Deuterium

Deuterium, also known as heavy hydrogen, was a stable isotype of hydrogen and was used as fuel on starships. With a chemical symbol of ²H, deuterium has a single proton and neutron. It occurs in less than one-half of one percent of naturally-occuring hydrogen.

Deuterium was used in warp reactors, it was injected into warp cores along with its antimatter counterpart, or antideuterium. The annihilation of the two substances within the core released energy used to power warp drives. For storage purposes, deuterium was frozen into a pellet form, and stored in tanks on board starships. In Federation Galaxy-class starships, deuterium was stored in a large tank at the top of the secondary hull.

In the Federation, deuterium was supplied to starships and other installations via fuel carriers. Starships would also supplement their supplies of deuterium by the use of Bussard collectors, which would gather deuterium and other interstellar particles for use on board ships. (TNG reference: Star Trek: The Next Generation Technical Manual)

While performing a survey of a planet in the Hobus star system in 2387, Ayel, science officer of the Narada, detected trace amounts of iridium and deuterium, as well as large deposits of decalithium. (ST comic: "Countdown, Number One")