The hottest planet’s neighbour keeps ice
Mercury, closest planet to the sun, holds water ice in craters at its poles that sunlight never enters.
Established2 min read
Mercury’s axis is barely tilted. Craters near the poles have floors that are permanently dark and radiatively cold, tens of kelvin. Radar bright patches were suspected for decades. MESSENGER’s neutron spectrometer and imaging confirmed water ice, insulated in places by a dark blanket of organic-rich material.
The ice is not a mystery of climate. It is geometry. No atmosphere to carry heat. No sun on the floor. Deliveries from comets can survive there as they would in a shadowed locker.
Caveats
- The deposits are in specific polar craters, not a global ice cap.
- ‘Hottest planet’ in peak surface temperature is Mercury; Venus is hotter on average because of its atmosphere.
Sources
- 1Paige D. A. et al.. Thermal Stability of Volatiles in the North Polar Region of Mercury. Science 339, 2013.