IDENTIFYING GEOMORPHIC FEATURES ON VENUS IN THE SAR DATA GORES

Synthetic aperture radar (SAR) data of Venus collected by Magellan was converted into full resolution radar mosaics (FMAPS) after the mission was complete. These FMAPS cover ~92% of Venus, leaving data gores that result in gaps in our knowledge. Geomorphic mapping of Venus utilizing the FMAPS has led to interpretations of what features might be present in the data gores.

We have constructed the geologic map of the V-18 Lachesis Tessera quadrangle (25^o-50^oN, 300^o-330^oE). Like much of Venus, exposures of volcanic materials superpose regional plains throughout V-18. Small shield volcanoes, ~10 km in diameter, are common both in large groups (shield fields), small clusters, or as individuals; associated flow fields are brighter (rougher) than the regional plains. Isolated flows are moderately bright digitate flows that do not have a resolvable construct at their source.

Three central volcanoes are marked by calderas surrounded by digitate flows of variable brightness. Eostre Mons (45.1°N, 329.1°E) is the smallest of the three, at 26 km diameter and ~250 m of relief. Volcano A (28.5^oN, 326.3^oE) is the largest (50 km diameter, 850 m relief) and has the most extensive flows. There is no topography of Volcano B (36^oN, 317.5^oE), but its caldera is 4.7 km in diameter and it has the most distinct associated flow fronts.

Our geologic mapping suggests that there may also be other central volcanoes hiding in the data gore that crosses V-18. A set of graben extend radially from a point within the gore, at 38.2^oN, 322.6^oE. Dark (smooth) digitate flows extend away in all directions from this point, partially covered by several younger, brighter (rougher) flows. Altimetry coverage of the data gore reveals a 112 km diameter topographically-high ring feature at the radiating point of the linear structures. We interpret this as a caldera and map the feature as Volcano C; this putative volcano has at least 1 km of relief.

Similarly, a set of linear structures extend radially from another point in the data gore (46.8^oN, 321.5^oE) where topography shows a ring feature. While this feature does not have any obvious associated flow fronts, it is possible that it too is a central volcano.

New global SAR data will be acquired by the upcoming VERITAS mission. These data will fill in the data gaps and allow us to confirm if these features are indeed volcanoes.