Free Astronomy Magazine July-August 2021

9 JULY-AUGUST 2021 ASTRO PUBLISHING N ASA Administrator Bill Nelson announced that both DAVINCI+ and VERITAS had been selected. [NASA] ing 167 massive volcanoes that are over 100 km in diameter. At pres- ent, there is limited direct evidence of active volcanism on Venus, al- though indirect evidence exists from measured changes in concen- tration of the volcanic outgassing marker sulfur dioxide. Direct evi- dence of ongoing – or at least very recent – volcanism comes from a study in 2020 by University of Mary- land geophysicist Laurent Montesi and co-workers, who reported that at least 37 of the several hundred named coronae (ring-like structures on the surface caused by the uplift of the crust by heated mat- ter in the mantle) have un- dergone changes indicative of recent volcanic activity. VERITAS will combine spec- troscopy and radar imaging to explore this issue in de- tail. By analyzing rock com- position, scientists will be able to determine which areas are recently cooled magma and which regions have changed due to exposure to the Venusian at- mosphere, providing estimates of either the ongoing extent of, or time since, volcanic activity. Radar mapping may reveal the presence of fault lines – such discoveries would confirm that plate tectonics either is a mechanism of surface change or would at least indicate that such activity once occurred in the planet’s past. A graphic representation of the VERITAS spacecraft orbiting Venus. [NASA/JPL] reshaping of Earth’s surface is obvi- ous when one compares the impact- scarred lunar surface, barely changed in billions of years, with what we find by looking at an Earth map, where near-pristine impact craters are sufficiently rare to count as tourist attractions, and an entire subfield of amateur astronomy is dedicated to scouring satellite im- agery for signs of previously unde- tected ancient impacts. Venus, to our understanding, might lie somewhere in the middle – we do not know if plate tec- tonics is a significant source of surface reconstruction, yet the modern surface is dated to between 300 and 600 mil- lion years old, meaning any large and ancient impacts dating to the early formation of the solar system are rare. The current source of the more youthful Venusian sur- face is believed to be largely volcanic activity from among the over 1600 volcanoes that have been identified, includ-