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I'm curious about how mountains on an airless world such as the Moon would look if you were standing on the surface and looking at them. There are plenty of artists' impressions, of course, but I'm curious about whether there are any existing photographs of such a scene.

From browsing photographs of the Moon landings, there are a few surprisingly rounded-looking low hills on the horizon, but not what you'd call an actual mountain. This makes sense, since the missions targeted large flat areas where it would be safe to land. There are photographs of mountains seen from Lunar orbit, but not from the surface.

There are photographs of Mount Sharp from the Curiosity mission to Mars, but Mars has an atmosphere, and to my untrained eye Mount Sharp looks quite eroded.

So I'm wondering whether there are any such photos in existence at all - either because a probe has landed on an airless body close enough to a mountain to get a picture, or because a camera in orbit has been aimed at the horizon in order to capture a mountain range from the same angle at which it would be seen from the surface.

Alternatively, are there any mountains on Earth where (for whatever reason) erosion hasn't played a big role in shaping them so far, and which therefore look similar to the uneroded mountains one would find on an airless world?

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    $\begingroup$ Some of those "rolling hills" you see on the horizon in Apollo photographs are mountains taller than the Alps. $\endgroup$ – David Hammen Jun 15 '14 at 10:37
  • $\begingroup$ Maybe look at some of the Icelandic mountains? They're pretty new in geological timescales, and I remember thinking "wow, these look sharp, pointy and uneroded" from the back of a snowmobile :-) IANA geologist, though, so I may have misread things. $\endgroup$ – Semidiurnal Simon Jun 16 '14 at 5:31
  • $\begingroup$ Because there is no air on the Moon, some of the visual cues (such as haze) people use to judge distance (and estimate height) don't work. Plus your eyes are fooled by the closer horizon. So the mountains in the Moon photographs look closer and smaller than they really are. $\endgroup$ – Spencer Sep 30 '16 at 22:54
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    $\begingroup$ Camilo Rada says that mountains poking above the Antarctic icefields can have very little erosion. $\endgroup$ – Keith McClary Apr 13 '19 at 3:06
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Here's how astronomers of the late 19th century thought the Moon would appear:


Recreations in Astronomy by H. D. Warren D. D., published in 1879, via http://en.wikipedia.org/wiki/Selenography.

Here's what Apollo 15 astronauts saw:

Apollo 15 Lunar Module Falcon at the Hadley-Apennine landing site. Hadley Delta in the background rises approximately 4,000 meters (about 13,124 feet) above the plain. The base of the mountain is approximately 5 kilometers (about 3 statute miles) away.

Source: NASA, from Four Out of Six Apollos.

Below is a photograph of the even taller Mons Hadley, 1.1 km taller than Hadley Delta shown above:

Source: NASA, photograph as15-86-11603, from Apollo Imagery.

Compare the above with mountains on the Earth. Here's a picture of Mont Blanc, a mountain here on the Earth comparable in size to the smaller of the two lunar mountains portrayed above:

Photograph by Zoharby, taken from Wikimedia Commons, licensed under Creative Commons Attribution-ShareAlike 3.0 Unported license.


Alternatively, are there any mountains on Earth where (for whatever reason) erosion hasn't played a big role in shaping them so far, and which therefore look similar to the uneroded mountains one would find on an airless world?

Nathaniel, you have a mistaken view of erosion. Erosion eventually does tear the tallest mountains down to tiny little hills. However, erosion also makes those tall mountains very jagged at first. Erosion is the primary reason why Mont Blanc and other new, tall mountains are so jagged. Liquid water seeps into cracks in the rocks and then freezes into ice. Ice has a lower density than water. This means that liquid water expands upon freezing. That expansion breaks the rock that form mountains into jagged edges.

Another reason our mountains are jagged is plate tectonics. The Earth is the only body in the solar system that exhibits plate tectonics. New continental crust forms largely from older continental crust. Erosion eventually brings particles torn from mountains to a flat area or river delta, where they collect. The material brought to those collection areas changes over time. The end result: Strata (layered rock formations). The different strata in rock have different strengths and weaknesses and thus erode differently. That differential erosion results in jagged mountains.


Bottom line: You don't see jagged mountains on the Moon or Mars because they don't have water in all three phases and because they don't have plate tectonics.

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  • $\begingroup$ That looks very different from the Mont Blanc I know... $\endgroup$ – gerrit♦ Jun 15 '14 at 13:19
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    $\begingroup$ @gerrit - Which Mont Blanc do you know? This one, from the France side? Or perhaps this animated gif created by NASA? I chose the image I used because it's so nice and jagged looking. I chose it over the panoramic view from the France side because that latter view isn't quite so jagged, and I choose it over the animated gif because I am very much not a fan of animated gifs. $\endgroup$ – David Hammen Jun 15 '14 at 13:35
  • $\begingroup$ Two more that are very nice: sweclimber.files.wordpress.com/2011/07/… and science.nationalgeographic.com/wallpaper/science/photos/…. However, I'm leery of those because of potential copyright issues. The first three images I used are public domain. The Mont Blanc photo I used is not public domain, but the copyright owner does allow unrestricted usage so long as the user provides proper attribution. $\endgroup$ – David Hammen Jun 15 '14 at 13:44
  • $\begingroup$ Yes, I know the one from the French side :). The Mont Blanc massif is huge though, I wonder if people sometimes use the word Mont Blanc for other peaks in the same massif, such as Mont Blanc du Courmayeur, Mont Blanc du Tacul, etc. I thought the summit of the actual Mont Blanc was rather flat and "boring", but perhaps I'm wrong. $\endgroup$ – gerrit♦ Jun 15 '14 at 18:44
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    $\begingroup$ I don't think your "bottom line" is quite right. Mars does have jagged mountains. The moon has smooth mountains that look like rolling hills because the erosion experienced on the moon is caused by micrometeorites and there's no wind or water to transport the resulting regolith away. This means that ejecta slowly migrates downhill (diffusive transport). $\endgroup$ – equant Jun 18 '14 at 5:10
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After I asked the question, the Rosetta mission sent back some glorious images of rocks as jagged as those on any science fiction book cover:

enter image description here

I suppose the difference is that these are on the surface of a comet, which, unlike the Moon, is geologically active.

These are hardly what you'd call mountains - the whole nucleus is only 4km long, so the features shown must be hundreds of metres in size at best. But still, I would imagine freshly formed mountains would look something like this in the absence of erosion.

It never rains but it pours. Here is a glorious photo of mountains on Pluto from NASA's New Horizons mission, from September 2015. Pluto is another (surprisingly) geologically active world, with apparently little erosion. These ones really are mountains, about three kilometres in height. They are probably made of water ice rather than rock, which is very hard at those temperatures. They also apprear very jagged.

enter image description here

I conclude from this that mountains on active worlds without erosion will generally appear jagged; the smoothness of the Moon's mountains is not due to the absence of erosion - rather, they're smoothed because of erosion, which in the Moon's case is primarily due to micrometeorites and takes place over a very long time. This is possible because the Moon is not geologically active, so its mountains are far older than the ones in the pictures above.

Finally, I can't resist editing again to add another image from the Rosetta mission, taking during the spacecraft's final descent before a controlled collision with the comet in September 2016. It's just an incredibly beautiful image. (source)

enter image description here

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    $\begingroup$ The comet is "geologically active", but not in the sense that you think it is. It is just a collection of random rocks, dust and ice which are held together by gravity. The gravity was not strong enough to turn the entire thing into a sphere (like Earth, the Moon and Mars) so the "jaggedness" remains. No new "jaggedness" is forming there over geological type, unlike on Earth. $\endgroup$ – Gimelist Dec 7 '14 at 7:41
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    $\begingroup$ @Michael that may or may not be true. It's an active comet, and substantial amounts of material are ejected every time it passes near the Sun. You can see the beginning of this in some of the photos. (It is currently just beginning a flyby of the Sun.) Rosetta will continue to orbit it as it passes by the Sun, and then we'll see if this has any effect on the surface features. $\endgroup$ – Nathaniel Dec 7 '14 at 9:10
  • $\begingroup$ True. Point taken. $\endgroup$ – Gimelist Dec 7 '14 at 9:15
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    $\begingroup$ In 2015 (after these comments) Rosetta identified a fresh landslide: phys.org/news/… $\endgroup$ – sdenham Aug 7 '17 at 1:38
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I'd like to add to David's excellent answer.

Your premise is that there are "mountains before erosion" is not exactly accurate. Mountains, in the sense that think of them (local elevated regions above their surroundings, e.g. Mont Blanc) form because of erosion. In that case, mountains without erosion would simply not be mountains. Note that there can be two kinds of erosion: physical weathering and chemical weathering. A bit more about it in https://earthscience.stackexchange.com/a/2306/725

Let's take at look some examples:

The Tibetan plateau is elevated because of the collision of two continental lithospheric plates. If you look at the topography, you will see that areas that are not nearby any serious elevation differences are not that jagged, for example in the center north area.

An example from the Grand Canyon. Looking down from the Colorado river, I'm pretty sure that you will agree the it's a mountain, and a jagged one. But other than that, there is nothing. It's a flat plateau. The Colorado plateau is very high in elevation, but without erosion it simply doesn't look like a mountain at all.

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  • $\begingroup$ Your first example seems to disprove your point. "The Tibetan plateau is elevated because of the collision of two continental lithospheric plates" - i.e. not because of erosion. Your second example is confusing. Sure, in this case, the jaggedness of the sides is due to erosion caused by the river - but then so is the flatness of the plane above them, isn't it? So I'm not sure what it shows - erosion can cause jagged mountainsides, but then so can other things, and the question was about mountains caused by other things, in the absence of erosion. $\endgroup$ – Nathaniel Dec 7 '14 at 9:06
  • $\begingroup$ 1st point: Exactly! That's why the Tibetan plateau is not all mountains. Again, if you look on the north area, it's quite flat relatively to the southern area (the Himalaya). 2nd point: That flatness of the plain was not caused by the river. Rivers do not flatten things, they do the opposite. The thing is that mountains, almost by definition, at least on Earth, are the result of erosion. Otherwise, they wouldn't be mountains. Just elevated plateaus. This is excluding volcanoes of course, which is another story. $\endgroup$ – Gimelist Dec 7 '14 at 9:15
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Fresh shield volcanoes that are dome-shaped may be of interest to you.

enter image description here

Shield volcanoes on Venus - The Pancake Domes
enter image description here

Shield volcanoes on Earth - The Galapagos Islands enter image description here

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It's a question of rates of erosion. All mountains start to erode from the moment that mountain building begins. The erosion stops, or slows down to minuscule amounts when the mountains are protected by a vast thickness of ice, as in Greenland and the Antarctic. As soon as the ice starts to melt, normal rates of erosion will resume. Rates of erosion on extraterrestrial surfaces are usually much slower than on Earth, and of different kinds. Mechanisms include thermal expansion and contraction, wind ablation (if there is any kind of atmosphere), melting, micrometeorite to bolide impacts, rock tides, and differential gravitational effects. No part of the cosmos is totally immune from erosion.

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Alternatively, are there any mountains on Earth where (for whatever reason) erosion hasn't played a big role in shaping them so far, and which therefore look similar to the uneroded mountains one would find on an airless world?

The entire Tibetan plateau is a mountain range unexposed to erosion. It's a lifted landmass that just needs a little rain and snow to get the ball rolling. Same goes for the Colorado plateau, although in a few small sections, moisture has carved a few canyons and valleys that may end up as mountains.

There is essentially no difference, visually, between a flat plain and an uneroded mountain range.

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