The Martian core, the Insight expedition tells us, is wholly liquid with no solid centre. Earth’s core is solid, and spins, inside a liquid “outer core” shell. Earth’s core delivers a magnetic field which prevents our ionosphere from escaping - thus allowing a stable atmosphere. Mars' liquid core is "compressible" but the planet hasn't outer mass sufficient to compress any of it into solid. Mars' atmosphere is now almost all ionosphere and too thin for life.
This came to us from Tuesday, widely shared yesterday across several university sites, thence to the science blogs.
Before then I'd always been told that Mars used to own a magnetic field, wayyy back in its Noachian. This study assumes that the magnetism was present up in the upper mantle and crust, not the core.
Maybe. Could Mars' core once had a solid ball of iron within it? We'd then have to ask how a solid core liquifies over time rather than growing more solid, as here. Do the sulfur, carbon, oxygen and hydrogen anneal themselves into the iron ball in high pressures, and lower its melting-point? I'd thought that iron-rust melts at a higher temperature than pure iron (with siderophiles like nickel) and that, further, it would be stiffer. Also I'd thought carbon oxides tend to pull/push oxygen with iron - to "reduce" or to rust it respectively - not to join with it. I admit that's under 1-bar pressures.
Zim is saying that we need more Insight installations, to triangulate all this.
UPDATE 10/18/23: the 4 May '22 quake was tectonic.
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