How our Moon and Sun may affect Earth's equatorial bulge

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SUMMARY

The discussion centers on the factors influencing Earth's equatorial bulge, specifically comparing it with Mars. Earth's equatorial bulge is measured at 3%, while Mars exhibits a 6% bulge despite similar rotation periods. This discrepancy is attributed to Mars's colder mantle and significantly higher viscosity, estimated to be 10 to 100 times that of Earth's. The impact of the Moon's tidal forces on Earth's bulge is debated, with the consensus indicating that the size difference between the planets plays a more critical role than tidal effects.

PREREQUISITES
  • Understanding of planetary rotation and its effects on shape
  • Knowledge of viscoelasticity in planetary science
  • Familiarity with gravitational acceleration and its implications
  • Basic concepts of equatorial bulge measurement
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  • Research the viscoelastic properties of planetary mantles
  • Explore the relationship between planetary size and equatorial bulge
  • Investigate the effects of tidal forces on planetary shapes
  • Study comparative planetary geology, focusing on Earth and Mars
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Astronomers, planetary scientists, geophysicists, and anyone interested in the dynamics of planetary shapes and their geological implications.

lunatectonics
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the equatorial bulge of a planet is affected by the planet's rotation and viscoelasticity of the sphere. Venus's rotation period is 244 days with an equatorial bulge of 0%. Earth's and Mars's rotations are almost identical at 1 day and 1.03 days, yet Mars's equatorial bulge is 6% vs Earth's 3%. Mars has has a colder mantle with viscosity estimated 10 - 100 times earth's viscosity.

Given that Earth's shell is more mobile and responsive to deformation , what would be Earth's equatorial bulge % if the Moon's tidal forces were not squeezing it ? the sun being constant with both Mars and Earth.
 
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It sounds like you're saying you think the moon impacts the Earth's equatorial bulge, decreasing its size vs Mars'. The equatorial bulge is much, much larger than the tides (and exists around the entire equator), so it doesn't explain the difference. The difference is probably explained by the difference in size between the planets. A smaller planet has a smaller tangential velocity but a much smaller gravitational acceleration at the surface.
 
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lunatectonics said:
Mars's equatorial bulge is 6% vs Earth's 3%
To what are the 6% and 3% comparison referring.
Equator to North-South pole diameter, or something else.
 
russ_watters said:
It sounds like you're saying you think the moon impacts the Earth's equatorial bulge, decreasing its size vs Mars'. The equatorial bulge is much, much larger than the tides (and exists around the entire equator), so it doesn't explain the difference. The difference is probably explained by the difference in size between the planets. A smaller planet has a smaller tangential velocity but a much smaller gravitational acceleration at the surface.
The earth's Equator to North-South pole diameter bulge is more close to theoretical, and Mars is out is whack.
If anything, Mars needs explaining.
 

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