#BAFact: To the accuracy with which we can measure them, both Mercury and Venus are perfect spheres.

I already posted in previous #BAFact s that Saturn is the flattest planet, and Earth is very nearly spherical; just 0.3% off round. But the roundest planets are Mercury and Venus: to the accuracy we can measure them, they are both perfectly spherical!

Most likely they are not precisely perfect spheres, though. The Sun has a tidal force on Mercury that is 17 times bigger than the Moon's tides on the Earth, so Mercury is stretched out along its equator by many meters at least. However, that's far too small to measure with current technology. The Same goes for Venus; both planets are essentially the ball bearings of the solar system.

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Shared publiclyView activity