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What’s On The Far Side Of The Moon?

You probably know we only see one side of the Moon from the Earth. But for the majority of human history, we had no idea what the far side looked like.

Billions of years ago, our Moon was formed when a Mars-sized object smashed into the Earth, spinning out a ring of debris. This debris collected into the Moon we know today. It started out rotating from our perspective, but the Earth’s gravity slowed it down until its rotation became locked with the Earth’s, keeping one half forever hidden from our view.

The dramatic difference between near side and far side shows up in this much more recent global map of the map made by Clementine Mission in 1994. The map is centered on the near side with its many lunar "seas" or maria. The far side trails off to the left and right of center. Mare Moscoviense is at upper right. Credit: NASA

The dramatic difference between near side and far side shows up in this much more recent global map of the map made by Clementine Mission in 1994. The map is centered on the near side with its many lunar “seas” or maria. The far side trails off to the left and right of center. Mare Moscoviense is at upper right. Credit: NASA

It wasn’t until the space age that humans finally got a chance to see what’s on the other side. The first spacecraft to image the far side of the Moon was the Soviet Luna 3 probe in 1959, which returned 18 usable images to scientists. And then in 1965, the Soviet Zond 3 transmitted another 25 pictures of higher quality that gave much more detail of the surface. The first humans to actually see the far side with their own eyes, were the crew of Apollo 8, who did a flyover in 1968.

We now have high resolution cameras imaging every square meter, even the far side. And here’s the amazing surprise….

You would think that the far side of the Moon would look like the near side, but check out the two hemispheres…They’re totally different.

The near side of the has huge regions of ancient lava flows, called maria. While the far side is almost entirely covered in crater impacts. Planetary geologists aren’t sure, but it’s possible that the Earth used to have two Moons.

Billions of years ago, the second, smaller moon crashed into the far side of the Moon, covering up the darker maria regions.

And just to clarify things with Pink Floyd’s reference to the “Dark Side of the Moon”… Except for the occasional lunar eclipse, half of the Moon is always in darkness and half is always illuminated. But that illuminated half changes as the Moon orbits around us.

High resolution photo map of the moon's far side imaged by NASA's Lunar Reconnaissance Orbiter. Mare Moscoviense lies at upper left and Tsiolkovsky at lower left. Click for a hi res image. Credit: NASA

High resolution photo map of the moon’s far side imaged by NASA’s Lunar Reconnaissance Orbiter. Credit: NASA

Just like half of the Earth is always in darkness, and half of every other large object in the Solar System. There’s no permanent “dark side” of the Moon. The side facing towards the Sun is lit up, and the side facing away is in shadows.

There are, however, some spots on the Moon which are in eternal darkness. There are craters at the north and south poles deep enough that the light from the Sun never illuminates their floors. In these places, It’s possible that there are reserves of ice that future space colonies could use for their supplies of water, air, and even rocket fuel.

Pink Floyd was right if you’re talking radio waves instead of visible light. The far side of the Moon is naturally shielded from the Earth’s radio transmissions, so it makes an ideal spot to locate a sensitive radio observatory.

I’ll see you in the permanently shadowed craters of the Moon.

About 

Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

Comments on this entry are closed.

  • Astrubal January 16, 2014, 6:12 PM

    “[…] reserves of ice that future space colonies could use for their supplies of water, air, and even rocket fuel” !

    Is it a joke? No… never ever, I hope!

    In that ice are stored 4,5 billions invaluable Solar system archives. Using that ice for water or rocket fuel would be a crime against science (and maybe against humanity).

    • Sonny_Taylor January 17, 2014, 7:33 AM

      Assuming that a considerable mass of water (ice) is there, only a small sample would be needed to unlock the ancient 4.5 billion year old archive you speak of. Much of the rest might be put to good use.

      Perhaps we shouldn’t have touched a drop of water on Earth. How old do you think most of it is?

      • Astrubal January 17, 2014, 8:24 AM

        1.- You assume “that a considerable mass of water (ice) is there”, but you don’t know. And nobody knows yet for sure how deep is that ice layer.

        2.- I won’t comment this: “only a small sample would be needed” :)

        3.- I think there is a confusion between the terrestrial water mixed and remixed during time with the 4.5 billion years of “deposit” in these craters. Even layers of ice in the Earth’s poles can not be compared with that sort of concentrated layers of the lunar ice (with all what is trapped inside since billions of years). And that’s why it’s invaluable archives.

        4.- And if I’m wrong, it does not matter. At least, I remain cautious about what I consider to be a scientific treasure.

    • Fraser Cain January 17, 2014, 10:32 AM

      Of course we’re going to be using these stores of water ice for rocket fuel and other purposes. You don’t need much for research, and without air on the Moon, it won’t be accidentally contaminated. Those resources will be used to help more scientists get to the Moon to study it.

    • David D January 19, 2014, 10:46 AM

      If civilization is to survive humanity must get off the earth. To do this people will have to make money doing it or it won’t happen.
      As far as water on the moon is concerned it could be imported by crashing a comet into the moon. All that is required is to heat the comet ice, direct the steam-thrust and steer the comet to its future reservoir.
      If humanity doesn’t leave earth our race will die a slow death in poverty on a depleted planet.

  • tenstripe January 16, 2014, 6:23 PM

    A radio observatory without the Earth’s noise would be a great mission; and it could be done unmanned on the cheap. Of course, you would still need to solve the communications problem. Dark side of the moon will forever role off the tongue. It’s still a place that we can’t sometimes see from earth. The far side is somewhere I wouldn’t want to live.

  • John Santucci January 16, 2014, 8:35 PM

    I know someone in his late sixties who claims that absolutely NO humans have seen the darkside of the moon per an agreement we have with “them”, the aliens , to never venture there as they have a base of operations there. He is so positive that NO probes or manned craft ever been there and any alleged photo’s are just made up. All the astronauts are told to say they been there. Anyone claiming otherwise has been silenced. Oh, and other reason for no other manned landing missions on the moon was aliens requested this or else. China’s mission is another movie set. Seriously. He is adamant. He says a lot of people know this a 100% fact. Astronomers know this as fact and have all been ordered to go along with the cover up, or else. Yes. He said that this has been cover thoroughly on the internet.

    • Olaf2 January 17, 2014, 4:35 PM

      You could debunk him immediately by showing that the “dark” side moves around the moon in 28 days. So those aliens must be nomades to stay in the dark. LOL

  • Bill McLaughlin January 17, 2014, 10:37 AM

    Well, Duuh, clearly the secret Nazi Moon base ala “Iron Sky”!

  • SHREEKANT January 17, 2014, 5:22 PM

    I am here to contradict the collision theory for moon formation. Actually moon formed just after, better to say simultaneously with the formation of earth. The large number of crater on the other side of the moon is due to more gravity at that side and more shielding from earth side. The most of the craters were made when moon was too hot.

    my model of solar system formation is based on the dark energy & dark matter consideration

    http://swarajgroups.blogspot.in/2013/06/out-of-box-thinking-is-essential-in.html

    swarajgroups.blogspot.in

  • David D January 19, 2014, 10:37 AM

    Google can send a robot to the moon to claim it under Marine salvage law. If they don’t get a space ship they can establish a mining claim. Either way, there is money to be made on the moon if companies can get over the initial investment hurdle.

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