 Greetings and welcome to the Introduction to Astronomy. In this week's Exploration of the Solar System we are going to discuss the Mariner 4 spacecraft and what that was able to explore. So let's go ahead and take a look here. Now Mariner 4 was launched on November 28th of 1964 and its purpose was to explore the planet Mars. So this will be the first exploration of Mars that we've looked at and it took it a little, not quite a year to get there and launched on November 28th of 1964 and then closest approach to Mars on July 15th of 1965. And it was able to get some of the very earliest images and here is one of those very early images which doesn't look all that great but again this is the first close-up image that we're getting of Mars actually flying by Mars. And this was again a very rough one. We'll see some more processed ones in just a minute. So here we see this. Now what's a fly-by mission means that it did not go into orbit around Mars. Fly-by missions much easier to plan. You don't have to adjust the orbit. You just go to the planet, fly by it, take your pictures and then leave. So it was again a preparation for looking at future missions which would then orbit Mars and other planets. Now some of the findings included terrain that looked much like that of our own moon. So here's a little more processed image and we can definitely see regions of distinct craters. So we can see those craters there and in fact in places craters on top of craters. So the moon is very heavily cratered and has craters all over its surface. Mars has some areas that are very heavily cratered and some that are much lighter craters. So it has a much more varied types of terrain on it. Now Mariner 4 was also able to measure that Mars had a very low atmospheric pressure, much lower than Earth's, very cold temperatures and no magnetic field or radiation belts. And one thing Mariner 4 was able to confirm was that there was no liquid water currently on Mars. So that was something that we again had considered for a long time. Could there be life on Mars? Well, as we know it, life requires liquid water. So unless there is some strange type of life that lives without liquid water, really water is something very important for life and ruling out liquid water on Mars really ruled out a lot of chances that life or complex life currently existed. And in fact the Mariner 4 spacecraft was able to conclude definitively that there could be no intelligent life on Mars. Now we still search for life now. So the idea that there might be life on Mars of some simple type is something we still look for today. And we do know that there is or was water on Mars in the past. However, the initial findings of Mariner 4 put a lot of things to rest that we had thought maybe for decades before this about the possibility of life or even some kind of civilization on Mars. Now the mission ended a couple of years later when transmissions were lost due to micrometeoroid impacts that damaged the craft as it continued traveling out through the outer parts of the solar system. But it was really our first close-up look at the planet Mars. So let's finish up with our summary here. And what we saw is that Mariner 4 did give us our first close-up look at the planet Mars. Flying by Mars in July of 1965. And the observations were sufficient to determine that intelligent life would not be possible on Mars. So that concludes this lecture on Mariner 4 spacecraft. We'll be back again next week for another exploration of the solar system. So until then, have a great day everyone, and I will see you in class.