Have you ever looked up at the night sky and wondered why we are the only planet with life?
Earth is the third planet of eight that make up our solar system. Why isn’t there life on Mars, Venus or Jupiter?
There are a few crucial factors that allow Earth to support life, and leave other planets barren. And they can be explained with the ‘Goldilocks Paradox’.
Distance From The Sun
Life as we know it needs a few things in order to exist. Most importantly is the presence of liquid water. This is determined by the planet’s distance from its star. If a planet does exist in a star’s habitable zone, or ‘Goldilocks zone,’ and atmospheric conditions allow for liquid water to be present – then life may form.
Planets like Venus, that are closer to the sun than us, are unable to host life because they’re simply too hot. Liquid water can’t exist on these planets – and water is essential to life.
Other planets that are further from the sun than us are too cold so only water in the form of ice exists. Or they may even be made entirely of gas like Neptune and Uranus.
Earth, fortunately for us, is just the right distance from the sun. Not too far, not too close.
Another necessary characteristic is the presence of an atmosphere.
The atmosphere helps to keep the planet warm through the greenhouse effect. It absorbs harmful solar radiation and reduces the temperature changes between day and night.
Venus has an atmosphere, but since it is so close to the sun, an out-of-control greenhouse effect takes place on the planet’s surface. Making it too hot to be hospitable for life at 462 degrees Celsius!
Mars used to have an atmosphere, but it has long since disappeared (see below for why).
SO once again, planet Earth’s atmosphere is just right.
As well being able to form an atmosphere, a planet must be large enough to have a gravitational pull sufficient to keep the atmosphere around the planet.
Venus did not have a problem with this, as it’s a similar size to Earth. But Mars was too small to hold-on to it’s atmosphere, which disappeared a long time ago. Without an atmosphere, life cannot exist.
Once again – Earth is just right.
Luckily for us, with the Earth’s solid inner core and partially molten outer core there is a strong magnetic field around the Earth and tectonic activity in the mantle and crust.
The magnetic field deflects extremely harmful UV rays and the tectonic activity helps feed the atmosphere and ocean with nutrients.
Life Is Special In Our Universe
If you wanted to find life out in the vast universe you would need to find a planet a Goldilocks planet, not too hot or too cold, similar size to Earth, and with just enough water.