Oh Moon, not just for lovers,
You shine for us all lifers
That beauty you fill us blunt
Not just for the hunt
But for humane seasons
In the end we grasped with reason
The Moon holds our hand
Across space to no end
Our celestial mate
Our own hand of fate
Earth’s Moon is most peculiar. It is large relative to the planet it orbits around. Nearly as large as the three largest satellites in the Solar System: Ganymede, Titan, Callisto. Those orbit giant planets.
The Moon has made advanced life on Earth possible. Maybe if Mars had a large moon, it would enjoy obvious life now: a moon would have made super summers impossible.
If one considers Mercury, Venus and Mars, there is something very wrong with their diurnal rotation: it is either way too slow, or way too wobbly, in the fullness of time. Even if Venus did not have a killer CO2 atmosphere, it’s very slow (counterclockwise) rotation would have scorched, half freeze life there, on a perpetual basis.
Mars rotates on itself in roughly one Earth day, but the axis of rotation does not just precess (as it does on Earth). It also changes inclination on the plane of rotation of the planets (the “Ecliptic”). And does so wildly. This means that, periodically, Mars has super summers (and super winters). During super summers, a lot of water vapor appears in the atmosphere, and that’s a powerful greenhouse gas (actually more powerful than CO2).
The Moon-Earth system has one global angular momentum: as the Earth’s rotation slows down, due to the friction of the tides, Earth’s angular momentum goes down, so the angular momentum stored by the Moon has to go up. That’s mostly stored in the product of the distance of the Moon, times its mass, times its speed. The only of these three factors which can go up is the distance of the Moon: so the Moon, which used to be very close to Earth, is now roughly at one light second.
NASA confirmed today what we already knew: there is briny water flowing on Mars. It’s liquid at minus twenty degrees Celsius (being full of anti-freeze). It’s exact origin is still unknown: deliquescence, melting permafrost, watery reservoirs?
It has long been known there is plenty of water on Mars. It’s just frozen in the ground, and at the poles. During super summer, the poles probably disappear, and there is much more water and warmth on the planet. It’s not excluded that life blossoms then.
Super seasons would have been be a killer for Earth’s advanced life, periodically over-heating or freezing the ocean.
Where from this orbiting celestial miracle?
The Moon is made of Earth. Science does not explain that yet. The main theory’s base state claims that the Moon is collision debris: Earth would have collided with a third body, Mars size, and the orbiting debris would have gathered into the Moon.
I even have my own theory, both outlandish and Politically Incorrect: a succession of nuclear-assisted explosions would have lifted material at the Roche limit, where it would have gathered, forming the Moon.
Angular momentum would have done the rest. Pro my theory: we have a massive, life-giving nuclear fission reactor below our feet. It rotates an iron ocean which in turn generates a life saving magnetic shield. It also generate plate tectonic and mantle subduction, which burrows all nefarious fossil fuels, and excess CO2. (That worked well until the oil devils took over!)
Could we have life on Earth without our large Moon?
This is not clear. Not at all. Having a stable rotation axis is primordial. One of our Solar System gas giant’s rotation axis is nearly within the plane of the ecliptic. Something happened to tilt it. Gas giants can be tilted. Yet, the Earth would be hard to tilt, because of the Moon.