蜜桃恋人

The Far Side of the Moon

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Caption

Near Side of the Moon on the left and Far Side of the Moon on the right.

Photo Credit
NASA

The same side of the Moon always faces Earth. So what's on the far side?

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We never see the far side of the Moon or what some people mistakenly call the 鈥渄ark side.鈥 So what can we see on the lunar far side? Does it looks identical to the near side to Earth?

First, it鈥檚 important to know that we always see the same side of the Moon from Earth鈥檚 surface鈥攚hat we call the 鈥渘ear鈥 side of the Moon versus the 鈥渇ar鈥 side of the Moon. 

This is because the Moon鈥檚 orbital period is the same as its rotation around its axis. Our planet鈥檚 satellite is tidally locked to Earth, which means it rotates on its axis at the exact same rate that it orbits Earth. 

Discoving the Far Side of the Moon

On October 4,1959, Russia鈥檚 Luna 3 spacecraft was launched towards the Moon, where it later became the first vehicle to send back the very first images of the Moon鈥檚 far side.

Surprise!

The far side looks a lot like the near side. But not exactly.

  • Like the side of the Moon we see, the far side of the Moon is also lit up by the Sun or it鈥檚 in shade. It鈥檚 not 鈥渄ark鈥 just because we can鈥檛 see it. Every part of the Moon has both day and night in half鈥搈onth intervals. 
     
  • On the near side, we see large, dark seas of cooled lava, called maria, that cover a substantial fraction of the surface. But this lava is absent on the far side which, instead, features many impact craters鈥攕cars received during its first few hundred million years of life.

    We now know that 35% of the Moon鈥檚 Earth-facing hemisphere is covered with molten material, but only 1% made it to the far side. The far side鈥檚 crust is also significantly thicker than the near side, perhaps due to the number of impact craters.

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Image: First Photo of the Lunar Farside. Credit: NASA.

Seeing the Far Side 

Since 1959, several missions by NASA and other space agencies have shown us more of the Moon鈥檚 far side. 

In December of 1968, the Moon鈥檚 far side was finally seen with human eyes by the crew of Apollo 8 during their historic circumlunar flight.

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Image: Rough terrain on the lunar far side photographed by Apollo 8. Credit: NASA.

Below is another image of the fully-illuminated far side of the Moon that is not visible from Earth. These were captured by NASA鈥檚 DSCOVR satellite on July 15, 2015. Twice a year, the satellite is about to capture images of the Moon and Earth together as its own orbit crosses the orbital plane of the Moon. 

On the far side, you can easily see the Mare Moscoviense (Sea of Moscow) and the Tsiolkovskiy crater. Many features on the far side of the Moon retain the Russian names given to them by Soviet scientists.

Note that the Earth鈥檚 North Pole is toward the upper left, based on the angle of the satellite鈥檚 camera.

The Far Side or the Dark Side?

Apologies to Pink Floyd: There is no continually dark 鈥渟ide鈥 of the Moon.

Both near and dark sides have the 鈥減hases鈥 of the Moon with the same cycle of illumination.

Here鈥檚 a fun fact:  It鈥檚 our near side of the Moon that actually reflects less light than the far side because our side has lots of dark, smooth, low-lying plains (from ancient seas of molten magma) that do not reflect the light as well.

So, the near side is the dark(er) side!  Click here to read about the 鈥Near Side of the Moon.鈥

Below are images of the Moon. The near side is on the left/top and the far side is on the right/bottom Which side looks darker to you?

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Tips on Viewing the Moon

Look at the near side yourself! If you have binoculars, look at the Moon during dusk before the Moon is too bright in the dark sky. You should be able to see those dark lunar lowlands.

The best time to see the Moon is not during the full Moon. It鈥檚 easiest to see during the Moon鈥檚 crescent or gibbous phase. See my post on the Quarter Moon.

Check your local Moon Calendar to know tonight鈥檚 Moon phase

About The Author

Bob Berman

Bob Berman, astronomer editor for The Old Farmer鈥檚 蜜桃恋人, covers everything under the Sun (and Moon)! Bob is the world鈥檚 most widely read astronomer and has written ten popular books. Read More from Bob Berman