November 21, 2011 - The White House this week issued a assertion saying there was no current evidence that aliens had attempted to get in touch with earth - or in truth that they even existed.
But how can the Obama administration be so sure?
The question is being asked by researchers, who say that we have not seemed carefully sufficient at outer space - and that there could be big alien greetings indicators in the solar system that we simply are missing.
And they include that our deep-space probes - Nasa's Pioneer and Voyager craft - might be equally also small for extraterrestrial civilisations to observe.
Probing the neighbours: The twin Voyager 1 and Voyager 2 probes, launched in the Seventies, have thorough info about Earth and humanity, just in case they are recovered by alien explorers
The White House was responding to an inquiry as part of the 'We The People' project, which permits members of the public to submit petitions requesting govt action.
One petition asked for a formal acknowledgment of 'an extraterrestrial presence partaking the human race'.
Phil Larson, who works on policy and communications for the White House's Office of Science & Technologies Policy, replied: 'The U.S. federal government has no evidence that any life exists outside our planet, or that an extraterrestrial presence has contacted or engaged any member of the human race.'
But two researchers at Penn State university beg to vary, and their paper on the subject matter has been acknowledged by Acta Astronautica and posted online on ArXiv.
The Appears Of Earth: The 'Golden Records' accompanying the Voyager probes have recordings and detailed binary data about the solar system (hopefully, alien civilisations have not yet invented CDs)
Jacob Haqq-Misra, of Rock Ethics Institute, and Ravi Kumar Kopparapu, of the Earth and Environmental Systems Institute, say alien spacecraft or probes the measurement of a racing yacht could be floating close to our solar system, and we're blissfully unaware.