Polygonal Plains on Venus Linked to Global Climate Change TALKING POINTS FOLLOW FROM THIS POINT

Polygonal Plains on Venus Linked to Global Climate Change TALKING POINTS FOLLOW FROM THIS POINT www.phwiki.com

Polygonal Plains on Venus Linked to Global Climate Change TALKING POINTS FOLLOW FROM THIS POINT

Esler, David, Contributing Editor has reference to this Academic Journal, PHwiki organized this Journal Solar System Exploration: Space Science Highlight Featuring the Research of Suzanne E. Smrekar, Pierre Moreels, in addition to Brenda J. Franklin To be published in the Journal of Geophysical Research: JGR Planets Characterization in addition to Formation of Polygonal Fractures on Venus Contact: Suzanne.E.Smrekar@jpl.nasa.gov Polygonal Plains on Venus Linked to Global Climate Change Greenhouse effects of global warming occur on both planets. Interplay between the atmosphere in addition to lithosphere can stabilize-or destabilize- global climate change over multimillion year time scales What can we learn about Earth by exploring Venus Planetary Scientists are exploring Venus today By examining radar image mapping sent back by NASA’s Magellan Mission nearly a decade ago Polygons average ~2 km across. Are polygons stratigraphic markers What play of as long as ces best explains the magnitude in addition to uni as long as mity of polygon size at over 200 sites Global Climate Change Model Fits Best! Solving the Mystery of the Polygons of Venus

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Polygons as long as med from cooling of volcanic lava flow Diameter measured in meters Did Giants as long as m these polygons on Earth Giant’s Causeway Irel in addition to http://www.giantscausewayofficialguide.com Volcanism Subsurface Heating Global Climate Change Evidence: Uni as long as m size ~ 2km across Global distribution ~ 200 sites Fits Global Climate Change Model Venusian Polygons What titanic as long as ces caused them to as long as m 82 km Example of gradation in size from large to small. Polygons in this region range from 6 km near top to 1 km near bottom. (Fmap 35S253, Figure 1 in Smrekar et. al. JGR-Planets, to be published.) Venusian polygons have average diameter of 1.8 ± 0.9 km Several orders of magnitude larger than on Earth

Global Distribution of Polygons on Venus Model validated by new study: Anderson in addition to Smrekar (1999) proposed Global Climate Change Model as mechanism of as long as mation of polygonal terrain: global warming following by gradual cooling produces sufficient thermal stresses to produce strains on surface in addition to observed fracture spacing. SIGNIFICANT RESULTS Polygonal fractures on Venus indicate Global Climate Change process Tectonic Effects of Global Climate Change on Venus Time0 ~ 750 Million years ago Rapid Cooling Causes Contraction To depth: of ~20 km TALKING POINTS FOLLOW FROM THIS POINT

Venus Polygons How did they as long as m THREE Proposed as long as mation mechanisms Volcanism: Cooling following lava flow emplacement Why Polygons typically found on surface of slowly cooled lava flows Why NOT To obtain large size, would need to be a lava flow 20 km thick Lithospheric heating Why Local heating events consistent with lithospheric cooling Why NOT Inconsistent with variable size in addition to pattern of diminishing size moving away from center of heating Global Climate Change Anderson in addition to Smrekar (1999) propose Global Climate Change Model as mechanism of as long as mation of polygonal terrain: global warming following by gradual cooling produces sufficient thermal stresses to produce strains on surface in addition to the observed fracture spacing. Builds on work of Bullock in addition to Grinspoon (1996, 2001): Resurfacing event ~750 M years ago triggers volatile outgassing of H2O in addition to SO2, which as long as m clouds leading to a temperature rise of 90º-200º. Exospheric escape of H2O in addition to reaction w/surface minerals causes reduction in cloud cover leading to cooling. Over time atmospheric albdeo in addition to opacity return to normal in addition to temperature equilibrates. The whole cycle lasts 300 million years. SIGNIFICANT RESULTS Features Best Explained by Atmospheric in addition to Surface Interaction Observations tend to validate global climate change model Polygon Plains are found at 204 sites all over Venus Nathan Bridges has mapped Venusian geologic regions About 50% of polygons are near shield volcanoes About 50% of polygons are in regions of varied terrain

Future Mapping May Reveal Polygons as Stratigraphic Markers Venus appears to have experienced a period of high resurfacing rate consistent with volcanic outgassing capable of producing global climate change-if all polygons as long as med in same period, mapping ef as long as ts could explore whether polygons are stratigraphic markers. Section of Fmap 77N355, with a size of 66 x 53 km. Locations “a” show polygons crossing an apparent flow boundary. At “b” a younger volcano covers preexisting polygons. Lower Right Related Papers Anderson, F.S. in addition to S.E. Smrekar, Tectonic effects of climate change on Venus, J. Geophys. Res, 104, 30, 743-30, 756, 1999. Bullock, M. A., in addition to D.H. Grinspoon, The stability of climate on Venus, J. Geophys. Res., 101, 7521-7529, 1996. Bullock, M. A., in addition to D.H. Grinspoon, The recent evolution of climate on Venus, Icarus, 150, 19-37, 2001.

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