Its just an isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen. Deuterium thus accounts for approximately 0.015% (on a weight basis, 0.030%)of all naturally occurring hydrogen in the oceans on Earth. Deuterium abundance on Jupiter is about 6 atoms in 10,000 (0.06% atom basis). There is little deuterium in the interior of the Sun, since thermonuclear reactions destroy it. However, it continues to persist in the outer solar atmosphere at roughly the same concentration as in Jupiter. On the other hand, antimatter seems so plentiful in all versions of Trek. The U.S. has been manufacturing antimatter for more than 30 years... and the sum total produced is a fraction of a gram. I understand why deuterium might have been a "rare" find in TOS era of science, but during the Voyager and Enterprise era, exactly what deuterium is, and its relative scarcity, was well known. Yep, I'm the first one to admit this is WAAAAY picky, but Trek writers, even back to TOS, were pretty sharp, all things considered. By and large, I just enjoy Trek... but I've always been curious about the "scarcity" of deuterium on modern Trek. Any thoughts?