Hello, friends!

So I’ve fallen down a research rabbit hole, or maybe I should say I’ve fallen into a research crater.  I’ve been studying the topography of the Moon: mountains, valleys, craters, cliffs, etc, etc.  Some of these lunar land forms sound like they are stupidly big.  2 or 3 kilometers tall, in a surprising number of cases, or 2 or 3 kilometers deep.  Photos taken from space or by Earth-based telescopes don’t necessarily give you a good sense of just how stupidly large these things are.

Of course we have stupidly large land forms here on Earth, too.  Mt. Everest rises about 8.5 kilometers above sea level, and Mauna Kea (in Hawaii) stands more than 10 kilometers above the ocean floor.  The tallest mountains I’ve seen, personally, would be the Rocky Mountains in the western United States.  According to the Google machine, the tallest of the Rocky Mountains stands about 4 kilometers above sea level; however, if you’re in a place where you can see the Rockies, you’re not standing at sea level.  So I’m guessing that when I saw them, the Rocky Mountains were looming roughly 2 or 3 kilometers over me—comparable to many of the lunar land forms I’ve been reading about.

But here on Earth, mountains like the Rockies or the Alps are exceptional, whereas on the Moon, mountains that big (or cliffs that tall, or craters that deep) seem to be fairly ordinary.  I’m guessing this is due to gravity.  It’s easier to be a big mountain when the pull of gravity is so much less.

So if you and I were standing on the surface of the Moon, is that what the landscape would look like around us?  Rocky Mountain size mountains all around us?  In some regions, yes.  But also no.  Before you try to imagine what the lunar landscape would actually look like, to your human eyes, I need to tell you how your human eyes may play tricks on you when you’re on the Moon.

Here on Earth, when you see a tall mountain in the distance, how can you tell it’s a tall mountain in the distance and not a small hill right in front of you?  Well, certain visual cues help your brain figure that out.  Roads and cars, trees and buildings, birds or other wildlife… you know how big or small these things are, and seeing these things will help you guesstimate how large a nearby hill/far off mountain must be.

The atmosphere also plays a role in this.  Air is not 100% transparent, so even on a clear and sunny day, distant mountains will tend to look a little hazy—noticeably hazier than a nearby hill would look.

But there’s no air on the Moon, so you won’t see any atmospheric haze.  None whatsoever.  There are also no trees on the moon, nor any roads or buildings (yet).  So those visual cues are also missing.  As a result, an optical illusion comes into play which can make nearby hills almost indistinguishable from far off mountains.

Noticing the size of rocks and boulders might help, but the only way to really recognize the sheer scale of some of these lunar land features (as seen from the lunar surface) is to move around, change perspectives, and try to judge size and distance by parallax.

A few weeks ago, I went planet hunting with my telescope.  Mercury, Venus, and Mars were clustered together in the sky, and I didn’t want to miss that.  I also took a look at the Moon that night.  I’ve seen the Moon in my telescope many times, of course.  I always enjoy looking at the shadows cast by mountains, craters, etc.  But thanks to this new “research crater” I’ve fallen into, that night was the first time I fully appreciated the significance of those shadows.  Those are big shadows.  They must be big shadows in order for me and my relatively small telescope to see them so clearly all the way from Earth.  It takes some stupidly tall mountains and stupidly deep craters to cast such stupidly big shadows across the lunar surface.

WANT TO LEARN MORE?

To make landing on the Moon safer and easier, the Apollo missions mostly stuck to flat terrain regions.  Mostly.  The exception is Apollo 15, which landed near a mountain range called Montes Apenninus.  Click here to learn more about Apollo 15 and the terrain around the Apollo 15 landing site.

Additionally, I found this video from Astrum really helpful in understanding the true size and scale of lunar surface features.  The video also talks about how your eyes can deceive you when viewing the lunar landscape.