Our solar system is home to millions of renegade space rocks, and this week three particularly large ones will blast past Earth. But don’t worry—the closest will still miss our planet by a comfortable 2.2 million miles (3.5 million kilometers), or about 10 times the average distance between Earth and the moon, according to NASA.
Monday (27 February) an asteroid named 2012 DK31 will sail past our planet at a distance of about 3 million miles (4.8 million km). The asteroid measures an estimated 450 feet (137 meters) across, or about as wide as a 40-story skyscraper is tall, and its orbit around the Sun crosses Earth’s orbit every few years.
Although the space rock poses no imminent threat to Earth, NASA classifies it as a Potentially Hazardous Asteroid (PHA) – meaning the rock is large enough and orbits close enough to Earth that it could cause serious damage if its orbit changes and a collision occurs . Generally, any asteroid measuring more than 450 feet across and orbiting within 4.6 million miles (7.5 million km) of Earth is considered a PHA. (NASA has mapped this asteroid’s orbit for the next 200 years, and no collisions are predicted).
Related: Could an asteroid destroy the Earth?
On Tuesday (February 28), another skyscraper-sized PHA, also measuring about 450 feet across, will cross the planet’s orbit at a distance of about 3.5 million km. Known as 2006 BE55this thick space rock’s orbit crosses Earth’s orbit every four or five years.
Finally, on Friday (March 3), an asteroid measuring about 250 feet (76 m) will fly by at a distance of 3.3 million miles (5.3 million km). The stone, is called 2021 QWis not quite wide enough to qualify as a PHA, but still approaches Earth every few years.
Why do scientists pay so close attention to space rocks that will miss our planet by millions of miles? Because even small changes in an asteroid’s orbit—for example, from being nudged by another asteroid or affected by the gravity of a planet—can send nearby objects like these on a direct collision course with Earth.
Fortunately, NASA calculations show that no known asteroids are currently on track to hit Earth for at least 100 years. Should a large asteroid one day pose a direct threat to our planet, astronomers are already working on methods to prevent it. That was the motivation behind NASA’s latest Double Asteroid Redirection Test (DART) mission, who intentionally smashed a rocket into an asteroid to alter its orbital velocity. The mission did not destroy the target directly, but proved that missile strikes are capable of directly changing a space rock’s trajectory parameters in significant ways.