Extraterrestrial lava lakes

Active lava lakes are rare on Earth, with only ten documented examples, all formed by lavas of basaltic composition and housed inside summit craters or calderas. The existence of lava lakes on other planetary bodies may imply similarities in either composition or volcano-tectonic settings, and so has important implications for understanding the link between melt production and volcanism. We review lava lakes on Earth and other planets, particularly active caldera-like features interpreted to be currently containing active lava lakes on Jupiter's moon Io, and features interpreted as remnants of lava lakes on Venus and Mars. Mercury and the Moon do not boast the major calderas or shield volcanoes of their larger rocky neighbors, partly due to a horizontally compressive tectonic regime arising from global contraction that makes it difficult to move melts through the upper crust. We discuss the evidence for active lava lakes on Io and show how modeling based on terrestrial lava lakes can reveal how these phenomena differ on both bodies; the superficial similarities do not necessarily imply that the plumbing is similar. Observations of the largest lava lake on Io, Loki Patera, provide insight into the nature of Ionian lava lakes in general, which may be more similar to eruptive episodes on the East Pacific Rise on Earth, which lead to temporary lava lakes. Although temporal data for Io's lava lake activity are scarce, studies of temporal variability of lava lakes on Earth are useful for providing ground truth for comparisons. Future studies of Earth by remote sensing and field observations, and of Io by both ground-based observations and future missions, are needed to answer many questions, including why lava lakes, rare on Earth, appear to be common on Io.