Back-Projecting Secondary Martian Craters Using a Cone of Uncertainty GEOG 596A Proposal, Spring 2 2017 Tim Naegeli

Agenda Background Objectives Study Areas Data & Software Workflow Anticipated Results

Background In absence of samples, cratering is the only way to determine the age of a surface

Background Laura, J., Skinner Jr, J.A., and Hunter, M.A. (2017) Large Crater Clustering Tool. Computers and Geosciences (submission).

Characteristics of Secondary Craters Background Characteristics of Secondary Craters Pattern Size Depth Shape

Background

Background

Background

Objectives The purpose of this project is to determine an effective method to back-project secondary craters on Mars to determine the primary crater that created them.

Study Areas

Study Areas Zunil 10.1 kilometer diameter Primary crater Secondaries occurring in obvious rays “Control” for the project

Study Areas Lyot 222 kilometer diameter Primary crater Older area than Zunil, no obvious rays Robbins and Hynek (2011) identified secondaries up to 5,200 kilometers away from Lyot

Study Areas Bonneville 210 meter diameter Visited by Spirit in 2004 Like a secondary due to size and depth Unknown primary source

Software & Data ArcMap THEMIS CTX HiRISE Mars Odyssey 100m IR, 18m VIS spatial resolution 2002 – Today Planet wide coverage CTX Mars Reconnaissance Orbiter 8 m spatial resolution 2006 – Today “Regional” coverage HiRISE 25 cm spatial resolution “Local” coverage

Workflow

Workflow

Workflow Crater characteristics are captured… …then categorized Diameter Ellipticity (1 – Dminor/Dmajor)

Workflow

Workflow See how many line back-projections intersected with Zunil By diameter and ellipticity See how many cone back-projections intersected with Zunil Compare line and cone results At what cone size do the amount of intersections significantly improve (for each diameter and ellipticity) Record “final” back-projection parameters

Workflow Part 2 – Lyot Part 3 – Bonneville Process is essentially the same as Zunil, except start with the information learned at Zunil Only go through combinations again if no progress shown Part 3 – Bonneville Digitize Bonneville Create 3,000 km buffer Digitize all craters with 20x Bonneville’s diameter Find intersection(s) Identify most likely source

Anticipated Results Cone of uncertainty offers significant improvement over line Each crater system and type will present new challenges, but generally there should be a way to identify the cone More work needed Other systems Potential multiple sources?

Thank you!