Asteroid which whizzed past Earth exposes ‘blind spot’ in our planetary defence

Near-Earth asteroid, computer artwork.
Is there a 'blind spot' in our asteroid defence? (Getty)

Astronomers have warned that an asteroid that whizzed past Earth harmlessly last week has highlighted a blind spot in our ability to spot dangerous space rocks.

A NASA expert has warned that the visit from 2023 BU, a small space rock that streaked by 2,200 miles from the Earth's surface, closer than some satellites highlights the fact that little is done to track smaller asteroid.

Terik Daly, a planetary scientist at the Johns Hopkins Applied Physics Laboratory, "We don't know where most of the asteroids are that can cause local to regional devastation.

"How many natural hazards are there that we could actually do something about and prevent for a billion dollars? There's not many.”

Read more: Scientists warn dangerous space rocks could be hiding in meteor shower

NASA for years has prioritised detecting asteroids much bigger and more existentially threatening than 2023 BU.

It closely tracks such ‘near Earth objects’ and there’s no way a ‘doomsday’ asteroid could sneak up on our planet.

"Very few of these bodies are potential hazards to Earth, but the more we know and understand about them, the better prepared we will be to take appropriate measures if one is heading our way," NASA said.

2023 BU sits on the smaller end of a size group, asteroids five to 50-metres in diameter, that also includes those as big as an Olympic swimming pool.

Objects that size are difficult to detect until they wander much closer to Earth, complicating any efforts to brace for one that could impact a populated area.

A five-metre rock is estimated to target Earth once a year, and a 50-metre rock once every 1,000 years, according to NASA.

Smaller rocks, like the asteroid that exploded over Chelyabinsk in Russia in 2013, will hit our planet every 10 to 100 years, experts say.

Read more: Huge meteor explodes in the sky above Derby

The asteroid which ‘blew up’ over the Russian town of Chelyabinsk in 2013, is thought to have been around 60 feet across.

During the 2013 Chelyabinsk event, 1500 people were injured and 7300 buildings damaged by the intense overpressure generated by the shockwave at Earth’s surface.

No-one saw it coming before it entered Earth's atmosphere.

The roughly 20-metre meteor that exploded in 2013 over Chelyabinsk, Russia is a once-every-100-years event, according to NASA's Jet Propulsion Laboratory.

Some astronomers consider relying only on statistical probabilities and estimates of asteroid populations an unnecessary risk, when improvements could be made to NASA's ability to detect them.

One major upgrade to NASA's detection arsenal will be NEO Surveyor, a $1.2bn telescope under development that will launch nearly a million miles from Earth and surveil a wide field of asteroids.

It promises a significant advantage over today's ground-based telescopes that are hindered by daytime light and Earth's atmosphere.

That new telescope will help NASA meet a goal assigned by Congress in 2005: detect 90% of the total expected amount of asteroids bigger than 140 meters, or those big enough to destroy anything from a region to an entire continent.

"With Surveyor, we're really focusing on finding the one asteroid that could cause a really bad day for a lot of people," said Amy Mainzer, NEO Surveyor principal investigator.

"But we're also tasked with getting good statistics on the smaller objects, down to about the size of the Chelyabinsk object."

Asteroid detection gained greater importance last year after NASA slammed a refrigerator-sized spacecraft into an asteroid to test its ability to knock a potentially hazardous space rock off a collision course with Earth.

The successful demonstration, called the Double Asteroid Redirection Test (DART), affirmed for the first time a method of planetary defence.

"NEO Surveyor is of the utmost importance, especially now that we know from DART that we really can do something about it," Daly said.

"So by golly, we gotta find these asteroids."

Watch: NASA says incoming asteroid will have close encounter with Earth