Aliens could be using asteroids to spy on us, scientists have said.
Since 1984, the Search for Extraterrestrial Intelligence (SETI) has been scouring the sky, hoping to eavesdrop on conversations between alien civilisations.
But now a SETI scientist says that aliens might have been listening to us all along.
James Benford, a physicist and independent SETI researcher says that if an advanced extraterrestrial species was interested in us, their best plan would be to monitor us using tiny probes on co-orbitals.
Co-orbitals are the half-dozen or so small asteroids that share the Earth’s orbit around the Sun.
Cruithne, for example, a 5km rock discovered in 1986, orbits the Sun at roughly the same distance as the Earth, crossing its orbit twice a year.
“These near-Earth objects provide an ideal way to watch our world from a secure natural object,” theorises Dr Benford.
“That provides resources an ETI might need: materials, a firm anchor, and concealment.”
“Meanwhile, it could have been routinely reporting back on our biosphere and civilisation for long eras.”
And it’s just the kind of place that a curious alien race might park a monitoring station. Or, better still, an interstellar “phone box’ that we could use to call the aliens up.
“A probe located nearby could bide its time while our civilisation developed technology that could find it, and, once contacted, could undertake a conversation in real time,” Dr Benford says in a new paper.
He points out that, despite being so close, they remain virtually unexplored.
He said: “These have been little studied by astronomy and not at all by the Search for Extraterrestrial Intelligence (SETI) or planetary radar observations.
“We should move forthrightly toward observing them, both by observing them in the electromagnetic spectrum and planetary radar, as well as visiting them with probes.”
“If we don’t find anything, that means no one has come to look at the life of Earth for over billions of years,” Dr Benford said. “That is a big surprise, a stunning thing.”
But not everyone agrees.
“How likely is it that [an] alien probe would be on one of these co-orbitals? Obviously, extremely unlikely,” theoretical physicist and astrobiologist Paul Davies from Arizona State University, told Live Science.
“But if it costs very little to go take a look, why not? Even if we don’t find E.T., we might find something of interest.”
China has already announced plans to launch a probe to survey one of our near-neighbours, the catchily-named 2016 HO3.
That probe, to be launched in 2022, will stop off at 2016 HO3 (also known as Kamo’oalewa) to collect samples.
It will then drop the samples off on Earth before continuing on its way to rendezvous with 133P/Elst-Pizarro, an enigmatic Solar System body that is a rare hybrid between an asteroid and a comet.
Even the smallest hint of an alien probe would completely revolutionise our understanding of science, but even without that, samples of water ice from the earliest moments of the Solar System’s existence will shed important light on how we came to be here, alone in the Universe.