... that because of Mars' small size, it cooled faster, thus freezing its outer core and shutting down its dynamo? Isn't Venus the far greater mystery? Nearly the same size as Earth, yet no magnetic field and what appears to be occasional whole-crust overturn rather than plate tectonics? Isn't that the one we need to solve?
... that because of Mars' small size, it cooled faster, thus freezing its outer core and shutting down its dynamo? Isn't Venus the far greater mystery? Nearly the same size as Earth, yet no magnetic field and what appears to be occasional whole-crust overturn rather than plate tectonics? Isn't that the one we need to solve?
Well, I think they have Venus figured out. Basically it was like us early on, complete with oceans and land and magnetic field. Back in the beginning of the solar system, the sun was cooler than it is today. As it ages it grows hotter, like in the next 1 billion years the sun will be 10% hotter. Well, as it grew hotter back then, Venus's oceans started to evaporate into the atmosphere, and the H20 became lost to space. Leaving an ever growing thick atmosphere that held in the heat and increased the pressure on the surface. Being closer to sun, as it grew hotter, it also was moving closer to the edge of the habitable zone, which was moving outward as sun grew hotter. Without water on the surface anymore, plate tectonics stopped completely. When this happened, you no longer get a nice moderate release of volcanism, you get trememdous pressure building up and then released in huge amounts all at once probably every 400 million years that covers the planet in liquid hot magma. Also, it looks like Venus got hit hard by another proto planet that unlike what happened to the earth, which was a glancing blow at angle, Venus got hit straight on, slowing down it's spin a lot, It's one of(maybe the slowest), slowest spinning bodies in our solar system. I think you couple that with the lack of water to keep plate tectonics moving, you end up disrupting it's dynamo in the core and you have a very weak magnetic field now. The Earth is going to become Venus as the sun grows hotter and the habitable zone moves out further. It's a long time from now, but it will happen.
Base 8 is just like base 10, if you are missing two fingers. -- Tom Lehrer