Most of the energy we use on Earth in our daily activities is a derivative of solar; wind, hydroelectric, coal, gas (oil), wood fire, solar cells. While we might not think about it, all of these are directly dependent on the Sun and Earth's relative proximity to the Sun.

As PearsonArtPhoto's answer to this question shows; Once lightyears out of the solar system, could you expect to get feasible propulsion with a solar sail? past Mars orbit, Sol's energy is significantly diminished.

What viable & sustainable energy source(s) are available beyond Mars?

  • Where sustainability = no possibility of expending the source prior to the suns natural transition to a red giant in about 7 billion years.
  • Where viable = sufficient energy to sustain the culture and technology to continue the construction of new and replacement tools for harnessing the energy.


  • Solar cells are sustainable but not viable, insufficient surplus energy would be available to process raw materials and construct new cells.
  • Nuclear - is viable but not sustainable as there is finite amount of fissionable material.

2 Answers 2


Jovian magnetosphere is extremely active and stretches nearly all the way to Saturn. It is indeed in volume the second largest continuous structure in the Solar System, right after the heliosphere. Jupiter's radiation in the radio frequencies is in fact so strong, you can tune in and listen to it between frequencies of other radio stations on AM/FM radio receivers. This is a bit of oversimplification, since what you'd hear is a composition of various other celestial bodies emitting radio frequencies (pulsars, the Sun,...), and also Earth's atmospheric charge, but the Jupiter is particularly loud and accounts for the large portion of musical notes in this Cosmic opera.

This radiation in the radio frequencies could potentially be tapped into and converted to electricity. Alternatively, oscillations in magnetic fields as Io orbits Jupiter cause a huge Alfvén wave electric current carried by magnetized ring of ionized gas by between Io and Jupiter. The power of this field is estimated to be around two trillion watts and is the biggest DC electrical circuit in the Solar system known to man. So that are two renewable sources - the electric current, and the highly charged plasma itself.

Io is also highly active itself, constantly being at the mercy of the the enormous gravitational pull of Jupiter. Due to it, it's geologically highly active, and is known to produce volcanic eruptions that eject large amounts of sulfur dioxide gas into space. As such, it is a strong source of plasma. There is also a potential to tap into the geothermal wells and convert that power to electrical current.

There are also other opportunities around Saturn. One idea (admittedly pretty wild, but why not?) that comes to mind is taking advantage of the electrostatic charge of the Saturn's rings. In theory, it's as huge of a collector as they come. Also, the Saturn moon jets, that were detected by the Cassini Solstice Mission carry a potentially huge amount of kinetic, thermal and electric energy in the form of charged plasma.

Thinking farther, all the way to Pluto, tidal forces created by gravitational interaction with Charon as they orbit each other (I can't really say Charon alone orbits Pluto, since they're tidally locked to the other and Pluto orbits a point outside itself) might be strong enough to produce "cryo-geysers" of ammonia hydrates and water crystals on the surface of Charon, as suggested by observations of the Gemini Observatory. And, of course, we already know of other methods of producing electricity by effects of tidal forces - i.e. tidal power.

So these are all sources that can be considered as sustainable. There are all kinds of other opportunities to collect energy in sustainable ways around gas giants, their moons, or even their interaction as they orbit each other. We just need to learn how, and develop technology to convert and/or store all this energy to our liking and needs.

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    $\begingroup$ The tidal gravitational stretching that makes io and the other jovian moons geothermally active would probably also work(although maybe a little less well) around saturn and the other gas giants. Great answer, the jovian magnetosphere is new to me. $\endgroup$ Aug 12, 2013 at 17:42

Not entirely sustainable - but probably more so than Solar (which uses up nuclear fusion of the Sun) - and available pretty much everywhere in the universe, is the Bussard ramjet. Collecting free hydrogen from the space and using it in nuclear fusion. There aren't any sustainable means of collecting meaningful amounts of energy while staying in one place out there, but the space is big; there's a lot of free hydrogen to be collected while traveling, and it can be converted to energy "on the fly", during the travel to some "meaningful" place.

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    $\begingroup$ I'm a bit in doubt which answer is further away from the present technologically, yours or TildalWaves :) $\endgroup$
    – gerrit
    Aug 12, 2013 at 23:06
  • $\begingroup$ @gerrit: Talking about present technology: We don't have reasonable sustainable energy sources for flights beyond Mars, period. Not a very satisfactory answer. $\endgroup$
    – SF.
    Aug 13, 2013 at 0:01

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