This is how we save the earth from hidden death asteroids

Mysterious asteroids in the blind spot

Asteroids the size of the Chelyabinsk meteorite, with a diameter of about 20 meters, enter the atmosphere every 50 to 100 years, according to an estimate by the European Space Agency, ESA. Larger asteroids are more rare.

So far, astronomers have mapped the orbits of more than 33,000 near-Earth asteroids, but none of them pose a risk to our planet in the next century.

But astronomers cannot calculate the risk of an asteroid they cannot see. And according to the scientists, there are countless of them, including some that are so big that they can destroy cities or the entire earth if they are not detected in time.

Some of them belong to the so-called Apollo asteroids. These are near-Earth objects that spend most of their time far outside the Earth’s orbit, but occasionally cross the planet’s orbit on their way to the Sun.

Another group is the mysterious class of asteroids called Atens, which orbit almost entirely close to Earth, but always on the dayside of the planet, where they are hidden from telescopes.

“Aten asteroids are the most dangerous because they cross Earth’s orbit exactly where they are furthest away,” Scott Sheppard, an astronomer at the Carnegie Institution for Science, told Live Science. “You will never spot them in time, partly because they are never in the darkness of the night sky.”

Scientists fear hidden ‘planet killers’

Most hidden space objects are likely to be so small that they will burn up when they enter Earth’s atmosphere.

However, the researchers also expect that there are many undiscovered asteroids with a diameter of over 140 metres. That makes them large enough to travel through the atmosphere and destroy entire cities if they hit the Earth’s surface, Amy Mainzer explains to LiveScience. She is a professor at the University of Arizona and has led two of NASA’s asteroid hunts.

“We think we have found around 40 percent of the hidden asteroids at a height of 140 metres,” says Mainzer. According to Nasa’s estimates, there are around 14,000 left to find.

Much larger objects can also be hidden in the sun’s glare. Although extremely rare, there can be a handful of “planet killers” – asteroids more than one kilometer in diameter capable of stirring up enough dust to trigger a global mass extinction.

However, the size of the “planet killers” also makes them easier to detect in time.

Two new telescopes must protect the earth

Looking for asteroids near the Sun is a difficult challenge for astronomers. Most space telescopes look towards the night side of the planet to avoid both solar glare and radiation damage.

And telescopes on Earth have even greater limitations because the sun has to be in just the right position for them, giving them only half an hour to look for the hidden space rocks, explains Scott Sheppard.

Astronomers therefore put their trust in infrared space telescopes.

“Only a small part of an asteroid’s surface is illuminated by the sun, even in space,” Luca Conversi, head of ESA’s Coordination Center for Near-Earth Objects (NEOs), told Live Science. “So instead of looking at the sunlight reflected off the surface, infrared telescopes look at the asteroid’s own heat radiation, so we can find it.”

Currently, there is only one infrared space telescope actively looking for near-Earth asteroids – the Near-Earth Object Wide-field Infrared Survey Explorer, or NEOWISE. But the telescope cannot see close enough to the Sun, so the mission will end in July 2024, explains Amy Mainzer.

Instead, two new space probes will help keep an eye on the sun’s blind spot. Nasa is scheduled to launch NEO Surveyor in 2027, and ESA’s NEOMIR will, if all goes well, be ready to keep an eye on the sun from 2030, says Conversi.

Both spacecraft will be equipped with infrared detectors and high solar shields that will make it possible to look for asteroids very close to the Sun.

NEO Surveyor will scan the entire sky every two weeks, dividing its attention equally between each side of the sun, says Mainzer, who has led the projects for both NEOWISE and NEO Surveyor. The telescope is primarily expected to detect near-Earth objects with a width of 50 to 100 metres.

NEOMIR will scan a ring-shaped area around the Sun every six hours. According to the researchers, the two new lookouts will ensure that we are not surprised by a space rock the size of the Chelyabinsk meteorite again.

“According to our forecasts, NEOMIR would have detected the Chelyabinsk meteorite about a week before the collision,” says Conversi. “More than enough time to warn the population and implement safety measures.”