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From preliminary findings of habitable planets to the eyebrow-raising suggestion that an visiting cosmic object might not be as it appears, the possibility of extraterrestrial existence has long tantalised researchers and citizens. But experts say ET is more likely to be found if we look in our immediate cosmic vicinity.

The Enceladus Discovery

The prospect was revitalised when researchers revealed the probability increased that Saturn's sixth largest moon could support life after a study found it is spewing out a broader range of carbon-based substances than previously known.

"I really like Enceladus because it has all the conditions that are co-located at the right moment for organisms to develop and to thrive," said the research scientist.

Perfect Environment

As well as sophisticated carbon compounds and a substantial water body of liquid water, scientists note that the Saturn's satellite is thought to have thermal vents – providing a source of energy – with the chemical balance of the water within parameters considered appropriate for life.

Difficulties in Distant World Studies

Although scientists should continue to seek organisms outside our planetary system, this method presents difficulties – not least that it depends on identifying molecular markers in a planet's atmosphere that could be associated with life.

"It has to change the whole planet so that you are capable of detecting it on an distant planet," she said. "In other words, local pockets of life that do not create these large-scale changes might be overlooked."

And there is a further challenge: "You cannot look for past life on an exoplanet," the scientist noted.

Detection Limitations

What's more, an exoplanet must pass in front of its star for instruments to analyse its atmosphere. And although preliminary data is found, it can be challenging to understand or verify.

"The problem regarding distant planets is that we have limited knowledge about the surroundings," commented a different specialist.

Benefits of Nearby Investigation

By contrast, local celestial objects like Enceladus, which sits 1.27bn km from Earth, can be examined directly.

Space agencies are developing expeditions to the Saturn moon, with researchers developing equipment to look for molecules on the Saturnine moon.

Other Candidates

However, it isn't the sole location beyond Earth where organisms might exist in our solar system. Including other promising candidates is Europa, another planetary satellite that – similar to Saturn's moon – is thought to have an sea below its icy crust.

"To me, in the solar system, that's where we will discover organisms," the researcher stated.

Supportive Studies

Scientists are eager to stress it is not a case of examining nearby worlds rather than exoplanets, but rather that the approaches support one another, with the solar system acting as a "natural laboratory" for collecting information.

This can be used to test theories and create simulations that can enhance comprehension of the potential habitability of the different categories of planet discovered by distant world studies.

"I believe looking in our own back yard is a win-win situation," said a planetary researcher, adding Enceladus is a prime example of a object displaying all the indicators of potential life that scientists are also looking for in exoplanets.

Future Implications

"Should we find that there are truly indications of life [on Enceladus] that enhances the pursuit outside our solar system even more exciting," he said.

"Should we travel and find that regardless of favorable factors for habitability, we fail to detect any evidence of organisms it indicates that we may require to rethink the definition of habitability or at least reevaluate the probability of life emerging on a possibly life-supporting planet."

Wider Significance

The scientist indicated studying neighbouring bodies could have consequences regarding the potential of organisms elsewhere.

"The fascinating aspect is that if we find life anywhere else in the solar system ... it signifies that it's not random," she said. "This indicates it's widespread in the Milky Way."