A trio of Harvard scientists claim that UFO sightings could point to a hidden community of aliens electing to conceal themselves on Earth.

Despite no extraterrestrial life ever being conclusively detected, it doesn’t mean aliens can’t exist.

Early attempts to search for other lifeforms within our galaxy began in the mid-20th century and just last year Nasa officials announced it would be taking ‘concrete action’ to shift the ET conversation from ‘sensationalist to science’.

There may well be more life dwelling within our realm - but new research claims the aliens are one step ahead on the finding front.

A paper published on ResearchGate by Tim Lomas, Brendan Case and Michael Paul Masters claims ‘intelligent beings [are] concealed in stealth here on Earth’.

This scientific thesis, published earlier this month, is titled: A case for scientific openness to a concealed earthly explanation for Unidentified Anomalous Phenomena.

The trio claims in the paper that public interest and attention regarding Unidentified Anomalous Phemonemona (UAP) or Unidentified Flying Objects (UFOs) has increased over the past few years.

“Hypotheses for such phenomena tend to fall into two classes,” they write.

“A conventional terrestrial explanation (e.g., human-made technology), or an extraterrestrial explanation (i.e., advanced civilizations from elsewhere in the cosmos).”

Their belief is that there is a ‘third minority class of hypothesis’ - an unconventional terrestrial explanation.

It’s outlined in this third explanation of UFO citings that extra-terrestrial life is ‘walking among us’ disguised as human beings.

The study also claims these alien lifeforms, who have previously arrived from another planet, could be convening in underground bunkers or perhaps converging on the Moon.

Researchers who worked on the paper agree that this idea is ‘likely to be regarded sceptically by most scientists’ but they argue that their ideas should not be dismissed.

Instead, they ask fellow space researchers to ponder their hypothesis and begin to calculate whether crypoterrestrials could really be hidden on Earth.

"It may be exceedingly improbable, but hopefully this paper has shown it should nevertheless be kept on the table as we seek to understand the ongoing empirical mystery of UAP," concludes the study.

Earlier this month, Nasa pleaded with European-based space scientists to begin collaborating on a mission to Uranus.

The call comes after data from the Voyager-2 probe in 1986 collected data that suggested two of the planet’s moons could have active oceans.

If this information is correct, then it could indicate extra-terrestrial life.

Therefore, Nasa want to probe further and put a robotic spacecraft into Uranus’ orbit.

The proposed mission is expected to take around ten years to develop and to make sure it stays within the correct time frame, Nasa wants to form a partnership with the European Space Agency (Esa).

The plea was made in the leading science journal, Nature.