Ivan López

Several missions to Venus have recently been selected for launch, opening a new era for the exploration of the planet. A key question these missions seek to address is whether Venus is geologically active today. Detecting active volcanism on Venus would contribute to a better understanding of volcanic and atmospheric processes on Earth. The Analogs for VENus' GEologically Recent Surfaces (AVENGERS) initiative provides a comparative framework for the identification and analysis of terrestrial analog sites relevant to recent and possibly ongoing volcanic activity on Venus. Although this review focuses on terrestrial analogs for Venus exploration, the AVENGERS initiative also includes investigations that use Venus and Earth as analogs to better understand the evolution of terrestrial exoplanets. In addition, the AVENGERS initiative facilitates international collaboration by connecting Venus mission teams with the broader planetary and exoplanetary science communities. This review describes the scientific context of AVENGERS, details the selection criteria for terrestrial analog sites, and summarizes a set of suitable locations. Methodological approaches in analog studies that support the interpretation of Venus observations are also discussed.

The selection of three new missions to Venus opens a new era to explore the planet and its evolution: ESA’s EnVision and NASA’s VERITAS and DAVINCI missions plan to observe Venus in the next decade. ESA and NASA established a joint Venus Science Coordination group (VeSCoor) as a forum for dialogue within the broader Venus scientific community, in support of the upcoming ESA and NASA missions to Venus [1].The NASA VERITAS mission will study the surface and interior with an interferometric synthetic aperture radar and infrared instrument that provide global topography, imaging, rock type, and targeted surface deformation, plus radio science for interior structure [2].The NASA DAVINCI mission a descent probe that will determine the composition and history of Venus’ atmosphere as well as make additional measurements of the planet’s surface and atmosphere. DAVINCI consists of a spacecraft hosting a carrier and a descent probe, with seven in-situ, imager and spectrometer instruments [3].EnVision, an ESA orbital mission in collaboration with NASA, will simultaneously investigate Venus’ history, activity and climate, from its inner core, to its surface, and further up to its upper atmosphere. EnVision’s science payload consists of five instruments (radar, spectrometers, sounding radar and radio science experiment) [4].These missions will offer unprecedented complementary views of Venus and determine fundamental characteristics of the planet and its long term evolution [5, 6].In this scenario, VeSCoor’s primary goals are to identify new, unanticipated scientific approaches and outcomes based on synergies among the missions to Venus and suggest studies to enhance overall scientific return. However, VeSCoor will not evaluate or propose changes to the current mission profiles, scientific objectives, or requirements.The group was initially made up of 12 members from the Venus science community (Figure 1), 6 selected by ESA and 6 by NASA, plus 3 representatives of the EnVision, VERITAS and DAVINCI missions [7]. Membership in VesCoor is initially set to a 2 year term, but may be renewed at the discretion of NASA and ESA. A scientific observer from South Korea has subsequently joined the group along with two members selected by JAXA.VeSCoor members’ expertises cover different scientific disciplines to provide a comprehensive view of Venus as a planet, and hence, as a complex system.Representatives from NASA and ESA agencies are involved as observers to provide support to the group’s activities.The Group meets in-person twice a year to discuss science objectives and receive updates on the missions’ development. The outcomes of the discussion will be part of public documents available soon. Three working groups (Interiors, Surfaces, and Atmospheres) have been created to address the identified topics, and to discuss specific actions that could facilitate progress in advance of the missions.The first in-person meeting was held in February 2024 in Virginia, USA (Figure 2). Mission representatives from VERITAS, EnVision, and DAVINCI presented descriptions of mission science payloads, timelines, expected science returns, and current activities. VeSCoor members worked on developing the "Rules of the Road" document that establishes rules of conduct and communication.The second in-person meeting of VeSCoor was held in the ESA ESTEC establishment on November 2024 (Figure 3). We included in the discussion the Earth-based observation of Venus and talked about the Korean earth-based satellite for Venus exploration (CLOVE) [8].To improve the scientific discussion, four speakers were invited to present specific topics identified by the Group as strategic:- Sara Seager presented the ‘The search for life in the Venus’ clouds’ goal of the Morning Star mission.- Sebastien Lebonnois presented a review on the Venus Global Climate Models.- Edgar Steenstra talked about his recent laboratory set up to support the EnVision observations.- Lorenzo Bruzzone, PI of the radar Sounder SRS onboard EnVision presented the objectives and foreseen capabilities of this instrument to explore the subsurface of Venus.The third in-person meeting of VeSCoor was again held at the Lansdowne Resort in Leesburg in March of 2025 (Figure 4). The group received updates on NASA developments from Delia Santiago-Matarese, and status reports from EnVision, VERITAS, and DaVinci mission leadership. Three speakers were invited this time:- David Grinspoon (NASA’s Senior Scientist for Astrobiology Strategy) discussed the Astrobiological Potential of Venus.- Michael Chaffin presented the Photochemical Hydrogen Loss from Venus and the Fate of an Earth-like Water Inventory.- Debra Buczkowski described the status of the Venus Geologic Mapping Efforts.The preliminary results of the discussion emphasize the importance of on-going studies and experimental work in preparation for the new missions.The importance of completing the Venus mapping programme and generating ongoing discussion on common mapping standards for the international Venus community was emphasized. Also, facilitation of analog field studies to test the instrument performance, operational routine and scientific data integration was supported.International collaboration is fundamental to unite the efforts for successful exploration of Venus.The Group also discussed the need to establish workshops for the international Venus community (COSPAR, etc.) and maintain contact with other Venus-focused groups (i.e., VEXAG).Acknowledgments:The Group would like to express their thanks to ESA and NASA representatives for supporting our activities and particularly to Ramon De Paula who has recently retired from NASA.References: [1] NASA-ESA Venus Science Coordination (VeSCoor) – Terms of Reference 2022, [2] Smrekar, S.E. et al. (2022) In: 2022 IEEE aerospace conference; [3] Garvin, J.B. et al. (2022) Planet Sci J 3:117;...

Large topographic rises on Venus are regions thought to be formed in response to the presence of a mantle plume or mantle upwelling, equivalent to hot spots on Earth. In this work, we study the geology and evolution of one of these large topographic rises, Imdr Regio, based on geologic mapping and analysis of geophysical data of the area. Imdr Regio presents a complex structure with two very different areas: (a) an elevated southeast area that is dominated by volcanism associated with Idunn Mons, a large volcano that has been proposed as a site of recent or even active volcanism; (b) another elevated area in the northwest area that also has a large volcano (Arasy Mons), but that is dominated by volcanism and tectonic activity associated with the formation of the Olapa Chasma rift system. These two very differentiated topographically elevated areas also exhibit differences in their geology, volcanic and tectonic style, and geophysical characteristics, which leads us to suggest that more than the classic volcano‐dominated rise classification attributed to Imdr Regio the area could rather be considered as an intermediate or hybrid volcano‐rift dominated large topographic rise. The evaluation of the different genetic scenarios and its correspondence with the observed geology in the area suggests that the complex geology of Imdr Regio could be better explained if we consider models of hot spot evolution that involve the presence of several mantle plumes or secondary upwellings derived from a mantle plume emplaced at a deeper rheological boundary.

Characterisation of surface deformation at stratovolcanoes is essential for a better understanding of the processes that can compromise edifice structural stability and potential for flank collapse. Spreading produced by the presence of a hydrothermal system or intrusion of a viscous magma body can produce similar deformation signatures, and both processes have implications for flank instability. In this work, we perform analogue models and consider examples from real volcanoes (Damavand, Ubinas, Semeru and Casita) so as to characterise and recognise surface deformation patterns produced by spreading due to the presence of a hydrothermal system and in response to magma intrusion. The experiments show that there are differences in the resulting surface deformation associated with each process. Magma intrusion results in a sharp transition between areas of subsidence and uplift, and is associated with faults with oblique strikes in the upper part of the edifice. Instead, asymmetric flank spreading is associated with hydrothermal system and results in flank bulging close to the base of the edifice. Although laboratory analogue models show different deformation responses that could be diagnostic of the associated processes, application in the field is difficult as often these diagnostic features are not preserved during evolution. However, basal bulging represents a potential diagnostic for the identification of asymmetric volcano flank spreading associated with hydrothermal activity, and the potential for instability. Remote sensing techniques can allow identification of such surface deformation features, providing a useful tool for hazard assessment and design of monitoring strategies at potentially unstable volcanoes.

The recently selected NASA VERITAS and DAVINCI missions, the ESA EnVision, the Roscosmos Venera‐D will open a new era in the exploration of Venus. One of the key targets of the future orbiting and in situ investigations of Venus is the identification of volcanically active areas on the planet. The study of the areas characterized by recent or ongoing volcano‐tectonic activity can inform us on how volcanism and tectonism are currently evolving on Venus. Following this key target, Brossier et al. (2022, https://doi.org/10.1029/2022GL099765) extend the successful approach and methodology used by previous works to Ganis Chasma in Atla Regio. Here we comment on the main results published in Brossier et al. (2022, https://doi.org/10.1029/2022GL099765) and discuss the important implications of their work for the future orbiting and in situ investigation of Venus. Their results add further lines of evidence indicating possibly recent volcanism on Venus.

The recently selected NASA VERITAS and DAVINCI missions, the ESA EnVision, the Roscosmos Venera-D will open a new era in the exploration of Venus. One of the key targets of the future orbiting and in-situ investigations of Venus is the identification of volcanically active areas on the planet. The study of the areas characterized by recent or ongoing volcano-tectonic activity can inform us on how volcanism and tectonism are currently evolving on Venus. Following this key target, the manuscript by Brossier et al. (2022) (https://doi.org/10.1029/2022GL099765) extends the successful approach and methodology used by previous works to Ganis Chasma in Atla Regio. We comment here on the main results of the manuscript published by Brossier et al. (2022) (https://doi.org/10.1029/2022GL099765) and discuss the important implications of their work for the future orbiting and in-situ investigation of Venus. Their results add further lines of evidence indicating possibly recent volcanism on Venus.

In 2010 the ESA Venus Express Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument first observed 1 μm emissivity anomalies over the top and eastern flank of Idunn Mons (46° S; 146° W), a 200 km wide volcano located in Imdr Regio, a volcano-dominated large volcanic rise of Venus. The anomalies suggest the presence of chemically unweathered and fresh volcanic deposits, which provided the first hint that volcanism in this area may have been active during the past few million years. Subsequent studies have investigated the geologic and atmospheric evolution at Idunn Mons, but no study has comprehensively investigated the evolution and the implication for recent activity in Idunn Mons. Previous work, using both VIRTIS data and Magellan radar emissivity data, confirmed the occurrence of unaltered basaltic lava flows at Idunn Mons. Building on that previous work, experimental laboratory studies have revealed that chemical weathering on Venus may act much faster than previously expected, which suggests very young ages for these flows. This inference has been supported by investigations of the tectonic fracturing surrounding Idunn Mons. Finally, atmospheric data from VIRTIS also show regional anomalies in the speed of the winds in the lower atmosphere over Imdr Regio, which may be related to very recent or ongoing volcanism. In this paper, we take a comprehensive approach, using atmospheric to surface measurements, including recent laboratory experiments, to constrain the evolution of Idunn Mons. Our work suggests that Idunn Mons may be geologically both volcanically and tectonically active today.

Combining geologic mapping and stratigraphic reconstruction of lava flows at Sapas, Maat and Ozza Montes, three potentially young volcanic structures of Atla Regio on Venus, with analysis of the spectral signature (radar emissivity anomalies) characterizing each mapped flow, Brossier et al. (2021, https://doi.org/10.1029/2020je006722), conclude that some of the lava flows at Maat Mons may be geologically recent (∼25 Ma) (Smrekar et al., 2010, https://doi.org/10.1126/science.1186785; D'Incecco et al., 2017, https://doi.org/10.1016/j.pss.2016.12.002; Zolotov, 2018, https://doi.org/10.1515/rmg.2018.84.10; Brossier et al., 2020, https://doi.org/10.1016/j.icarus.2020.113693, 2021, https://doi.org/10.1029/2020je006722). The lava flows of Sapas and Ozza Montes are consistent with weathered lava flows forming chlorapatite and some perovskite oxides. We discuss the reasons why, besides the importance of the results they obtained, the methodology they used can be very valuable for future investigations with higher resolution datasets.

Combining geologic mapping and stratigraphic reconstruction of lava flows at Sapas, Maat and Ozza Montes, three potentially young volcanic structures of Atla Regio on Venus, with analysis of the spectral signature (radar emissivity anomalies) characterizing each mapped flow, Brossier et al. (2021) conclude that some of the lava flows at Maat Mons may be geologically recent (~25 Ma). The lava flows of Sapas and Ozza Montes are more consistent with weathered lava flows forming chlorapatite and some perovskite oxides. We discuss the reasons why, besides the importance of the results they obtained, the methodology they used can be very valuable for future investigations with higher resolution datasets. The importance of combining geologic interpretation with spectral analysis in the reconstruction of the volcanic history of Venus Considering its size, gravity and the presence of an atmosphere, Venus is typically considered as the twin sister of the Earth, but despite the apparent similarities with our planet, Venus is notably different because it is characterized by its extreme surface environment. With 90 bars and 475 °C, its surface is a very inhospitable place for life as we know it. Venus does not show evidence for a present plate tectonics-like activity, having a major part of its surface volcanic deposits younger than 300 Ma. It has been hypothesized that Venus underwent a catastrophic event of global resurfacing about 300 Ma ago, which may have almost entirely rejuvenated its surface (Schaber, 1992; Nimmo and McKenzie, 1998; Romeo and Turcotte, 2010; Strom et al., 1994; Turcotte et al., 1999). Some other studies instead favor a more equilibrium resurfacing model of the surface (Phillips et al, 1992; Phillips and Hansen, 1994; Bjonnes et al., 2012; O’Rourke and Korenaga, 2015). It is also possible that the past volcanic history of Venus somehow reflected an intermediate situation between these two end-member scenarios. Related to this topic, there has been a subject of debate whether or not the volcanism on Venus is currently evolving toward an equilibrium stage, with occurrences of smaller and more frequent localized eruptions. In this regard, it is vital to identify areas with current or recent volcanism, to measure the actual rate and volume of the most recent volcanic eruptions. The geologic interpretation and analysis of spectral signatures (both in radar and infrared wavelengths) can help us constraining the age of surface volcanic deposits on Venus. In geology, the so called “cross-cutting interrelationships” can constrain the relative age of two lava flows as it has been applied to young, possibly very recent lava flows and tectonic features on