The Moon is the Earth’s only natural satellite. It is also the fifth-largest natural satellite in the Solar System and the largest among planetary satellites relative to the size of the planet that it orbits. It formed about 4.51 billion years ago from the debris left over after a giant impact between Earth and a Mars-sized body called Theia (this is known as the Giant Impact Hypothesis and is the most widely accepted explanation of the formation of the Moon). This impact happened not long after the Earth has been formed. But, what if that giant impact never happened? What would the Earth without Moon be like?
How was the Moon evolved? “The giant impact hypothesis” is the prevailing theory supported by the scientific community. Like the other planets, the Earth formed from the leftover cloud of dust and gas orbiting the young sun. The early solar system was a violent place, and a number of bodies were created that never made it to full planetary status. According to the giant impact hypothesis, one of these crashed into Earth not long after the young planet was created. The collision that formed the moon was so hard that the entire Earth seems to have entirely melted in the process.
1. The life probably wouldn’t start on an Earth without Moon – or at least it would be very different
The tides would be only about one-fourth of their current size (the Sun also causes tides with stretching and squeezing the Earth). In some scenarios for the origin of life in the primitive Earth, tidal effects caused by the Moon are important since they allow some environments to be alternatively wet and dry. This can favor chemical processes producing prebiotic molecules.
In other words, by driving the tides, our lunar companion may have jump-started the life on Earth, or at least accelerated its progression.
We could be out of the Goldilocks Zone without the Moon
The giant impact that formed the moon most probably changed the Earth’s path around the sun. With this new object orbiting us, our gravitational pull the Sun exerts was also changed.
Without that impact and the moon, we may not be in the same place in our orbit. Our planet might be out of the habitable zone or Goldilocks Zone Notes 1, meaning either it could be too hot or too cold.
In a much colder planet, liquid water may never have flowed on the surface. And without liquid water to flow, life is nearly impossible to exist. On the flip side, we could be closer to the Sun, meaning higher temperatures, and thus the possibility of water being boiled away.
Life could exist – but it would be very different
Even if life could start, because of the powerful winds and extreme seasons, it would be very different than today because of the extreme conditions on Earth. Some sort of life forms would exist capable of withstanding extreme temperatures, high winds, and short days.
The smallest changes at the beginning of the evolutionary process can dramatically alter its course. Bacteria could easily adapt to these harsh conditions, of course, but complex life forms like humans – or even mammals would probably never evolve.
If complex life could find a way to evolve, evolution might favor short, stumpy creatures. Because if they stood tall, they would struggle to bear the extreme winds. Plants would also be short with long roots. There would be no trees, no rainforests, and their biodiversity.
The winds also would be very loud – so creatures would have to communicate in different ways, like changing colors of their skin to developing some sort of sign language. Ears would probably never evolve.
They could also use the strong winds as a travel method.
Without the moon, would there be life on earth?
A new study suggests “Planetary collision that formed the moon made life possible on Earth”
According to a new study, published by Rice University petrologists in the journal Science Advances, the planetary collision that formed the moon (also known as the “giant impact”, as mentioned above) made life possible on Earth.
Scientists say the Earth most likely received the bulk of its carbon, nitrogen and other life-essential volatile elements from the planetary collision that created the moon.
These are the essential elements that make life on Earth possible, and they are not native to Earth. In fact, in the beginning, all inner rocky planets in the inner solar system (Mercury, Venus, Earth, and Mars) were volatile-depleted.
According to study co-author Rajdeep Dasgupta, “the timing and mechanism of volatile delivery have been hotly debated”. He adds their research is “the first scenario that can explain the timing and delivery in a way that is consistent with all of the geochemical evidence.”
Scientists were thinking that these elements were delivered by the asteroid and comet impacts. But, there’s nearly twice as much carbon on Earth than there would be if these elements came from these objects.
The researchers created a computer simulation that modeled the chaos of the early solar system and ran it around a billion times. They then looked through the results to see what could have caused the chemical ratios in Earth bulk silicate.
Their findings suggest that “a rocky, Earth-like planet gets more chances to acquire life-essential elements if it forms and grows from giant impacts with planets that have sampled different building blocks, perhaps from different parts of a protoplanetary disk.”
Dasgupta adds: “this removes some boundary conditions. It shows that life-essential volatiles can arrive at the surface layers of a planet, even if they were produced on planetary bodies that underwent core formation under very different conditions.”
2. Without moon, the tilt of the axis of Earth would not be that stable
The seasons exist because Earth’s axis is today tilted 23.5 degrees from the plane of its orbit around the sun. But this tilt changes. During a cycle that averages about 40,000 years, the tilt of the axis varies between 22.1 and 24.5 degrees. Because this tilt changes, the seasons as we know them can become exaggerated. More tilt means more severe seasons-warmer summers and colder winters; less tilt means less severe seasons-cooler summers and milder winters. For half of the Earth tilted towards the Sun, one hemisphere receives more solar radiation from the Sun than the other. In the image above, it’s summer in the southern hemisphere, while it’s winter in the northern hemisphere.
The tilt of our planet’s axis would vary over time dramatically without a moon. This could create some very extreme seasons and weather conditions. Thanks to our Moon, the tilt of the axis is very stable – it only varies between 22.1 and 24.5 degrees during a cycle that averages about 40,000 years. Currently, it is 23.5 degrees.
As the tilt of our planet’s axis varies wildly, the poles wouldn’t always be cold and the equator might not always be warm. Without our Moon to stabilize us, ice ages would preferentially hit different parts of our world every few thousand years.
Why the axis of Earth would vary without the moon? You can watch the video below to find out.
Some experts estimate that Jupiter could help keep Earth’s tilt from reeling completely out of control. Letꞌs say that one day in its orbit the Earth’s axis just happens to point away from the sun, and Jupiter is hanging out in that direction at the same time. And let’s say that happens again … and again … and again. Every time Earth’s axis and Jupiter line up, it gets a super-tiny gravitational pull. At first it’s nothing. But over millions of years it can add up. Before you know it, the accumulation of tugs has flipped the Earth over.
3. The days would be much shorter – causing strong storms
When the moon was formed, the length of an average Earth day was just 6 hours. Moon slows down the rotation of Earth – and in around 4.5 billion years, now a day is 24 hours long. If the days were still six-hour-long, powerful winds up to 200 mph (322 km/h) would be a norm as a result of the rapid rotation of our planet.
4. Nights would be much darker
Without a moon, nights would be much darker. The full moon is around 14,000 times brighter than Venus, which is the next closest planetary body to Earth after the moon.
This could be a good thing for astronomers as the stargazing would be spectacular, but, unfortunately, there would be no astronomers to take advantage of these dark skies as the complex life forms like humans could probably never evolve.