HomeEarth10 Lesser Known Factors that Support Life on Earth Charles January 4, 2017 Earth, Listicles, Sky Science doesn’t like to describe things as miracles. However, when you consider the incredible complexity of the combination of events that gave rise to life on Earth, it’s hard not to think of it as such. Although life on Earth has suffered no shortage of mass extinctions, such as those caused by climate change and impact events, it has proven itself overall to be highly adaptive and resilient. That being said, our very existence is a product of all these occurrences, ranging from the fine-tuning of photosynthesis to the stabilising effects of the Moon. While the following factors that support life on Earth don’t necessarily preclude life from developing, they have had such a profound effect on evolution that we’d be pretty much doomed without them. #1. The Moon PixabayFar more than just a lifeless chunk of rock, the Moon has a major effect on life on Earth including its influences on the nocturnal world. What would happen if there were no Moon? There’s a multitude of reasons why our nearest celestial neighbour is so important. For one thing, the Moon has a stabilising effect on Earth’s axial tilt, thus keeping it from varying too much and causing far greater seasonal variation and unhindered climate change. Countless species have also adapted to life with our unusually large moon to the extent that it has profound effects on the nocturnal world. However, perhaps most importantly of all is the likelihood that lunar tides were instrumental in helping early life migrate from the oceans to tidal flats and, eventually, onto the land. Although the Sun also influences ocean tides, it does so with relatively little effect. #2. Volcanic Eruptions PixabayAside from being instruments of destruction, volcanism has also played a vital role in the formation of Earth’s atmosphere. From Tambora to Vesuvius, volcanoes have been associated with destruction and chaos since time immemorial. What few people realise, however, is that life on Earth would have been severely stunted without them. Although credited with various extinction events throughout our planet’s history, outgassing by volcanoes, along with the help of impact events, during the Hadean was instrumental in transforming the atmosphere into what we breathe today. Before outgassing added nitrogen and water vapour to the atmosphere, Earth was instead covered in a blanket of hydrogen left over from its formation. Additionally, volcanism has also helped to shape the world’s landmasses, produce water for the oceans and stabilise core temperatures. #3. Greenhouse Gasses PixabayGreenhouse gasses aren’t all bad. In fact, they’re vital for keeping Earth warm enough for life. Without it, the whole globe would be frozen solid. There’s little doubt that human-influenced global warming is having a profound effect on our environment but, as usual, nature manages to put our efforts to shame. Throughout most of Earth’s history, CO2 levels have been much higher than they are today, reaching as much as 0.7 percent during the Cambrian Period, as opposed to today’s 0.04 percent. As evidenced by global warming, CO2 has a major effect on our climate to the extent that it keeps Earth much warmer than it would otherwise be. Without naturally occurring greenhouse gasses, which are caused largely by volcanism and as a by-product of life itself, Earth’s average surface temperature would plummet to −18°C compared to the comfortable 15°C we enjoy today. #4. Galactic Position PixabayOur solar system is in just the right area of the Milky Way, where there are plenty of heavy elements for forming rocky planets and there aren’t so many other stars getting in the way. Most people realise that Earth is just the right distance from the Sun to support life as we know it. However, just as there’s a stellar habitable zone, there’s also a galactic habitable zone. For a start, the central region of the Milky Way, or any other galaxy for that matter, is extremely inhospitable due to vast amounts of radiation, densely packed star clusters and regular supernova events. On the other hand, areas closer to the edge of the galaxy have lower metallicity, meaning there are fewer heavy elements, such as iron, for the formation of solid planets. The galactic habitable zone is expected to be very large, extending from the edge of the core to about 32,600 light years, with both radii having quite flexible boundaries. #5. Good Jupiter NASAJupiter is often credited as the Solar System’s vacuum cleaner, but it also has a stabilising effect on the inner planets. At a minimum distance of 365-million miles (588-million km), the vast gas giant might not seem very important to us here on Earth. However, owing to their enormous size, planets like Jupiter and Saturn exert gravitational forces strong enough to significantly influence the orbital stability of all the other planets in our solar system. These stabilising effects on Earth’s orbit have a profound effect on stabilising the planet’s climate, thus reducing the risk of there being more devastating extinction events than there already are. Although Jupiter’s role as the solar system’s vacuum cleaner is still not well understood, the planet may also help to keep the inner solar system relatively free of potential impactors like comets. #6. Molten Core PixabayThe auroras, which are visible at either low of high latitudes, are caused by the solar wind interacting with Earth’s vital magnetosphere. Some bizarre things happen in the centre of the Earth. With the weight of thousands of miles of rock pushing down from all directions, the pressure is equivalent to 47,700 elephants sat on your head, and the temperature is 5,400°C. Molten iron comprises the outer section of the core, and it rotates around a solid centre that’s about 70% the diameter of the Moon. This process creates a dynamo effect that in turn generates our magnetic field. Without this critical magnetosphere, life on Earth would perish, and the solar wind would strip away our breathable atmosphere and bathe the surface in lethal radiation. Planets without magnetospheres include Venus and Mars, both of which are deadly environments for life as we know it. #7. Suitable Size NASAMars is a good example of a planet that’s not massive enough to retain a breathable atmosphere for long enough that complex life may evolve. While it’s common knowledge that Earth-like life cannot exist on something as small as an asteroid or as large as a gas giant, the planetary size and mass requirements are rather more rigid than many people realise. Mass is by far the most important planetary characteristic, since it directly translates into surface gravity and, in turn, to atmosphere retention and geological activity. For example, Mars’ low mass, relative to its size, makes it difficult to hold onto a breathable atmosphere and, consequently, prevent water from evaporating instantly. Geological activity also ceases sooner on smaller planets, transforming them into cold, dead worlds, before any kind of complex life has a chance to establish a foothold. #8. Life-Giving Chemistry PixabayAll life on Earth is composed of six fundamental elements: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulphur, as well as trace amounts of various other elements. Many of the factors that support life on Earth are specific to the past and present ecosystems of our planet. In other words, alternative biochemistries, such as those that rely on chemicals other than water or those that use entirely different building blocks, would have a completely different set of requirements. Nonetheless, one universal rule of any form of biochemistry, hypothetical or otherwise, is that it can only come into being due to chemical reactions. No chemical reaction may occur if the right conditions aren’t in place first, and without the right chemical reactions, a planet’s surface will remain completely inert. Here on Earth, we exist only because conditions allowed chemistry to create crucial molecules, such as DNA and RNA. #9. Energy NASAThe discovery of completely independent ecosystems that rely on deep-sea hydrothermal vents for sustenance make the subsurface ocean of Jupiter’s moon Europa one of the most promising places for extraterrestrial life. Most people are aware that all life requires an energy source to exist and, understandably, most of us immediately point to the Sun as the reason for the existence of life. However, while the Sun is certainly crucial to the existence of almost all life on Earth, there are a few important exceptions. Deep-sea hydrothermal vents right here on Earth are home to fully self-contained ecosystems that draw their energy purely from geological activity. There are no plants requiring sunlight for photosynthesis, and the lowest organisms in the food chain rely solely on volcanically produced nutrients to survive in an environment that’s as different from our own as the sub-surface oceans of Jupiter’s moon Europa. #10. Ancient Life Josef reischigCyanobacteria is one of the oldest forms of life on Earth, and it played a key role in oxygenating the Earth’s atmosphere as such that multi-cellular life could evolve. Life has existed on Earth for at least 3.5-billion years, likely first arising during the Archean. However, it wasn’t until around 1.2-billion years later that multi-cellular life evolved during the Proterozoic. Although many of us will remember from school that plants pump oxygen into the atmosphere as a by-product of photosynthesis, it’s actually a tiny microscopic organism we have to thank for making our atmosphere breathable. Some 2.3-billion years ago, the evolution of photosynthesising cyanobacteria spiralled out of control, causing the Great Oxygenation Event. However, while this event spelled the end for many species of anaerobic bacteria, for which oxygen is toxic, it also laid the foundations for complex life to evolve. 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