Venus' steep‐sided domes are circular volcanoes ∼10s of km wide and ∼1 km tall, which are known for their characteristic flat tops and steep sides. However, their composition remains mysterious. These “pancake” domes are likely formed by a high‐viscosity lava, and other studies have predicted a range of compositions, from rhyolite to basalt. In this study, we build on previous work modeling pancake domes as spreading viscous gravity currents. However, previous models of dome formation assumed that they form over a rigid lithosphere. We previously found signatures of lithospheric flexure at 14 out of 75 pancake domes and therefore built a new model of dome formation over a bending elastic lithosphere. We found that flexure during formation can influence the shape of the resulting pancake dome. Our results also support the idea that pancake domes continue to spread for a long time after their emplacement. In comparing our model to the topography of a real pancake dome (Narina Tholus), we find a range of high, though variable, lava viscosities. Our range of lava viscosities is related to the size of the observed dome, and our results for a large dome agree with those of other studies. We test different lava densities and find that a lava density of ∼2,400–2,700 kg/m 3 best reproduces the flexural signatures observed at Narina Tholus. Low‐density lava (∼1,500 kg/m 3 ) does not reproduce the flexural signatures, implying that dome‐forming lava is not highly vesiculated.

Venus diverged from Earth's evolutionary path through the development of a carbon dioxide (CO2)-dominated atmosphere, although studies dispute whether this atmosphere arose shortly after accretion or after a protracted period of surface habitability. Widespread volcanic features suggest that volcanic outgassing may have played a pivotal role in the transformation of Venus. However, the formation of volcanic units on Venus by basaltic lavas can only outgas a minor fraction of the CO2 in the current atmosphere. Here, we model the erosion of long, meandering channels on Venus called canali and show that carbonatite lavas have the unique properties required to erode the canali. Our results suggest that eruption of these carbonatites may have delivered a total mass of CO2 comparable to that of the modern atmosphere, resolving challenges to the formation of Venus' atmosphere within the recent past and suggesting that exoplanets in the "Venus zone" may exhibit the potential for prolonged habitability.

Surface geologic features form a detailed record of Venus’ evolution. Venus displays a profusion of volcanic and tectonics features, including both familiar and exotic forms. One challenge to assessing the role of these features in Venus’ evolution is that there are too few impact craters to permit age dates for specific features or regions. Similarly, without surface water, erosion is limited and cannot be used to evaluate age. These same observations indicate Venus has, on average, a very young surface (150–1000 Ma), with the most recent surface deformation and volcanism largely preserved on the surface except where covered by limited impact ejecta. In contrast, most geologic activity on Mars, the Moon, and Mercury occurred in the 1st billion years. Earth’s geologic processes are almost all a result of plate tectonics. Venus’ lacks such a network of connected, large scale plates, leaving the nature of Venus’ dominant geodynamic process up for debate. In this review article, we describe Venus’ key volcanic and tectonic features, models for their origin, and possible links to evolution. We also present current knowledge of the composition and thickness of the crust, lithospheric thickness, and heat flow given their critical role in shaping surface geology and interior evolution. Given Venus’ hot lithosphere, abundant activity and potential analogues of continents, roll-back subduction, and microplates, it may provide insights into early Earth, prior to the onset of true plate tectonics. We explore similarities and differences between Venus and the Proterozoic or Archean Earth. Finally, we describe the future measurements needed to advance our understanding of volcanism, tectonism, and the evolution of Venus.

Venus is the planet in the Solar System most similar to Earth in terms of size and (probably) bulk composition. Until the mid-20th century, scientists thought that Venus was a verdant world—inspiring science-fictional stories of heroes battling megafauna in sprawling jungles. At the start of the Space Age, people learned that Venus actually has a hellish surface, baked by the greenhouse effect under a thick, CO 2 -rich atmosphere. In popular culture, Venus was demoted from a jungly playground to (at best) a metaphor for the redemptive potential of extreme adversity. However, whether Venus was much different in the past than it is today remains unknown. In this review, we show how now-popular models for the evolution of Venus mirror how the scientific understanding of modern Venus has changed over time. Billions of years ago, Venus could have had a clement surface with water oceans. Venus perhaps then underwent at least one dramatic transition in atmospheric, surface, and interior conditions before present day. This review kicks off a topical collection about all aspects of Venus’s evolution and how understanding Venus can teach us about other planets, including exoplanets. Here we provide the general background and motivation required to delve into the other manuscripts in this collection. Finally, we discuss how our ignorance about the evolution of Venus motivated the prioritization of new spacecraft missions that will rediscover Earth’s nearest planetary neighbor—beginning a new age of Venus exploration.

Topographic moats are found at the edges of Charon's Vulcan Planitia, both where the plains meet the higher elevation terrain in Oz Terra, and surrounding isolated mountains within the smooth plains. The curved edges of the moats have been hypothesized to represent either the front of a cryolava flow from the emplacement of the plains material, or the result of elastic flexure of the plains surface due to the load of adjacent mountains or sinking crustal blocks. We tested both of these hypotheses by taking topographic profiles across the moats and comparing the observations to theoretical predictions from two lava flow models and two plate bending models. The algorithm we used returns a correlation coefficient as well as the parameter values for the theoretical model necessary to match the topography. Our results show that the plate bending models provided the best fits for the topography, though the lava flow models provided good matches for a few profiles. Our results for elastic thickness of similar to 1 km for a continuous plate or similar to 3 km for a broken plate are similar to results previously derived at Serenity Chasma. The values obtained for Bingham yield strength of similar to 10 kPa are also consistent with previous results from hypothesized cryovolcanic material on Ariel and Charon.