November 2021 LIP of the Month

The Potential Role of Large Igneous Provinces in the Great Climate Transition on Venus

M.J. Way^1,2,3, R. Ernst^4,5, Jeffrey D. Scargle⁶

¹NASA Goddard Institute for Space Studies, 2880 Broadway, New York, New York, 10025, USA

²GSFC Sellers Exoplanet Environments Collaboration

³Theoretical Astrophysics, Department of Physics and Astronomy, Uppsala University, Uppsala, SE-75120, Sweden

⁴Department of Earth Sciences, Carleton University, Ottawa, Canada K1S 5B6

⁵Faculty of Geology and Geography, Tomsk State University, Tomsk, Russia

⁶Astrobiology and Space Science Division, NASA Ames Research Center, MS 245, Moffett Field, USA

Earth’s sister planet, Venus, has elevated temperatures of 450C, a dense atmosphere (90 times as dense as Earth’s) which is dominated by CO2 (96%) and the absence of plate tectonics and no significant erosion. However, recent modelling (Way et al. 2016; Way and Del Genio, 2020) has indicated that the climate on Venus could have been more habitable (with a water cycle and possible plate tectonics) through most of Venus’ history with the transition into the current inhospitable conditions having occurred about 1000-700 Myr ago. There is also evidence for this Great Climate Transition preserved in the stratigraphically oldest geologically rocks, termed tesserae.  Curved lineament patterns associated with corresponding topographic changes are consistent with exposure through erosion of sub-horizontally layered units such as flood basalts or even sedimentary rocks (Byrne et al. 2021) and there are paleo-valleys (highlighted by younger lava flooding) which have patterns similar to terrestrial river systems, suggesting formation by fluvial erosion (Khawja et al. 2020).

                 Various models have been proposed for Venus’ Great Climate Transition, and here we consider the potential role of Large Igneous Provinces (LIPs) in causing this transition (Way et al. 2021; Way et al. in prep.).

                 On Earth LIPs are large volume (>100,000 cu. km), often short duration, mainly mafic magmatic events that occur at a frequency (combined continental and oceanic) of one approximately 20 myr (Ernst 2014). LIPs have an origin that is distinct from normal plate boundary processes (Coffin and Eldholm 1994; Ernst 2014), and are linked to intraplate processes. An upwelling mantle plume is typically invoked, but other origins have been proposed (Campbell 2007; Foulger 2007; Ernst, 2014).

                 LIPs are also inferred to be common on Venus.  Venus lacks plate tectonics and therefore all magmatism is by definition intraplate. The largest intraplate events are considered LIP analogues (Head and Coffin 1997; Hanson 2007; Ernst et al. 2007, 2017). Venusian LIP components include large shield volcanoes and coronae, lava flow fields, and plains volcanism and also large radiating and circumferential graben systems (interpreted to overlie dyke swarms). The rate of LIP volcanism is uncertain on Venus given the absence of direct age dating and the uncertainties associated with developing a chronology based on relative ages determined from cross cutting relationships. However, given the similar size and internal structure of Venus to Earth, we provisionally apply the terrestrial rate of LIPs (one per 20 myr) to Venus.

                 On Earth, LIPs are increasingly recognized as a key driver of environmental and biotic change including mass extinction events (Clapham and Renne, 2019; Ernst et al. 2021 and publications and references therein) through a variety of mechanisms: but most notably CO₂ release and associated global warming. The most significant mass extinction, at the 252 Ma Permian Triassic boundary, coincides precisely with the Siberian Traps LIP event (Figure 1) and there is consensus that this LIP was responsible for this mass extinction (Burgess et al. 2015) and was associated with a large temperature increase that may have reached a global average of 40C (Sun et al. 2012; Scotese et al. 2021).

                 There are various causes proposed for the origin of runaway global warming on Venus, including the role of LIPs (e.g. Way and Del Genio, 2020). We evaluate whether the proposed Great Climate Transition on Venus, from habitable to present day hyper-warm with high CO₂, may be associated with stochastic overlap of multiple LIPs leading to extreme runaway greenhouse conditions (Way et al. 2021; Way et al. in prep.).

                 If LIPs were responsible for the Great Climate Transition on Venus, then we might also speculate whether such superimposed LIP events and resulting catastrophic climate change could occur in Earth’s future, in 10s to 100s of myr (Fig. 2).

Reference