91̽»¨

Abstract:

We describe a stratospheric balloon mission that will make continuous observations of Venus over a period of several weeks during the January 2014 inferior conjunction. NASA's balloon program has historically 91̽»¨ed Antarctic flights like this one in the eliophysics and Astrophysics Divisions. The proposed experiment consists of a one meter telescope, two imaging detectors operating from 0.35 to 2.55 ! m at the diffraction limit and 33 filters. This mission will address a number of questions regarding (a) Venus' super-rotation and general circulation, (b) the properties of Venus' clouds, (c) the distribution of trace species and the coupling between certain dynamical and chemical processes, (d) the existence and prevalence of lightning on Venus, and (e) the distribution of thermal emissivity anomalies on Venus' surface. We call this mission VSS (Venus StratoScope) to keep in mind the legacy of the Stratoscope and Stratoscope II balloon missions.

Abstract:

Initial images of Venus's south pole by the Venus Express mission have shown the presence of a bright, highly variable vortex, similar to that at the planet's north pole. Using high-resolution infrared measurements of polar winds from the Venus Express Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a center of rotation displaced from the geographic south pole by ∼3 degrees of latitude and that drifts around the pole with a period of 5 to 10 Earth days. This is indicative of a nonsymmetric and varying precession of the polar atmospheric circulation with respect to the planetary axis.

Abstract:

Physical weathering induced by heating and cooling may cause rock breakdown on Mars and Earth. We report results from parallel weathering simulations on basalt blocks exposed to diurnal cycles representing Mars-like (two simulation runs from -55 to +20 ^oC and -75 to +10 ^oC, 1-100% relative humidity, 4-8 mbar pressure, CO2 atmosphere) and hot arid Earth (23-72^o C, 30-100% relative humidity) conditions. Under Earth conditions, thermally pre-stressed blocks showed measurable strength declines, whilst salt pre-treated blocks showed strength gains. Under Mars-like conditions, pre-stressed blocks recorded greater or similar strength declines and salt pre-treated blocks showed more muted strength declines than under Earth conditions. The results imply that on Earth and Mars diurnal cycling of temperature alone can cause deterioration of basalt with a pre-existing stress history. The type of stress history is important, with salt pre-treatment affecting the response of thermally pre-stressed blocks under both Earth and Mars conditions. Copyright © 2010 by the American Geophysical Union.