I'm going to be analyzing the Mars Craters dataset (codebook here). Specifically, I'm curious to see if the number of visible layers in a crater varies with the latitude of the crater because I think that'll indicate some interesting things about the makeup of the surface of Mars (like how homogenous - or heterogeneous - it might be).
Mission 1: Determine if there's an association between the number of layers visible and the latitude of the crater.
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| View over the Acidalia Planitia. Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO |
But wait! What if the number of layers is affected by the morphology of the ejecta? (Or vice versa) And what if the ejecta is associated with the latitude? That could mean that the number of visible layers doesn't depend on the makeup of the surface but instead depends on the morphology of the ejecta. And maybe the ejecta morphology was determined by how the group of particular meteors slammed into the surface so many millions of years ago. Of course, this is all just speculation right now but that led me to my second topic:
Mission 2: Determine if there's an association between the number of layers visible and the morphology of the ejecta.
Bonus Mission: Determine if there's an association between the ejecta morphology and the latitude.
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| Another view of the Acidalia Planitia because it's just so pretty. Credit: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO |
Literature Review
Searching on Google Scholar for "Mars craters morphology and latitude" yielded the following results:
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| Look at that first result. Beautiful. |
The literature reveals that there's a known correlation between latitude and crater depth (due to ice) and that "the latitudinal variations seen for rampart crater morphologies correlate well with the proposed latitude-depth relationship for ice and brines across the planet." [1] However, it was also pointed out that certain morphologies of the ejecta seemed to be related more to the impact energy rather than the makeup of the surface. [1] Another paper argues that other morphologies are strongly related to the latitude (and altitude) of the crater. However, the authors used data from craters that are more recent than the ones found in the dataset I'll be using. [2] A third paper also confirms that there's a correlation between crater depth and latitude but doesn't relate it to the crater or ejecta morphology. [3]
From the papers, it's clear that there's a correlation between latitude and crater depth and that it's likely due to ice. There's also a correlation between some ejecta morphologies and latitude while other morphologies are more closely related to impact energies rather than latitude.
Because there's already a known correlation between the ejecta morphology and the latitude, my bonus mission has already been accomplished (just not by me). However, my other two missions are still intact.
The literature above did not indicate if there's a previously known association between the ejecta morphology and the number of layers (Mission 2) so there may or may not be. And so I went on a hunt for more literature. After searching for "Mars Craters latitude and layers," I found a paper that stated: "Single-layer ejecta (SLE) morphology is most consistent with impact into an ice-rich target. Double-layer ejecta (DLE) and multiple-layer ejecta (MLE) craters also likely form in volatile-rich materials, but the interaction of the ejecta curtain and target-produced vapor with the thin Martian atmosphere may be responsible for the large runout distances of these ejecta."[4]
The fourth article specifically looked at craters in the northern hemisphere but, because there's a link between layers and the makeup of the ground (i.e. whether there's ice or not) - which was also found between morphology and latitude - it's likely that there's a good chance that there's an association between latitude and the number of layers in a crater. And, if that association exists, there will likely be an association between layers and latitude (Mission 1). Also, if there's a relationship between crater depth and number of visible layers, then it's probable that there will be an association between layers and latitude (since depth and latitude show a correlation). Oh! Which gives me an idea:
New Bonus Mission: Determine if there's an association between the number of visible layers and crater depth.
So, to recap:
| Mission | Description | Variables | Hypothesis |
|---|---|---|---|
| 1 | Determine if there's an association between the number of layers visible and the latitude of the crater. | NUMBER_LAYERS and LATITUDE_CIRCLE_IMAGE | Weak association |
| 2 | Determine if there's an association between the number of layers visible and the morphology of the ejecta | NUMBER_LAYERS and MORPHOLOGY_EJECTA_1 | Association |
| Known correlation for certain morphologies and known lack of association for other morphologies | |||
| New Bonus | Determine if there's an association between the number of visible layers and crater depth. | NUMBER_LAYERS and DEPTH_RIMFLOOR_TOPOG | Association |
Glossary
Ejecta - particles that were forcefully moved from an area. In this case, the ejecta is the material that was thrown out of the crater when the meteor struck the surface. The ejecta settles back onto the surface of the planet after the initial impact.
Morphology - the structure of something. In this particular dataset, the morphology refers to the shapes and structures of the craters and/or their ejecta.
Sources
[1] Barlow, Nadine G., and Tracy L. Bradley. "Martian impact craters: Correlations of ejecta and interior morphologies with diameter, latitude, and terrain." Icarus 87.1 (1990): 156-179.
[2] Mouginis‐Mark, Peter. "Martian fluidized crater morphology: Variations with crater size, latitude, altitude, and target material." Journal of Geophysical Research: Solid Earth (1978–2012) 84.B14 (1979): 8011-8022.
[3] Robbins, S.J. (2011) "Planetary Surface Properties, Cratering Physics, and the Volcanic History of Mars from a New Global Martian Crater Database" Ph.D. Thesis, University of Colorado at Boulder.
[4] Barlow, Nadine G. "Impact craters in the northern hemisphere of Mars: Layered ejecta and central pit characteristics." Meteoritics & Planetary Science 41.10 (2006): 1425-1436.
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