The simple molecular ion H3+ has been known in the laboratory since 1911, when it was discovered by JJ Thomson while carrying out experiments on “rays of positive electricity”. It is stable, but highly reactive, making it an initiator chemical changes in mixed gases such as planetary atmospheres and the interstellar medium.
The enormous anharmonicity of its vibrational modes means that has strong infrared emission bands throughout the near-infrared. This enables it to play the role of a “thermostat” even when temperatures reach >2500K. As a charge carrier, a provider of conductivity, H3+ also plays a pivotal role in energy generation in planetary atmospheres.
And finally – and not altogether tongue-in-cheek – it may turn out to have been the saviour of the Solar System as we know it. Not bad for such a little molecule!