Scientists including one of Indian origin believe that aliens might be wandering within our solar system but we simply are missing them because we have not looked closely enough at outer space.
The White House this week issued a statement saying there was no existing evidence that aliens had attempted to contact earth - or in fact that they even existed.
But two researchers at Penn State university disagree with the Obama administration, and insisted that our deep-space probes – NASA’s Pioneer and Voyager craft - may be equally too small for extraterrestrial civilisations to notice.
Their paper on the subject has been accepted by Acta Astronautica and posted online on ArXiv.
Jacob Haqq-Misra, of Rock Ethics Institute, and Ravi Kumar Kopparapu, of the Earth and Environmental Systems Institute, claimed alien spacecraft or probes the size of a racing yacht could be floating around our solar system, and we’re blissfully unaware.
"The vastness of space, combined with our limited searches to date, implies that any remote unpiloted exploratory probes of extraterrestrial origin would likely remain unnoticed," the Daily Mail quoted them as writing.
"Extraterrestrial artifacts may exist in the solar system without our knowledge, simply because we have not yet searched sufficiently. Few if any of the attempts would be capable of detecting a one- to ten-metre probe.
"Searches to date of the solar system are sufficiently incomplete that we cannot rule out the possibility that non-terrestrial artifacts are present and may even be observing us.
"The completeness of our search for non-terrestrial objects will inevitably increase as we continue to explore the moon, Mars and other nearby regions of space," the researchers concluded.