The monstrous asteroid, dubbed Asteroid 2018 VW, is expected to make its closest approach early this afternoon.
NASA’s astronomers at the Jet Propulsion Laboratory (JPL) in California expect a flyby around 2.16pm GMT (UTC).
Just six hours later, around 8.04pm GMT, a second and much smaller asteroid will swing by the planet.
The first of the two space rocks, Asteroid VW, is estimated to measure anywhere between 154.2ft and 360.89ft (47m and 110m).
At 360.89ft, the asteroid stands taller than Big Ben’s Elizabeth clock tower in London’s Westminster and is about the same height as St Paul’s cathedral.
In other words, the asteroid’s diameter is roughly the equivalent of 10 double-decker buses lined up in a row.
And even at the smaller end of the estimate, the asteroid is a formidable and potentially destructive space rock.
At 154.2ft, Asteroid VW is about as tall as the Arc de Triomphe in Paris and is nearly as tall as Nelson’s Column in Trafalgar Square.
Any asteroid measuring upwards of 65.6ft (20m) has the potential to injure thousands of people if it strikes in a residential area.
The 2013 Chelyabinsk meteor incident, which injured 1,500 people with shattered glass, is believed to have been caused by a 65.6ft-wide (20m) space rock exploding over the Russian city of Chelyabinsk.
Professor Stephen Nelson of Tulane University, South Florida, explained: “Although the Chelyabinsk meteorite probably weighed about 12,000–13,000 metric tonnes, and measured 17 to 20m in diameter before it exploded, scientists were quick to point out that it was very small compared to other objects that could potentially hit the earth.
“The explosion released energy estimated at about 500 kilotons of TNT – about 20 to 30 times more energy than the Hiroshima atomic bomb.
“The event brought to the world’s attention the very real hazards associated with the impact of objects from outer space.”
Thankfully neither of the two asteroids flying by today will come within striking distance of the planet.
Although the US space agency NASA warned the space rocks will make a Close Earth Approach, the asteroids will still be hundreds of thousands or millions of miles away from Earth at their closest.
Asteroid VW is expected to pass Earth from a distance of about 0.03948 astronomical units (au) or 3.67 million miles (5.9 million km).
The distance is equivalent to more than 15-times the distance between the Earth and the Moon.
The second asteroid, dubbed Asteroid 2018 VN1, will zip by from a slightly closer distance of 0.02224au.
This means the asteroid will flyby from more than 2.06 million miles (3.32 million km) or 8.66-times the distance from Earth to the Moon.
NASA said: “As they orbit the Sun, Near-Earth Objects can occasionally approach close to Earth.
“Note that a ‘close’ passage astronomically can be very far away in human terms: millions or even tens of millions of kilometres.”