Ars Geophysica

I’ve spent much of the past little while editing an (extended) abstract, for planned submission to the coming LPSC conference in January. This has been surprisingly difficult – perhaps owing from the fact that I had originally written a 6-page abstract, which needs to be pared down to 2 pages as per the formatting requirements of the conference. Fortunately, I think I’m nearly there – though it’s required a lot of thinking on what is really important, and what is more of a footnote. Most of the methodology concerning the…read more

I) Preamble  I came across a very insightful paper pertaining to 2D surface roughness characterization. Entitled “Characterization of the Structure of River-Bed Gravels Using Two-Dimensional Fractal Analysis” (Butler, Lane, and Chandler 2001), it one way to illustrate 2D roughness and associated anisotropy in such: contour diagrams (logarithmically-spaced), over a specified lag space. Since the method is essentially the same as that which I (mistakenly thought I) came up with, the only steps required are plotting the RMS Deviation (which is the square root of the semivariance employed by Butler) as…read more

I: Preliminaries I’ve been doing further work on classifying the spatial distribution of and relationships amongst the mushrooms in Kings Bowl . In particular, I’m testing the hypothesis of whether there’s a bias in their elevations towards lower elevations – where this bias is with respect to the larger population of elevation values throughout the lava pond at Kings Bowl (approximately coincident with the extent of the circle below). While this may seem qualitatively apparent given the map below, given the apparent clustering of mushrooms in the depressions (purple regions),…read more

Summary of Selected Chapters from “Volcanism of the Eastern Snake River Plain, Idaho: A Comparative Planetary Geology Guidebook” (NASA 1977) _______________________________ Chapter 1: Introduction (Greeley and King) -Basaltic volcanism appear to cover substantial areas of the terrestrial planets -The Snake River Plain (SRP) is similar in morphology to many volcanic regions on the Moon/Mars/Mercury -SRP is an optimal analogue owing to its good preservation state, lack of forests / heavy vegetation (which would impede radar), and good network of jeep trails -Study is restricted to central and Eastern sections of SRP…read more

Previous workers (Catherine Neish, Mike Zanetti) have observed the presence of so-called ‘mushroom’ features at COTM’s Kings Bowl lava field. Also known as pop-ups, one hypothesis, posited by Zanetti, is that the mushrooms are positive topographic anomalies that were created when pyroclasts from the nearby fissure impacted, forming holes in cooled lava through which lava could rise, then cooling into hemispherical, ‘mushroom’-shaped depressions. Here are some pictures by Catherine of the mushrooms in question. Ostensibly, the mushrooms are heterogeneous, with varying levels of symmetry, aspect ratio (eg. height vs. radius),…read more

I: PREAMBLE In my last post, I tried to establish some reasons as to why there were cross-shaped artifacts in the 2D roughness algorithm I had been using. One thought that came to mind after writing that: why should there be a bias towards one point within a local neighbourhood? As Shepard (2003) states, one can implement ‘interleaving’ in order to maximize the information used. Interleaving can be best understood by beginning with a one-dimensional example. For instance, assume that we have a profile 1m long, and wish to measure…read more

Now I’ll move on to some new, fully 2D roughness maps produced by revised roughness algorithms, that fully take into account potential directional bias (which is inherent to 1-dimensional profile methods). Again, we’re looking at our test DEM dataset of Ina D caldera on the Moon. I: Ina D 2D Roughness Maps  Here’s the reference DEM, with which we can see what features the roughness maps emphasize (or do not).   The RMS slope and Hurst exponent are calculated in 2 dimensions (or 3, if height is included) via the…read more

And so it would seem that in no time at all, I’m nearly at the halfway point of my time as an intern at the Neish lab! As befits such an occasion, I’ll be discussing in this post my goals for the remainder of my internship. This will be divided into 2 sections: a ‘summary’ section of broad, overarching goals, and a more comprehensive section containing detailed goals and methods for achieving such. Of the latter, most of these were suggested during discussions with Mike, while a couple are things…read more

Whenever you use a new technique, it’s important to know exactly what it’s doing – otherwise, we’ll be potentially in the dark when it comes to actually interpreting the results of the technique. For the case of my project, I’ve been interested for a while now in implementing Mike Zanetti’s suggestion to apply filtration and roughness calculation methods from the metrology community (as in the study of measurement, not to be confused with meteorology!). On that basis, the Gaussian filter has been for several decades the industry standard – and specifically, the…read more

Just kidding – time isn’t a consideration in our research. Yet. For now, we’ll stick with 3 spatial dimensions. And so our adventures in the wondrous world of surface roughness continue! As illustrated in my last post, during which I showed some maps of the calculated roughness of Ina D Caldera on the Moon, the traditional way to pre-process the topography maps of surfaces and calculating their roughness parameters is to perform ‘de-trending’ for every 1-dimensional profile. In other words, the best-fitting linear trend along a profile (each of which has a length of 100m,…read more