In NASAs case, the gas in question is Plutonium-238, used to power deep space probes like the legendary Voyagers and Pioneers and, currently, Cassini probe traipsing around Saturn and New Horizon (name is very much subject to change, as per NASA tradition) as it sashays its way to Pluto and Kuiper Belt.
The unintended, though benign, consequence of nuclear test bans and nuclear arms reduction treaties has resulted in the reliance on Russia for supplies of Plutonium-238, which is running low of late.
Might I suggest a political unpalatable source of limited Plutonium-238: North Korea and Iran.
In North Korea's case, Kim Jong Il will get the hard currency he always sought to fund his movie mogul ambitions and it would solve the problem of North Korea's asinine, but enthusiastic, nuclear armaments program without North Korea losing face.
For Iran, perhaps giving them a chance to gloat extravagantly on how they have become vital to NASA's space program.
Then again Dr. Emmett Brown may just suddenly appear from the future to deliver us that holy grail of 20th century energy: fusion.
Or USS Enterprise (NCC-1701) zooming out from the sun to give NASA the secrets of anti-matter/matter reactor.