NASA has among its ranks countless asteroids listed as potential threats to Earth.
Space rocks across our Solar System and the Universe at large are currently whizzing through space at breakneck speed, some on a collision course with our home.
Luckily for us, the space agency has been working on industry-breaking technology that will enable it to detect threatening objects in space and redirect them out of harm’s way.
However, it recently emerged that there are asteroids that NASA knows about but cannot see.
Thousands of so-called “invisible” asteroids are floating around space, hiding behind the sun’s blinding rays, with scientists unable to spot them even at the last minute.
The perfect example of this came just ten years ago, on February 15, 2013, in the city of Chelyabinsk, Russia.
Back then, a meteor the size of a semi-trailer shot out of the direction of the rising sun and exploded over the city.
For a time it glowed brighter than the sun itself and exploded with 30 times more energy than the bomb that destroyed Hiroshima.
The blast shattered windows on more than 7,000 buildings, temporarily blinded scientists, inflicted ultraviolet burns on many people and injured a further 1,600.
While no deaths occurred, scientists were extremely worried about how they had missed this colossus of rock from hurtling towards Earth and smashing into its surface.
“The most problematic object is the one you don’t know about,” Amy Mainzer, a professor of planetary science at the University of Arizona and principal investigator for two NASA asteroid-hunting missions, told Live Science. “If we can know what’s out there, then we can have a much better estimate of the true risk.”
Events like that seen in Chelyabinsk are extremely rare and rocks like the meteor that hit it breach Earth’s atmosphere once every 50 to 100 years, according to estimates from the European Space Agency (ESA).
This doesn’t stop the threat and the occasional anomaly which hides in the sun’s wake.
At any given moment, the sun obscures countless asteroids from view, including a constantly rotating cast of Apollo asteroids, objects near to the Earth that spend most of their time beyond Earth’s orbit but have the ability to cross our path.
Dr Scott Sheppard, a staff scientist at the Carnegie Institution for Science, said: “Aten asteroids are the most dangerous because they cross Earth’s orbit just barely at their most distant point.
“You would never see one coming, to some degree, because they’re never in the darkness of the night sky.”
The majority of these hidden space rocks are more than likely small enough to disappear completely in the Earth’s atmosphere due to burning up.
But it’s estimated that there are many undiscovered asteroids measuring more than 460 feet in diameter, large enough to cause localised chaos on impact.
Described as “city killers”, Prof Mainzer believes the team have found around 40 percent of those asteroids in the 140-meter neighbourhood.
But this leaves 14,000 yet to be found, and there could be far bigger objects lurking in the sun’s glare.
A handful of “planet killer” asteroids — which measure more than 3,280 feet in diameter and are capable of stirring enough dust to spark a global extinction event — could well lurk in the sun’s glare, according to Dr Sheppard.
Last year, he and his team found one such planet killer obscured by the sun, and say they’re “definitely several more kilometre-size” asteroids out there waiting to be found.
The best way for scientists to do this is by entering space itself. Several telescopes currently orbit the Earth and are free from the distorting and blinding effects of the sun to spot rogue asteroids.
Infrared imaging can detect the heat of such rocks to help researchers spot their wayward paths.
There’s only one infrared telescope in space right now, the Near-Earth Object Wide-field Infrared Survey Explorer, or NEOWISE, launched in 2009 and designed to detect objects far from Earth.
In 2013, after the Chelyabinsk incident, NEOWISE was injected with new software and a new mission to search for invisible Earth-shattering objects.