E.T. But not nice about it.

I was recently pondering other worlds and what extraterrestrial life will be like, if we ever find any.

My bet is we will find some kind of life on Mars. Not little green men of course, but bacteria or maybe something larger. The probes have found nothing yet, but I heard a scientist on the radio explaining how she had taken a probe into a US Desert, and it had found nothing! And that is an area that has plenty of life.

It seems pretty certain that Mars had free water at some point in its history, and it was there long enough to carve river valleys and gorges. Free water means life is highly possible if not highly probable. And one thing we know from our own planet is life is very , very, persistent. Some of the most inhospitable places on Earth have life that has somehow adapted itself to the most hostile environments.

Which means if there ever was life on Mars, it’s probably still there.

But I was imagining something far more bizarre. Could a planet develop only animal life i.e. no plants! It’s quite easy to imagine the opposite but a planet without plant life?

Well it is possible (just about). Every creature from the smallest to the largest would have to be a predator. Without a base of herbivores, life would be competitive in the extreme. Every animal would have to aggressive and defensive. Every “cow” would need fangs and claws!

 But there is a major stumbling block – oxygen. Our animal life is based on oxygen and all of the oxygen in our atmosphere comes from, you guessed it, plants. Oxygen is a very highly reactive gas. That’s how we animals can “burn” it for energy.  It reacts with almost everything, so it’s very unlikely to occur naturally as a free gas. So the alarming denizens of our predator planet could not have a metabolism based on oxygen.

So, is there another highly reactive gas that occurs naturally? Well yes, there are a couple. One is sulphur dioxide. It is produced in vast amounts by volcanoes. It’s pretty reactive and forms sulphuric acid in contact with water.

But I think a more satisfying candidate is chlorine. Unlike Sulphur dioxide, It’s an element like oxygen. It’s very highly reactive.  And I believe it already occurs naturally in the atmosphere of some planets.

What an intriguing thought! A planet with a green atmosphere, populated by ravening beasts that would look and behave differently from anything we know - or can easily envisage. The evolutionary pressures would be extreme with just about everything trying to eat everything else.

Would that very extreme natural selection produce more intelligent life, faster? Or would such extreme savagery mean intelligence was a luxury no animal could afford?   I’m inclined to the former view. After all intelligence is just another environmental niche to be filled, and I would imagine extreme selection would fill them all very quickly.

I’m not a biologist so I don’t know if Chlorine is sufficiently reactive to support organisms or if a carnivore only ecosystem could exist. If you have any thoughts on this, put ‘em down below, in the comments box.