Alexandra Grassian (03/10/04)
What surprised me the most from our discussion on Monday was how much planets can change over time. It is hard to believe that at one point Mars might have had oceans flowing over the majority of its land, and much warmer temperatures than currently exist. It made me think about what the Earth might look like in 100 million years or so – will it become more Mars-like? Plate-tectonics seem to play a huge role in the evolution of planets, and if one day the earth cools enough so that it only has one plate, it is not inconceivable to believe that one day Mars might be more hospitable than Earth. And this also means that Mars could change drastically as well. For these reasons, I really do believe that it is important that we continue to explore the other planets – especially Mars, due to its similarity to Earth.
But there are many differences between Earth and Mars. One of the most drastic differences seems to be the fact that Earth has the Moon revolving around it, while Mars does not. I never before realized how much the Moon affects the Earth – by moderating the obliquity changes and the Mars actually formed from a large impact with the Earth. How exactly does the Moon moderate obliquity changes on the Earth? Also, what sort of chemical implications are involved from the fact that the Moon and the Earth were once one body? Does this make the Moon much more chemically similar to the Earth than most other planets/moons are? And, if so, in which ways?
I was also thinking more about the plate tectonics. What evidence, if any, is there that Mars once had more than one plate? And, is it possible, that if when the plates cooled and hardened to become one, water could have become trapped beneath them? By looking at the phase diagram for water, I noticed that in order for liquid water to ever be able to again exist on Mars' surface, but the average temperature and the pressure would have to change – the increase of just one would not suffice. This means that it would take more than just a huge volcanic eruption to bring about this change.
Also, even though we now have very conclusive evidence that water did exist in large amounts on the surface of Mars, I was wondering if we have any idea how this water behaved. For at different pressures and temperatures, water can behave very differently and I was thinking that this might affect how the water interacts with other molecules. If the average temperature was much lower than it is on Earth there would not be much available energy for complex molecular reactions, which are often needed to produce organic compounds.Even though all these questions are fascinating, I cannot yet rationalize spending quite so much money on the exploration of Mars when we have so many problems right here on Earth that need to be solved. There are so many diseases that do not have nearly enough resources to do research at any reasonable speed. And there are numerous people who go hungry everyday and don't have a place to live. But I don't think we should stop efforts altogether either. Just make sure we focus attentions elsewhere as well.