ANISOTROPY DETECTION SOFTWARE: INITIAL RESULTS ON VENUS

We have developed software to facilitate detection of anisotropy in the distribution of point-like features. Using the methodology of Lutz [1986] and Cebriá et al. [2011], the software allows the user to enter a table of x,y coordinates and output azimuth histograms. Both whole-field and local-scale alignments can be examined [Thomson and Lang, 2016]. A built-in Monte Carlo model tests the observed distribution of alignments against a family of randomly-generated distributions to help infer the significance of the results. Source code and a pre-bundled MATLAB executable (no license required) are available as supplementary online material to the paper and on the github software repository (github.com/flatline-d/two-point-azimuth-gui).

One area where this software can be applied is in the determination of the relative stratigraphic position of shield fields on Venus. For example, some prior studies have reached diametrically opposed conclusions about the age of shield fields relative to nearby regional plains units [Addington, 2001; Ivanov and Head, 2004]. BU graduate Anthony Maue has examine four of these shields fields using the new software: two sites where these prior studies reached opposing conclusions, one site where they agree, and one ambiguous site [Maue et al., 2016; Maue, 2016]. Although the small sample size precludes drawing firm conclusions, the results suggest a range of shield field ages, a finding possibly in line with a “non-directional” model of Venus’ resurfacing history.

References:

Addington, E. A. (2001) Icarus, 149, 16-36.

Ivanov, M. A., and J. W. Head (2004) JGR, 109(E10001), doi:10.1029/2004JE002252.

Cebriá, J. M., et al. (2011) JVGR, 201, 73-82.

Lutz, T. M. (1986) JGR, 91(B1), 421-434.

Maue, A. D., et al. (2016) LPSC, 47, abs. #2805.

Maue, A. D. (2016), Determining local stratigraphy from Venus shield field alignments, B.A. thesis, 55 pp, Boston University.