Microwave Signatures and Surface Properties of Ovda Regio and Surroundings, Venus

Arvidson, R. E.; Brackett, R. A.; Shepard, Michael K.; Izenberg, N. R.; Fegley, B.; Plaut, J. J.

doi:10.1006/icar.1994.1176

Cited by 26 publications

(24 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Most of the landforms at Venus's surface are typical of low‐viscosity basaltic volcanic rocks: broad flat plains, fields of small shield volcanoes, and immense central shield volcanoes (Ivanov & Head, ). Rare volcanic domes (such as the “pancake domes”) may have formed from silica‐rich lavas (Fink et al, ), but they may also have formed from crystal‐rich basaltic lavas (Arvidson et al, ; Fink & Griffiths, ; Sakimoto & Zuber, ; Stofan et al, ). The presence of abundant granitic rocks on Venus, though, would have immense consequences for understanding its past: production of large volumes of granitic igneous rocks requires abundant water (Campbell & Taylor, ), which would imply that Venus once had enough water to have potentially habitable environments (Way et al, ).…”

Section: Introductionmentioning

confidence: 99%

Ovda Fluctus, the Festoon Lava Flow on Ovda Regio, Venus: Not Silica‐Rich

et al. 2019

View full text Add to dashboard Cite

Ovda Fluctus (6.1°S, 95.5°E) is a lava flow complex on the equatorial tessera highlands of Ovda Regio, Venus. We examined its morphology and geologic setting to determine if its apparent emplacement rheology is consistent with silica‐rich (e.g., rhyolitic) lava; this has significant implications for the compositions of Venus's tesserae. Using Magellan radar data, we find that the radar properties (emissivity, roughness, and backscatter) of Ovda Fluctus are similar to those of the surrounding tessera, although the flow is smoother at multiple scales. Ovda Fluctus is a “festoon flow complex,” whose surface is rumpled into arcuate folds. The flow includes multiple flow lobes and at least two distinct flow units. The flow complex includes a portion at high altitude (~5 km above mean planetary radius) that has low radar backscatter and high radar emissivity compared with lower‐altitude portions of the complex. The high‐altitude region of Ovda Fluctus is continuous with the lower‐elevation portions: the change in radar properties does not represent different flows. Outlines of Ovda Fluctus flow lobes have fractal dimensions consistent with basaltic pahoehoe lavas. The margin of Ovda Fluctus is at significantly higher elevation than its center, a characteristic seen in basalt flows on Earth, but not on more silica‐rich flows. Thus, the available evidence suggests that Ovda Fluctus had an emplacement rheology consistent with a basaltic composition; this result provides no support for hypotheses that Ovda Regio (a highlands tessera terrain) is composed of granitic rock.

show abstract

Section: Introductionmentioning

confidence: 99%

Ovda Fluctus, the Festoon Lava Flow on Ovda Regio, Venus: Not Silica‐Rich

et al. 2019

View full text Add to dashboard Cite

show abstract

“…The major concern is ''masking'' of the tessera surface composition by ejecta from basaltic plains regions (e.g., Basilevsky et al, 2004), but even craters in the tesserae may create debris that is significantly altered from the original target material. Similar concerns arise for regions at elevations (about 6053 km planetary radius for equatorial sites, increasing to 6055 km at high latitudes) where high-dielectric precipitates are known to occur from anomalously low microwave emissivity values Arvidson et al, 1994;Campbell et al, 1999). Requiring polarimetric radar coverage, at present, limits the geographic range to those regions visible from Earth near inferior conjunction.…”

Section: Discussion and Implications For Future Explorationmentioning

confidence: 99%

“…Definitive answers regarding tessera composition will require more detailed remote sensing or a landed mission (Basilevsky et al, 2007; Report of the Venus Science and Technology Definition Team, 2009). Our knowledge, however, of weathering and other physical processes operating in the tesserae (Campbell et al, 1999;Arvidson et al, 1994;Head, 1988, 1989), and how the visible surface has been modified by crater ejecta Garvin, 1990), remains very limited. The latter topic is of particular importance given the unique nature of distal impact crater deposits on Venus.…”

Section: Introductionmentioning

confidence: 99%

Evidence for crater ejecta on Venus tessera terrain from Earth-based radar images

Campbell

Morgan

et al. 2015

Icarus

View full text Add to dashboard Cite

a b s t r a c tWe combine Earth-based radar maps of Venus from the 1988 and 2012 inferior conjunctions, which had similar viewing geometries. Processing of both datasets with better image focusing and co-registration techniques, and summing over multiple looks, yields maps with 1-2 km spatial resolution and improved signal to noise ratio, especially in the weaker same-sense circular (SC) polarization. The SC maps are unique to Earth-based observations, and offer a different view of surface properties from orbital mapping using same-sense linear (HH or VV) polarization. Highland or tessera terrains on Venus, which may retain a record of crustal differentiation and processes occurring prior to the loss of water, are of great interest for future spacecraft landings. The Earth-based radar images reveal multiple examples of tessera mantling by impact ''parabolas'' or ''haloes'', and can extend mapping of locally thick material from Magellan data by revealing thinner deposits over much larger areas. Of particular interest is an ejecta deposit from Stuart crater that we infer to mantle much of eastern Alpha Regio. Some radar-dark tessera occurrences may indicate sediments that are trapped for longer periods than in the plains. We suggest that such radar information is important for interpretation of orbital infrared data and selection of future tessera landing sites.Published by Elsevier Inc.

show abstract

“…Choudhury et al (1979) and volume scattering can be important factors, and careful modeling is required (e.g. Arvidson et al, 1994) to detect a thermal anomaly in a single observation (repeat-pass change detection is of course more straightforward) (see Fig. 1).…”

Section: Thermal Evolution and Microwave Remote Sensingmentioning

confidence: 99%