
Figure 1: The terrestrial planets of our solar system: Mercury, Venus, Earth, and Mars[5]
In 2017, a new way of understanding the cooling and heat transfer of terrestrial planets was proposed by a team of scientists from NASA and Louisiana State University[1].

Figure 2: Image of Jupiters moon, Io showing its surface eruptions.[6]
Heat-pipe cooling/tectonics is a method of cooling for terrestrial planets wherein the main heat transport mechanism present on the planet is volcanism originating below the lithosphere, shown below in the top of figure 3. (stagnant-lid convection is discussed below as well)[4]. Melted rocks and volatile materials are moved from the liquid mantle through the lithosphere via vents and volcanic eruptions. These eruptions lead to global resurfacing of the planet by which older layers are buried and pushed down to form the thick, cooler lithospheres that contain the tectonic plates we are all familiar with.

Figure 3: Modeled lithospheric thickness for heat-pipe and stagnant-lid planets.[7]
The hallmark of heat-pipe cooling is the resultant strong lithosphere in addition to the constant resurfacing of the body due to persistent volcanic activity. The implications of heat pipes for the tectonic history of terrestrial planets are shown in figure 3 above. Planets that evolve through a heat-pipe cooling phase develop a thick lithosphere early in their history which subsequently thins as volcanism wanes and thickens as stagnant-lid convection takes over. This is where the surface of a terrestrial planet has no active plates and is instead locked into one giant plate, and the surface material does not experience subduction[3]. Currently Earth does have active plates as evident by our abundant seismic activity, but this form of convection will eventually become dominant, and the lithosphere will no longer be recycled. At this stage, whatever condition the Earth’s surface is in will be preserved for extraterrestrials to view and study, similar to how we study other planets.
References:
[1]https://www.nasa.gov/press-release/scientists-propose-new-concept-of-terrestrial-planet-formation
[2]https://agupubs.onlinelibrary.wiley.com/doi/10.1029/JB094iB03p02779
[3]https://www.ucl.ac.uk/seismin/explore/convection-seismology.html
[4]https://reader.elsevier.com/reader/sd/pii/S0012821X17303242?token=73C931FE15DBD35C37DA2C96C433469E88F52DECB1E47D5F682C25DE4B7BE3D4150B372850444879131FDD450CDBD971&originRegion=us-east-1&originCreation=20220512121740
Image sources:
[5]https://solarsystem.nasa.gov/resources/687/terrestrial-planet-sizes/
[6]https://solarsystem.nasa.gov/resources/1039/galileo-sees-io-erupt/
[7]https://www.sciencedirect.com/science/article/pii/S0012821X17303242