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Mars – Why does it not have life?

Ah, Mars. My favourite of the inner planets, because it is so close (astronomically speaking) but yet it is mostly a mystery to us, and it has such an interesting past. And this is exactly what we are going to talk about today.

Scientists think that once upon a time, a long time ago, Mars was once much like Earth. It had an atmosphere, it had water (in fact, they think the northern hemisphere was mostly covered whilst the southern was mostly land! Imagine a planet where all the northern hemisphere was water and all the southern was land, how cool would that be?) and, like Earth, to this day it still has seasons, weather and everything!

So, what happened?

Unfortunately, the one thing that Mars didn’t have which Earth did was a closer proximity to the Sun. This was its downfall.
A little back story for those who don’t know, Earth has magnetic field which is caused by the hot inner core of the planet spinning. This spinning created and sustains our magnetic field.
Mars also had a magnetic field back in the day, but it is now gone which is why things went wrong. Why doesn’t it have one anymore? I’ll tell you why.

As I previously mentioned, Mars was too far away from the Sun. Why do I say “too far”? Because it is colder than Earth. This change in temperature is great enough to allow the hot inner core to cool, and this cooling meant that it started to spin slower. And slower. And slower still. This continued until the core stopped spinning altogether. No spinning core means no magnetic field. And this, unfortunately, meant that Mars had no protection from the Suns solar winds. These solar winds obliterated most of the atmosphere on Mars. And that meant it couldn’t retain enough heat, like Earth does, to keep warm.

But I can already hear your next question. If Mars got ridiculously cold, why isn’t it covered in ice from that massive ocean that Chris just mentioned? Well, allow me to explain.
The loss in atmosphere and, because Mars is smaller than Earth, its weaker gravity, the pressure on the surface of Mars is so low, that if water was introduced, it would either rapidly freeze or it would rapidly evaporated. Cool, right? This is why I love Mars!

However, water can still be found on Mars, but as a solid. At either pole, there are polar water ice caps, again, much like Earth has. The main difference between Mars and Earth though is that the water ice at the poles on Mars are also covered in another type of ice. Carbon dioxide ice. It is so cold on Mars that carbon dioxide freezes in the Martian winter. And we thought British winter was chilly!

The carbon dioxide ice, however, does melt during the summer, increasing the atmospheric pressure. While this may lead to a peak temperature of about 20 degrees Celsius, the pressure change also causes dust storms that cover nearly the entire planet’s surface. Not so cool.

So, all in all, Mars? Not a great place for life. Not anymore, at least.

But, if scientists get a good hold of that whole “terraforming” thing and think they can return Mars to its former glory? Then book me a ticket on the closest and soonest shuttle please!


So that was the story of Mars! I hoped you guys enjoyed it and learnt something new. If you have any questions, leave a comment below and I will get back to you as soon as I can!

Published inAstrophysicsScience

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