 Greetings and welcome to the Introduction to Astronomy. In this week's Exploration of the Solar System we are going to talk about some of the Luna spacecraft series, and in this case specifically Luna 10 through 14. So these were, as you may guess by the name, intended to explore the Moon. Now several of these, in fact, Lunas 10, 11 and 12 and 14 were all orbiters, meaning they were orbiting the Moon. And they were launched between March of 1966 and April of 1968. What was the reason for these? Well, they were trying to study some of the things like magnetic fields around the Moon, radiation belts, and what kind of dangers these might apply to future missions of humans to the Moon. One of the discoveries that were made were mass-cons. Now a mass-con is actually a mass concentration, so excess material, in certain areas around the Moon, excess mass below the surface. These could often be caused by things like meteorites. A heavy meteorite burrowing itself into the surface of the Moon would have extra mass there. Now for the most part that would not affect anything else. However, when you have a craft in orbit and it's close enough, those would affect the overall gravitational field of the Moon and would affect how that lunar craft orbits and could have major impacts on craft trying to land on the Moon. Another thing studied was how often the micrometeorites, very tiny pieces of material, would impact the spacecraft. Now those are things we don't have to worry about here on Earth because they are burned up in our atmosphere, so they never make it down to the surface of Earth. However, the Moon having essentially no atmosphere, they would make it down there. Now the Luna 13 spacecraft was a little bit different. This was actually a landing craft, and we can see where it landed here, and the lunas are in the red, and Luna 13 is off over here as to where it landed. So this was again a landing craft on the surface of the Moon and was the third successful landing in December of 1966. Now landing on the Moon, and specifically we mean soft landing here, is important because we wanted to study the soil of the Moon, and that was in preparation for landings on the Moon by humans. We wanted to know how thick the soil was and how so how far into the soil the craft would penetrate, and that was something that was not known for sure as how thick the lunar soil was. We really didn't know about that until we actually had craft soft land on the surface of the Moon. And as you see we're getting very close to human landings at this point just a few years away. Also, studying the radiation levels. So would there be dangerous radiation levels? Again, something we have to think about when sending humans to the Moon. For the robotic craft, it really doesn't matter so much as long as the radiation is not so intense that it would fry material there, fry material, fry electronics. But for humans going to the Moon, we want to make sure that the radiation levels were not too high. So as we continue to see now we're getting closer and closer to actually landing humans on the Moon and the lunar craft by the Soviet Union were some of the earlier studies of how this might work. So let's go ahead and finish up with the summary here. And what we've looked at is that the lunar craft 10-14 were launched in the mid to late 1960s and we're studying our Moon. Luna 13 is the one of these that landed on the surface. The other craft were designed to orbit and were never planned to land on the surface. And the knowledge gained here helped in preparation for future human landings on the Moon just a few years later. So that concludes this lecture on the Luna 10-14 spacecraft. We'll be back again next time for another exploration of the solar system. So until then, have a great day everyone and I will see you in class.