogeochemistry models to simulate what will happen to the atmosphere as the Sun ages and puts out more energy.
They found that, eventually, Earth reaches a point where atmospheric carbon dioxide breaks down. At that point, oxygen-producing plants and organisms that rely on photosynthesis will die out. Our planet won’t have enough lifeforms to sustain the oxygen-rich atmosphere humans and other animals require.
The precise timing of when that starts and how long it takes — the deoxygenation process could take as few as 10,000 years — depends on a broad range of factors.Ultimately, however, the authors argue that this catastrophe is inevitable for the planet.
Fortunately, humanity still has a billion years to make other plans.
