The Editor's Corner
Studying the other planets of the solar system tends to make you think what an ideal place the Earth is for life to have evolved. Of course it’s an anthropic argument; our home planet suits us since we evolved to live here and if it wasn’t suitable we wouldn’t be here to debate it! But when we look at the other planets in our own solar system the Earth does have a number of unique features that make it a great place for an experiment in applied biology on a grandiose scale.
Convection currents within the Earth’s liquid iron core generate a global magnetic field that deflects the energetic charged particles of the solar wind away from ourselves and our atmosphere. Planets such as Mars and Venus that don’t have such a global field are bombarded with radiation at far higher levels than the Earth. Of course life can evolve to survive in higher radiation environments but you can’t avoid the essential physics. Radiation damages DNA and if the dose is high enough no amount of repair mechanisms can keep ahead.
The Earth has a mantle with just the right composition for tectonic plate movement. Although the collision and subduction process can be violent in places it provides a mechanism for releasing excess heat built up in the mantle. On planets such as Venus that don’t appear to have this process heat builds up to the point where entire crust weakens and massive phases of vulcanism obliterate the entire surface of the planet every 500 million years. Bad news if you’re an evolving organism!
The Earth also has a huge moon compared to the other terrestrial planets. This is far more important than many people realise because it generates big tides in the oceans. Many early marine organisms would have been left stranded on the beach by this tidal action and this may well have been a major factor in the evolution of air breathing animals.
I think the moon has also been really important in shaping the development of human thought. Having such a large bright and obvious thing progressing through its phases in the sky is a graphic demonstration of the nature of large bodies in space. Seeing regions of a spherical moon go from light to dark would have to have inspired the idea that the Earth too must be round and night and day were its phases.
When the first telescopes were turned to the moon the mountainous landscape must have been reminiscent of regions of the Earth. It wouldn’t take a huge leap of imagination to see our own world as perhaps one of many in the vastness of space. Even today I think one of the coolest things you can see is a half moon through a really good quality telescope. It’s truly amazing and something everyone should see it at least once in their lifetime!