Hopes of finding evidence of life on far off alien worlds by studying their atmospheric chemistry have been dashed by a new study that concludes it’s almost impossible.

The study from the University of Toronto finds the method used to detect biosignatures on exoplanets can produce a false positive result.

The presence of multiple chemicals such as methane and oxygen in an exoplanet’s atmosphere is considered an example of evidence of past or present life. Rein’s team discovered that a lifeless planet with a lifeless moon can mimic the same results as a planet with such a biosignature.

“You wouldn’t be able to distinguish between them because they are so far away that you would see both in one spectrum,” Rein commented.

The resolution needed to identify a genuine biosignature from a false positive would be impossible to obtain even with telescopes available in the foreseeable future, he said.

Rein added: “A telescope would need to be unrealistically large, something one hundred metres in size, and it would have to be built in space. This telescope does not exist, and there are no plans to build one anytime soon.”

Current methods can estimate the size and temperature of an exoplanet in order to determine whether liquid water could exist on the its surface, one of the criteria for a planet hosting the right conditions for life.

Many researchers use modelling to imagine the atmosphere of these planets, but they still can’t make conclusive observations, said Rein. “We can’t get an idea of what the atmosphere is actually like, not with the methods we have at our disposal.”

To date, 1,774 exoplanets have been confirmed to exist, and there could be more than 100 billion planets in the Milky Way galaxy alone. Despite the results, Rein is optimistic the search for life on planets outside our own is possible if done the right way.

“There are plenty of reasons to be optimistic that we will find hints of extraterrestrial life within the next few decades, just maybe not on an Earth-like planet around a Sun-like star.”

Source: https://goo.gl/SnwTB4.