Mars Crater Database developed by Stuart Robbins

Selected Dataset For this assignment, I have selected the Mars Crater Database developed by Stuart Robbins.

This dataset contains a large-scale global inventory of Mars craters, including variables such as:

Latitude and longitude of crater location Diameter and depth measurements Ejecta morphology classifications Number of identifiable crater layers The dataset is statistically complete for craters with diameter ≥ 1 km, making it suitable for quantitative analysis. [Mars Crater Codebook | PDF]

Topic of Interest (Step 2) My primary topic of interest is:

➡️ Crater size and structure

Specifically:

Crater diameter (DIAM_CIRCLE_IMAGE) Crater depth (DEPTH_RIMFLOOR_TOPOG) These variables describe the physical geometry of craters and provide insight into crater formation processes.

Initial Research Question + Hypothesis ✅ Research Question: Is crater diameter associated with crater depth on Mars?

✅ Hypothesis: Larger craters are expected to have greater depths, but the relationship may not be strictly linear due to erosion, geological modification, and collapse processes.

Personal Codebook (Step 3) Variable Name

Description

Units

CRATER_ID

Unique crater identifier

N/A

LATITUDE_CIRCLE_IMAGE

Latitude of crater centre

Degrees

LONGITUDE_CIRCLE_IMAGE

Longitude of crater centre

Degrees

DIAM_CIRCLE_IMAGE

Diameter of crater

km

DEPTH_RIMFLOOR_TOPOG

Depth from rim to floor

km

All variables are directly defined in the codebook you provided. [Mars Crater Codebook | PDF]

Second Topic of Interest (Step 4) After reviewing the dataset further, I identified a second topic:

➡️ Crater morphology and layering structure

Relevant variables:

MORPHOLOGY_EJECTA_1 / 2 / 3 NUMBER_LAYERS These describe:

Ejecta patterns (e.g., lobes, textures) Structural layering around craters

Expanded Research Question Is crater size (diameter) associated with the number of ejecta layers observed?

Updated Hypothesis Larger craters are more likely to have multiple ejecta layers due to higher impact energy and more complex material displacement.

Updated Personal Codebook (Step 5) Variable Name

Description

Units

DIAM_CIRCLE_IMAGE

Diameter of crater

km

DEPTH_RIMFLOOR_TOPOG

Crater depth

km

MORPHOLOGY_EJECTA_1

Ejecta type classification

Categorical

MORPHOLOGY_EJECTA_2

Ejecta morphology structure

Categorical

MORPHOLOGY_EJECTA_3

Texture/shape classification

Categorical

NUMBER_LAYERS

Number of ejecta layers

Count

Literature Review (Step 6) ✅ Search Terms Used: “Mars crater diameter and depth relationship” “impact crater morphology Mars layers ejecta” “crater scaling laws planetary surfaces” ✅ Key References: Robbins, S.J. (2011). Planetary Surface Properties, Cratering Physics, and the Volcanic History of Mars Melosh, H.J. (1989). Impact Cratering: A Geologic Process Pike, R.J. (1974). “Depth/Diameter relations of Mars craters” Boyce, J. (2008). The Craters of Mars

Summary of Findings (Step 6 – Required) From the literature:

Crater depth increases with diameter, but not proportionally (non-linear scaling). Larger craters often undergo collapse, reducing depth relative to size. Complex craters exhibit: Central peaks Multiple ejecta layers Ejecta morphology depends on: Impact energy Surface composition (ice, dust, rock) Overall pattern: ➡️ Size influences both depth and morphological complexity

✅ Final Hypothesis (Step 7) There is a positive relationship between crater diameter and crater depth, and larger craters are associated with a higher number of ejecta layers due to increased impact energy and structural complexity.