Are exoplanets mimicking signs of life when there is none?

Are astronomers being fooled by signs of life on exoplanets? This may well be the case if we believe a significant research, suggesting that the search for life on planets outside our solar system may be more difficult than previously thought.

The presence of multiple chemicals such as methane and oxygen in an exoplanet's atmosphere is considered an example of a biosignature, or evidence of past or present life.

The researchers at University of Toronto Scarborough (UTSC) discovered that a lifeless planet with a lifeless moon can mimic the same results as a planet with a biosignature.

"You would not be able to distinguish between them because they are so far away that you would see both in one spectrum," said Hanno Rein, an assistant professor from department of physical and environmental science at UTSC.

To properly identify a genuine biosignature from a false positive would be impossible to obtain even with telescopes available in the foreseeable future, Rein emphasised.

"A telescope would need to be unrealistically large, something 100 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 any time soon," he noted.

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

According to the new study, astronomers can not get an idea of what the atmosphere is actually like with the methods that have at their disposal.

There are 1,774 confirmed exoplanets known to exist, but 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.

The search for life within our solar system should remain a priority.

"Be optimistic that we will find hints of extraterrestrial life within next few decades, just maybe not on an earth-like planet around a sun-like star," the study said.