Italian astronomer Giuseppe Colombo noted that the rotation value was about two-thirds of Mercury's orbital period, and proposed that the planet's orbital and rotational periods were locked into a 3:2 rather than a 1:1 resonance.
Den italienske astronom Giuseppe Colombo havde bemærket at rotationstiden var omkring to-tredjedele af Merkurs omløbstid, og foreslog at en anden type af tidevandslåsning havde fundet sted i hvilken planetens omløbs- og rotationstid var låst i forholdet 3:2 i stedet for 1:1.