Aliens may have travelled to Earth already without us noticing, according to a NASA scientist.
Silvano P Colombano, a computer scientist at NASA Ames Research Centre, says humans may not have even noticed the extraterrestrials arrival on earth due to the vastly different looks.
Colombano says the aliens could have arrived to the planet in the form of something other than carbon-based organisms – meaning they would go undetected.
In a research paper, he wrote: “I simply want to point out the fact that the intelligence we might find and that might choose to find us (if it hasn’t already) might not be at all produced by carbon-based organisms like us.
“The size of the ‘explorer’ might be that of an extremely tiny super-intelligent entity, reports The Independent.
“If we adopt a new set of assumptions about what forms of higher intelligence and technology we might find, some of those phenomena might fit specific hypotheses, and we could start some serious enquiry.”
Colombano also says it is worth re-considering what civilization may look like across the universe.
He said scientists should “consider further that technological development in our civilisation started only about 10,000 years ago and has seen the rise of scientific methodologies only in the past 500 years”.
He added that because of this as humans may have a “real problem predicting technological evolution even for the next thousand years, let alone six million times that amount.”
Scientist Dr Maggie Aderin-Pocock also said extraterrestrial life could look very different than expected.
Basing her theory on how life began on Earth, she believes the mutants would be large marine-type animals with metallic skins and orange backsides.
They would suck chemicals from the atmosphere and communicate using pulses of light along their spines.