Washington, Dec 18 (IANS) “Avatar”, the latest blockbuster from Hollywood, showcases a human-visit to the inhabited alien moon called Pandora.
Life-bearing moons like Pandora or the Star Wars forest moon of Endor are a staple of science fiction. With NASA’s Kepler mission showing the potential to detect earth-sized objects, habitable moons may soon become science fact.

If we find them nearby, a new study by Smithsonian astronomer Lisa Kaltenegger shows that the James Webb Space Telescope (JWST) will be able to study their atmospheres and detect key gases like carbon dioxide, oxygen and water vapour.

“If Pandora existed, we potentially could detect it and study its atmosphere in the next decade,” said Lisa Kaltenegger of the Harvard-Smithsonian Centre for Astrophysics (CfA).

Kaltenegger calculated what conditions are best for examining the atmospheres of alien moons. She found that alpha Centauri A, the system featured in “Avatar”, would be an excellent target. It is “a bright, nearby star very similar to our Sun,” Kaltenegger added.

So far, planet searches have spotted hundreds of Jupiter-sized objects in a range of orbits. Gas giants, while easier to detect, could not serve as homes for life as we know it.

However, scientists have speculated whether a rocky moon orbiting a gas giant could be life-friendly, if that planet orbited within the star’s habitable zone (the region warm enough for liquid water to exist).

“All of the gas giant planets in our solar system have rocky and icy moons,” said Kaltenegger. “That raises the possibility that alien Jupiters will also have moons. Some of those may be earth-sized and able to hold on to an atmosphere.”

Kepler looks for planets that cross in front of their host stars, which creates a mini-eclipse and dims the star by a small but detectable amount.

Such a transit lasts only hours and requires exact alignment of star and planet along our line of sight. Kepler will examine thousands of stars to find a few with transiting worlds, said a CfA release.

Once they have found an alien Jupiter, astronomers can look for orbiting moons, or exomoons. Once a moon is found, the next obvious question would be: Does it have an atmosphere?

If it does, those gases will absorb a fraction of the star’s light during the transit, leaving a tiny, telltale fingerprint to the atmosphere’s composition.