Jargons like geology, geophysics, geothermal has its origin in and has strong connections with Earth.

Other jargons like the closet point and farthest point of an orbit to a heavenly body get specific names(say perigee & apogee for earth orbit, Periareon & Apoareon for Martian orbit).

So, it is acceptable to use terms like geology, geophysics for Martian context? Are there planet specific terms? Or will introducing such very specific terms lead to an undesirable overflow of jargons?

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    $\begingroup$ In planetary science, "geology" refers to the study of the solid parts of any planet or moon. You don't change the word based on which body you're looking at. $\endgroup$ Nov 27, 2018 at 6:58
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    $\begingroup$ As The Oracle said to Neo: "What’s really going to bake your noodle later on is would you still have said "Geology" if I'd asked about Jupiter" $\endgroup$
    – uhoh
    Nov 27, 2018 at 11:27
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    $\begingroup$ I've often heard the "exo-" prefix is applied when talking about places other than Earth such as "exogeology" or "exobiology" but I'm not sure if this is an official designation. $\endgroup$
    – Dragongeek
    Nov 27, 2018 at 14:47
  • $\begingroup$ Areology? I think practically speaking, people will just say "Martian geology". $\endgroup$ Feb 23, 2019 at 4:41

3 Answers 3


The words perigee and apogee (and their planet-specific equivalents) show it's impractical to use planet-specific names for everything. The solar system alone has far too many objects to make this practical. Try finding a specific word for 'the apoapsis of 67P-Churiymov-Cherasimenko' for instance.

Geology has a sub-field called planetary geology dedicated to the study of the geology of bodies other than Earth. Introductory texts on planetary geology make no reference to planet-specific names. So by all means use 'geology' to describe the solid parts of any astronomical object. See e.g. the Geology of Mars page on Wikipedia.

This is logical: the behavior of soil and rock does not fundamentally change when you go to another planet. You just change some of the variables (gravity, temperature) that dictate behavior.


We're living on a planet whose name (in most languages, including both English and ancient Greek) is synonymous with "dirt", "rock" or "soil". Which, of course, is quite reasonable and descriptive, but it's bound to introduce some ambiguity in those rare instances when we're actually talking about the soil of another big ball of rock.

Anyway, the point is that, on both etymological and practical grounds, the word "geology" can be reasonably interpreted either as "study of the planet Earth" or simply as "study of the ground". In most practical contexts, both in the past, the present and the near future, those are effectively the same thing anyway. It's only in edge cases like "Martian geology" that one interpretation makes more sense than the other.

In fact, even without considering other planets, there is an argument to be made for favoring the "study of ground" interpretation: traditionally, study of the Earth's atmosphere, hydrosphere and biosphere are not considered to be within the domain of geology, even though all those things are also part of the planet. Of course, being part of the same planet, they do interact, and so a geologist might indeed care quite a lot about, say, wind erosion or lake sedimentation or coral reefs, but only insofar as those affect their main subject of study, i.e. the ground.

So, given that Mars is also a rocky planet like the Earth with a similar (though, also, in many important and interesting ways different) lithosphere, I would say that "Martian geology" is a perfectly reasonable name for its study. Especially so since the methods and principles involved in studying it are very much the same as here on Earth, and the results are likely to shed light on the internal structure and history of both planets.


For some especially familiar bodies words specific to those bodies are used, as in "selenonogy" for the study of the Moon. But when we are seeking to emphasize comparability with processes on Earth, then "geology" comes to the fore. For example, when the Moon shows evidence of recent tectonic motion like the Earth has, it is called "geological activity".


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