1 What we’ve learned about the Moon

What struck me about lunar samples was how totally foreign they are to the materials I was used to. I've done a lot of field work. I've worked with granites, basalts, soils on Earth. But the things that I found in the first samples I saw from the Apollo 16 drill core were just stunning. Here were basalts, fragments of lava, that were almost four billion years old, and they were as fresh as if you'd collected them in Hawaii the day before. That just doesn't happen on Earth.

The Moon is a time capsule. It preserves rocks in states that just cannot be found on Earth. And that's one of the really intriguing things about the Moon, is it's a very, very old encyclopaedia. We can go back into events that occurred in the Solar System far earlier than the things that we're familiar with on Earth. We can see things that have happened that we have no record of on Earth. And in that regard, it's just a phenomenal repository of history. And when you get right down to it, at least in my perspective, geology is all about history on the very large scale. Not within the span of a human lifetime, but within the span of billions of years.

One of the key scientific questions that was in the forefront when the Apollo mission was being designed was, how did this thing form and what does it mean for us? Was it captured? Did it form along with us? Did it split off from the Earth? There is now something called a giant impact theory, the concept that a very large body at some point impacted the Earth. So there is an aspect of something coming from outside the Earth's regime, something then forming around the Earth as a result of the impact, and also with parts of it coming from the Earth. All of this seemed to play into this origin theory. And it's fascinating because no one had thought of stringing those things together. They were all considered separate, and the Moon was able to unify this.

The Earth is a complex system, and we still have poor understanding about what would happen if you tweaked part of that system. If you took away our Moon, what would really happen to the Earth? How would it have evolved? It would certainly be a different planet, but how different? Earth used to spin faster than it does now. And it has slowed down over time because of tidal drag from the Moon. It has affected the length of our day. It affects the cycles within the Earth's ocean. All of this shows up in the way that life has evolved on Earth - the way we adapt to day-night cycles, the way life in the ocean has developed. It has moderated the way that the Earth behaves in many ways. There should be many Earth-like planets out there. But we're really special because of this complex interaction and relationship we have with our Moon. It gives us a companion that steadies our dynamics in this habitable zone around the Sun. We don't have serious extremes of orientation that could really be a significant issue for creating an environment that is steady enough, stable enough, and favourable enough for life. And it's a real question - are we unique or not? How often does this happen? And how important is this relationship with our Moon? Is it really that critical? And I don't have the answer for that, and I don't think anyone else really does right now. But it's something that deserves really serious consideration, especially as we're looking at the role of Earth and life in the universe.