16th VEXAG Meeting 2018 (LPI Contrib. No. 2137) 8046.pdf Venus’ Ishtar Terra: Topographic Analysis of Maxwell, Freyja, Akna and Danu Montes. Sara Rastegar1 and 2 1 ​ Donna M. Jurdy ,​ C​ ity Colleges of Chicago, Harold Washington College, 30 E. Lake Street, Chicago, IL 60601, ​ ​ 2 [email protected], D​ epartment of Earth and Planetary Sciences, Northwestern University, 2145 Sheridan ​ ​ Rd, Evanston, IL 60208, [email protected] ​ Introduction: Venus’ mountain chains (Figure 1) Analysis: We attempt to address these questions ​ ​ ​ surround Lakshmi Planum, a 3-4 km highland, making with analysis of Magellan topographic data for up Ishtar Terra. No other mountain belts exist on quantitative comparison of Venus' four mountain Venus. Circling Ishtar Terra, Maxwell Montes, ascends chains: Maxwell, Freyja, Akna and Danu. Patterns in to over 11 km, ranking as the location of highest topography may provide clues to the dynamics forming elevation on the planet. Freyja Montes rises to over 7 these Venusian orogenic belts. From topographic km, higher than Akna Montes at about an elevation of profiles across the ec mountain chain, we then 6 km. Danu Montes, ~1.5 km over Lakshmi Planum, determine an average profile for each mountain belt. alone displays a distinctly arcuate form. Next, we correlate these averages to establish a measure of similarity between the chains and terrestrial Tectonic Enigma: The existence of the four analogs. These correlations allow construction of a venusian mountain chains has been attributed to covariance matrix, which can be diagonalized for localized downwelling - analogous to terrestrial eigenvalues, for Principal Component Analysis (PCA) subduction - in response to the proposed upwelling [4]. beneath Lakshmi Planum [1,2]. If so, why the asymmetry in the location of the mountain chains, the Summary: PCA allows an independent and objective ​ differences in their elevation and structural mode of comparison of the venusian mountains with topography? Regional E-W shortening (compression), terrestrial counterparts with known tectonic origins. surrounding the planum may have subsequently Comparison can be made with other topographic modified Maxwell and Freyja Montes, as evidenced by features on Venus, such as the chasmata. the folds and faults [3]. References: [1] W. M. Kaula et. al. (1992) JGR: Planets, ​ ​ V.97, 085-120 [2] R. E. Grimm and R. J. Phillips, (1991) Figure 1; Topographic Map of the Ishtar Terra Region ​ JGR: Solid Earth, V. 96, 05-24 [3] V. Ansan et. al. (1994) of Venus, USGS, V 1OM 9O/O RTK, 1998 ​ Planetary and Space Sci., V. 42, 239-261 [4] P. R. Stoddard and D. M. Jurdy, (2011) Icarus, V.217, 524–533 ​.