Plate tectonics is crucial for habitability of terrestrial planets

We argue that the habitability of terrestrial planets is linked to plate tectonics. We base our proposal on two premises.

First, in the absence of a robust magnetic field, a planet’s atmosphere is vulnerable to stripping by the solar wind, leading to catastrophic water loss and, ultimately, sterilization, as exemplified by modern Mars and Venus.

Second, a strong intrinsic planetary magnetic dipole must be generated by vigorous convection in the liquid core, which in turn requires efficient removal of heat from the core. On Earth, this heat removal occurs through the operation of plate tectonics.

The contrasting evolutionary paths of Earth, Venus, and Mars provide a natural laboratory for examining these relationships. Unlike Earth, both Mars and Venus lack plate tectonics and simultaneously lack a strong magnetic field. Venus currently operates in a stagnant-lid regime, in which heat loss occurs primarily by conduction across a thick lithosphere. This mode of heat transfer appears insufficient to sustain a core dynamo, resulting in the absence of a magnetic field and, consequently, in the loss of water and the development of an uninhabitable environment.

Another key “experiment” is recorded in Earth’s own history at the end of the Ediacaran period. This interval was preceded by approximately 1.5 billion years of a gradual decline in Earth’s dipole moment, from values comparable to the present field to a minimum that was roughly 30 times weaker. This minimum field strength persisted between 591 and 565 Ma, followed by a rapid threefold strengthening by about 532 Ma. Concurrently, atmospheric and oceanic oxygen levels began to rise, supporting an increase in the abundance and size of living organisms. These developments are commonly attributed to the formation of the inner core around ~550 Ma. However, both inner core growth and the associated intensification of the magnetic field would have been impossible without the simultaneous onset of plate tectonics. Thus, it was this tectonic regime change that enabled the rapid expansion of habitability at the Precambrian–Phanerozoic boundary.

We conclude that, although direct evidence remains limited, current scientific understanding strongly supports the notion that Earth’s long-term habitability is linked to the operation of plate tectonics, which sustains the geodynamo and protects the atmosphere from erosion by the solar wind. Nevertheless, the fundamental question of why Earth retained a functioning dynamo through plate tectonics, whereas Mars and Venus did not, remains an open problem for future investigation.