VERITAS (VENUS EMISSIVITY, RADIO SCIENCE, INSAR, TOPOGRAPHY AND SPECTROSCOPY): A PROPOSED DISCOVERY MISSION. S. E. Smrekar1, S. Hensley1, M.D. Dyar2, J. Helbert3, and the VERITAS Science Team, 1Jet Propulsion Laboratory, Caltech, 4800 Oak Grove Dr., Pasadena, CA 91109, ssmrekar@jpl.nasa.gov; 2Dept. of Astronomy, Mount Holyoke College, South Had- ley, MA 01075; 3Inst for Planetary Research, DLR, Rutherfordstrasse 2, 12489 Berlin, Germany.

Introduction: VERITAS addresses one of the most eaus and larger tesserae inliers, and for present day fundamental questions in rocky planetary evolution: volcanic outgassing of volatiles in the form of near why did these twin planets diverged down different surface water variability associated with recent or evolutionary paths? Venus may hold lessons for active volcanism. past and future Earth. Venus’ hot lithosphere may Current Activity: Several studies have found be a good analog for early Earth, which may limit evidence of current or recent volcanism on Venus. the development of plate tectonic [1]. Determining [e.g. 10]. VERITAS uses a variety of approaches to the factors that lead to the initiation of plate tecton- search for present day activity, including 1) tectonic ics would inform our predictions for rocky Earth- and cm-scale volcanic surface deformation, 2) sized exoplanets. The conditions leading to Venus’ chemical weathering, 3) thermal emission from re- greenhouse atmosphere may also inform our under- cent or active volcanism, 4) topographic or surface standing of Earth’s future. VERITAS would answer roughness changes, and 5) comparisons to past mis- key questions about Venus’ geologic evolution, sion data sets. determine what processes are currently active, and Gravity: The Magellan spherical harmonic search for evidence for past or present water. gravity field has an average resolution of only 550 Payload: The VISAR X-band [2] measurements km, which is too low to determine elastic thickness include: 1) a global digital elevation model (DEM) [12]. VERITAS data, with an average resolution of with 250 m postings, 5 m height accuracy, 2) Syn- 145 km, will enable estimation of elastic thickness thetic aperture radar (SAR) imaging at 30 m hori- (a proxy for thermal gradient) and resolution of zontal resolution globally, 3) SAR imaging at 15 m specific geologic processes [13]. resolution for targeted areas, and 4) surface defor- Conclusions: VERITAS will create a rich data mation from RPI at 2 mm precision for targeted, set of high resolution topography, imaging, spec- potentially active areas. troscopy, and gravity. These co-registered data will VEM [3] will produce surface coverage of most be on par with those acquired for Mercury, Mars of the surface in 6 NIR bands located within 5 at- and the Moon that have revolutionized our under- mospheric windows and of 8 atmospheric bands for standing of these bodies. VERITAS would be an calibration and water vapor measurements. extremely value asset for future Venus missions, VERITAS will use Ka-band uplink and down- providing a very accurate topography plus surface link to create a global gravity field with 3 mgal ac- composition map to optimize targeting of probe or curacy / 145 km resolution (130 spherical harmonic lander missions as well as for later investigations of degree and order or d&o) and providing a signifi- surface change. cantly higher resolution field with much more uni- References: [1] Bercovici D. and Y. Richard form resolution than that available from Magellan. (2014) Nature 408, 513; [2] Hensley S. et al. (2016) Geologic Evolution: VERITAS answers key VISAR, Intern. Venus Conf. 2016. [3] Helbert J. et science questions via: 1) examining the origin of al. (2018) VEM, this meeting. [4] Dyar M.D. et al. tesserae plateaus -possible continent-like features, (2016), this meeting. [5] Mueller N. et al. (2016) 2) assessing the history of volcanism and how it has this meeting. [6] Bondarenko, N.V. and J.W. Head shaped Venus’ young surface, 3) looking for evi- (2004) JGR 109, 9004. [7] Shalygin et al. (2012) dence of prior features buried by volcanism, and 4) PSS 73, 294. [8] Helbert J. et al. (2008) GRL 35, determining the links between interior convection L11201. [9] Mueller, N. et al. (2008) JGR 113, and surface geology. In particular, VERITAS will E00B17. [10] Smrekar et al. (2010) Science 328. examine the stratigraphy and nature of tesserae de- [11] Konopliv A. et al. (1999) Icarus 139, 3. [13] formation features, determine the processes modify- Wieczorek M. (2007) Treat. Geophy., 10, 165. [4] ing impact craters, search for evidence of pre- Andrews-Hanna J. et al. (2016) LPSCXLVII. existing features such as buried impact basins, and Acknowledgement: A portion of this research determine the origin of tectonic features such as was conducted at the Jet Propulsion Laboratory, huge arcuate troughs that have been compared to California Institute of Technology, under contract Earth’s subduction zones. with NASA. Water and Surface Composition: VERITAS Inst. Planetary Research, German Space Agency looks for the chemical fingerprint of past water in the form of low Fe, high Si rock in the tessera plat-