Scientists from the Royal Observatory in Edinburgh have said that judging by the chemical composition of stars in the Milky Way, our galaxy could contain anywhere between 300 and 38,000 highly developed extraterrestrial civilizations potentially capable of contacting planet Earth.
Although current generations are unlikely to shake hands with little green men from Mars, humankind has already discovered sizeable mineral deposits on other planets. But should we pin any hopes on them?
Cassini-Huygens, a joint robotic space mission promoted by US space agency NASA, the European Space Agency and the Italian Space Agency, currently studying the planet Saturn and its moons, has discovered oil and gas deposits on Titan, Saturn's largest satellite. The estimated reserves exceed terrestrial deposits by some 100 times.
Previous images received from Cassini-Huygens indicated rain and snowfall on Titan. Although the discovery of oil and gas deposits on this moon is hardly sensational, it could help scientists explain the origin of life on the Earth.
Many scientists and analysts say extraterrestrial sources of energy could provide humankind with enough heat and energy for hundreds of years to come and would help it cope with a snowballing energy crisis.
The newly discovered hydrocarbon deposits inside 15 large lakes on Titan could provide enough power for all US heaters, lamps and air conditioners for hundreds of years. Hydrocarbons contained inside huge dunes covering 20 percent of Titan's surface exceed the Earth's coal deposits by several hundred times.
In addition, some regions on Mars have high concentrations of methane. Next autumn, NASA plans to launch another Mars exploration vehicle for studying methane deposits on the Red Planet and their origin.
However, extraterrestrial deposits are highly unlikely to solve current energy shortages.
First of all, we know nothing about the quality of Titan oil. Scientists from NASA's Jet Propulsion Laboratory (JPL) know only that a local lake contains ethane, a crude-oil ingredient.
A manned mission to Titan is still the fantasy of science fiction novels and would face the same mind-boggling problems as a mission to Alpha Centauri, the closest star system to our own solar system, at only 4.37 light years from the Sun.
Moreover, even the most optimistic science fiction writers do not know when it will become possible to launch prospecting operations on Titan at minus 180 degrees Celsius.
Also, no one knows whether the world will still require oil a hundred years from now when long-range space missions to other planets could become commonplace.
Current alternative fuel programmes could eventually replace oil with corn and other grain crops. If so, extraterrestrial oil would not play an important global economic role in the near future.
Scientists propose using the light and non-radioactive helium-3 isotope as a second-generation fusion power source. It is believed that the Moon contains far more helium-3 than the Earth.
Many Russian scientists believe this would be the real motivation for colonizing the Moon, which abounds in helium-3. The tremendous lunar helium-3 deposits would be expected to facilitate an energy revolution and eliminate global fuel shortages.
Although this is a feasible task, it would be inappropriate to try and exploit helium deposits. Lunar soil samples delivered to the Earth by Soviet Luna probes and US Apollo spacecraft were found to contain a relatively high amount of helium - 0.01 grams per tonne. But the Moon does not have any helium lakes and this isotope is spread thin all over its surface.
Supposing that the world eventually solves the problem of controlled thermonuclear fusion, it would then annually require about 100 tonnes of helium, an amount that can be carried by several US Space Shuttles.
But this amount is contained inside a billion tonnes of lunar rock that would have to be processed in a hostile space environment. Moreover, a global energy revolution will require tens of billions of dollars and is still decades away.
This is why it is unrealistic to count on distant extraterrestrial deposits. Posterity should decide whether lunar and Martian natural resources are worth exploiting, after all.