Mercury's 59-day rotation (Arecibo radar)
Rotación de 59 días de Mercurio (radar de Arecibo)
- Date
- 1965 · confidence high
- Place
- Arecibo Observatory, Arecibo, Puerto Rico
- Credited to
- Gordon Pettengill and Rolf Dyce
- Field
- Cosmos & Earth
What was discovered
Using radar echoes from the Arecibo radio telescope, Pettengill and Dyce measured in 1965 that Mercury rotates in about 59 days and not in 88 as believed. Giuseppe Colombo noted that this equals two-thirds of its orbital period, a 3:2 spin-orbit resonance.
The 59-day rotation was confirmed by the Mariner 10 probe (1974-75); the current value is 58.646 days. Colombo proposed the 3:2 resonance in 1965.
What it led to
- Mercury's 3:2 spin-orbit resonance and the theory of rotational evolution of planets
- planetary radar as an astronomical technique
- ruling out synchronous rotation for Mercury