New laboratory research
has attempted to figure out how hot water molecules have ended up near the icy
regions of comets. Recent spectroscopic observations of the
gaseous cloud surrounding comets—which are essentially big balls of flying,
dirty ice—have found hot water vapor molecules
within the comet’s coma. No thermodynamic phase change process should lead to hot water being released by the <100K
ice, so how it got there has been quite a mystery.

In cold, ionized media, an
important source of water is the dissociative recombination of the
hydronium ion, H₃O⁺. When a slow-moving electron hits this, one of the
possible reaction pathways leads to neutral water and atomic hydrogen, along with a release of energy. Using a new type of
detection apparatus, researchers from Germany, Israel, and the US examined the relative frequency and associated energies of the various
reaction pathways that occur when D₃O⁺ interacts with an electron.