On The Moon

There are more human-made objects on the Moon than anywhere else in the Universe (with one obvious exception). You won't be able to see this stuff from Earth, but you can learn where we've left it.

Our Moon is tidally-locked, which means that the same side is always facing the Earth. Most missions, particularly the early ones, were sent to locations on the side that we can see - so that they would be easy to communicate with. Any objects on the other side of the moon (far side or the more poetic than accurately named dark side) would never see the Earth, and would not be able to make direct radio contact.

Let's start with just a few significant firsts in lunar exploration. Note that this is the view of the Moon from the northern hemisphere. If you're in the southern hemisphere your view will be rotated 180 degrees.

Luna-9 (1966) This was the first mission to achieve a soft-landing on the Moon - which is to say it survived the impact.
Apollo-11 (1969) The most famous lunar mission to-date - when humans first walked on the Moon.
Luna-16 (1970) This was the first automated return of soil from the lunar surface (although humans returned soil with Apollo 11 and 12 before this mission).
Luna-17 (1970) This included the first robotic rover on the Moon: Lunokhod 1.

Of course every mission to the Moon was an incredible achievement - even the ones that were only partially successful - and almost every one was a first for something. There are lots sites where you can read about the different missions, so it's worth having a look to see if anything catches your imagination. If you specifically want to have a go at memorizing all off the Apollo landing sites (there were only six), then the sky and telescope site has a good description.

Latitude and Longitude

You might be aware that locations on the Earth can be described in terms of a latitude (a measure of North-South) andlongitude (a measure of East-West). The equator on the Earth defines zero latitude (halfway between north and south poles), and for historical reasons zero longitude (called the prime meridian) sits at the location of the Royal Observatory in Greenwich, United Kingdom. Incidentally the two lines cross (marking zero latitude and longitude) in the sea just off the coast of West Africa.

The same is true for the Moon, although they're given a fancier title of Selenographic Coordinates. The tidally locked nature of the Moon is also apparent here, since whenever you look at a full moon the location of zero latitude and longitude will be roughly in the middle. I say roughly just because your perspective might change a bit, not because the centre is roughly marked. They're very precise about it.

coordinates of the moon with 0 at the centre middle Selenographic coordinates (Moon latitude and longitude). By John Reid via Wikipedia.

So now whenever you see the coordinates of something of something on the Moon (such as on Wikipedia), you'll have a rough idea of where it is. For example the recent Chang'e 3 lander set down at 44.12°N 19.51°W. That is roughly 44 degrees north of zero, and 20 degrees west of zero. Hopefully you can read that off in the diagram above - go left of zero to the 20, then follow the curved line up to the second blue line (40).

Lunar Features

We can't really spend time looking at locations on the Moon and ignore the geographical features. Again we'll focus on just four - this time some of the most visible craters. Move the mouse pointer over over each of the circles to see the name.

As is often the case, the four craters shown are all named after astronomers. The most obvious is Tycho in the south (assuming you're in the northern hemisphere), named after Danish astronomer Tycho Brahe, which is estimated to have been caused by an impact that occurred 108 million years ago. The three bunched close together (relatively speaking) are named after Johannes Kelper, Nicolaus Copernicus and Aristarchus of Samos.

The dark patches on the Moon's surface are known as Mare (Latin for Sea), but I feel like we've already drifted too far from the topic of this post to go into them in detail. Also, because the names are in Latin, and sound more like spells from Harry Potter, I find them difficult to remember. However, probably the most famous is the one that Apollo 11 landed on the edge of (see the first diagram on this page for the location of the Apollo 11 landing site). This was the Mare Tranquillitatis, which translates in English to the Sea of Tranquillity.

Google Moon

Arguably the best tool for exploring the Moon is the the Google Earth application. A button in the top-middle of the window allows you to switch from viewing the Earth, to look at the Sky (stars), Mars or the Moon.

Switching Google Earth to the Moon view. Switching Google Earth to the Moon view.

The information is very detailed. You can search for certain missions or features, access multimedia resources, view 3D models of some of the spacecraft, and much more. The image below shows the Apollo 15 landing site, which was the first mission to use the lunar rover. The black lines show the routes that the astronauts drove the rover along, and there are also icons that you can click on to view the photographs and videos taken from specific spots.

Google Earth viewing the Apollo 15 landing site. Google Earth viewing the Apollo 15 landing site - with rover tracks.

Hopefully now when you look up at the Moon you will view it differently. It does take some complicated engineering and science to get there, but decades of work has proven that it is within our reach. And it is no longer limited to countries, since the Google Lunar X Prize is showing that private organisations can develop the technology needed. We continue to send robots to explore the Moon, and soon humans might return there to. You could even be amongst them.