Earth and Venus seem to be in a long-distance relationship, for planetary scientists have claimed that our planet could be tugging on the core of Venus, exerting control over its spin.

Whenever Venus and Earth arrive at the closest point in their orbits, the former always presents the same face to us. This could mean that Earth’s gravity is tugging subtly on Venus, affecting its rotation rate.

That idea, raised decades ago, was disregarded when it turned out that Venus is spinning too fast to be in such a gravitational “resonance”.

But, new calculations by a team led by Grd Caudal of the University of Versailles, Saint Quentin, France, has suggested that plane Earth could still be pulling on Venus by controlling its core, the New Scientist reported.

For his hypothesis to be correct, the planet would, like Earth, need a solid core surrounded by a liquid layer.

This could allow the solid core to rotate slower than the rest of the planet, say the scientists.

The core would also have to be asymmetric or heterogeneous, so that Earth can exert a variable tug as Venus spins. “For the resonance to be possible, there should be something that the gravity of the Earth could grasp,” Caudal said.

However, Jean Luc Margot of University of California said that this latter requirement could be problematic for the hypothesis. “In order to maintain a resonance, the inner core must be out of round by a significant amount.”

Yet persistent imperfections in planetary cores tend to smooth out because the core is hot and under great pressure, according to David Stevenson of the California Institute of Technology in Pasadena. “Still, the resonance theory is worth revisiting.”

“Watching for changes in Venus’s spin over time using radar observations may reveal more about what’s going on inside the planet,” said Margot.

The findings have been published in the Journal of Geophysical Research.

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