The space.com article says, "The length of Mars’ day is shortening by three-quarters of a millisecond each year as the planet’s rotation spins up, according to new results from NASA’s InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission."
My thoughts, this is quite a bit of spin rate change. 7.5x10^-4 s per year. 4.5 billion years, 3.375 x 10^6 second change in Mar's LOD or more than 39 hours in Mars LOD change. The article stated, "The experiment used data from InSight’s first 900 days on Mars and concluded that Mars’ rotation is speeding up by 0.76 milliseconds per year – the most precise measurement of Mars’ rotation period ever made."
This is slightly larger, 3.42 x 10^6 second change when extrapolated over 4.5 Gyr period. What was Mars original LOD when it first appeared, accreted from the postulated solar nebula and protoplanetary disc? There could be the proto-mars LOD and later, the Mars LOD after some postulated giant impact perhaps. Now today, Mars is spinning faster and faster it seems.
The origin of the terrestrial planets,
https://arxiv.org/abs/2305.18635, 29-May-2023. "Three major planets, Venus, Earth, and Mercury formed out of the solar nebula. A fourth planetesimal, Theia, also formed near Earth where it collided in a giant impact, rebounding as the planet Mars."
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