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I said I'd do a thread about my new Space Science Reviews paper, so here it is! This is part of a collection of papers arising from a meeting at the International Space Science Institute in Bern in 2024: a workshop to better understand rocky extrasolar planets. A 🧵:

The basic idea is that we're finding more and more exoplanets, including ones that—on the basis of radius and mass—are surely rocky. But that's usually all we have, even though it's tempting to call them "super-Earths" or to otherwise attribute (intentionally or not) certain properties to them.

So, until/if we start imaging the surfaces of these worlds, what might we learn about them? Well, we argue that the Solar System's rocky worlds provide a useful template to start from. And that's the gist of the paper! So we start with Earth, Venus, Mars, Mercury, and the Moon.

A big part of the paper (and my career) is comparative planetology, the comparing of one world with another. So in this paper, we talk about how and when the crusts of these worlds developed. Those of Mars, Mercury, and the Moon are ancient; some of Earth is very recent. And Venus?? who tf knows

We take a deep dive into Earth in particular—since it's the world we understand best (even if there's LOTS about Earth we still *don't* understand). Here's a plot showing how we think Earth's bimodal crust grew through time; continental crust wasn't always there, but oceanic crust probably was.

Next is Venus; we talk about its geological history and phenomena as we understand them (which isn't all that well). Here's a global map of Venus' geology; it's important to note that these are schematic maps, designed to be compared with each other. tl;dr: lots of volcanoes, no tectonic plates

Next is Mars*, a substantially smaller world than either Earth or Venus. Mars still has giant volcanoes, rifts, ice caps, and huge impact basins (especially in the southern uplands), but again no sign of plate tectonics. It was too small to replenish the atmosphere lost to space. *spits on floor

We treat Mercury and the Moon together, not so much because they're all that alike but because they're both *small* rocky planets. Lots of volcanism—for a while. But all major geological activity stopped a loooonnnnng time ago on these worlds, because they're small. Anyway, here are their maps.

Do we think anyone else *had* tectonic plates? (or tectonic ice sheets, for moons) How necessary does water seem to be for it, if at all?