Near-Earth Asteroids: Why Thousands Of Space Rocks Still Remain Undetected

Just recently, astronomers at NASA spotted an asteroid that whizzed past our planet a few hours after being spotted. The space rock was as big as a warehouse (155-330 feet across) and approached Earth at just half the distance to the moon.

The sheer size and speed of the asteroid, at 66,000 miles per hour, could have meant catastrophic consequences for our planet, had it been on a collision course. Though nothing happened in this case, many wonder how many of these near-Earth objects (NEOs), exists in our neighborhood and why it is so late that we detect them, at least in some cases.

Technically, the term NEO means a space object that comes within 30 million miles of our planet. There are millions of these objects in our neighborhood and every now and then one gets closer than the distance between the Earth and Moon, close by astronomical standards.

The International Asteroid Warning Network — a UN-sanctioned organization — includes NASA and other space agencies and is a global project on asteroid identification and tracking.

But, if we look from the perspective of size, considering objects like the one that flew past us last weekend or bigger than that, the data comes down to a few thousand asteroids. These objects are the real threat and could leave a catastrophic impact on Earth if not detected in time.

NASA astronomers have detected some 8,000 asteroids spanning at least 460 feet across, but approximately 17,000 similar ones still remain undetected, Space.com reported. The risk further increases from some 50 more that go beyond 3000 feet in diameter (as big as a mountain), that are still undiscovered.

This means, most of the biggest NEOs are cataloged, but there is still a long way to go for the medium-sized ones.

Identifying and tracking these many asteroids is a real challenge to the space agency. But it is not that nobody wants to do it. It’s just that it gets really difficult to observe objects like these in visual wavelength, especially when they are small or medium-sized and dim.

As, Live Science reported, the chemical composition of some asteroids makes them less reflective to be observed from ground based optical telescopes. Plus, being close to us, near earth objects move very quickly in the sky which means telescopes also have to be pointed at the right direction at the right time.

NASA's Planetary Defense Coordination Office currently uses a large network of telescopes to scan the sky at once, but the agency has also stressed the need to bolster that effort.

Back in September 2017, a NASA study noted that ground-based telescopes were not enough to scan all corners of the sky, and they needed to place a large telescope, at least 1.6 feet wide, and a wide-field camera in space to conduct infrared observation to identify the objects in question.

The mission, dubbed Near-Earth Object Camera or NEOCam, is already in the works, but there is no word on when it might take to the skies. Scientists at NASA hope it will identify all 17,000 of the undiscovered asteroids within a decade and characterize their physical properties, so that appropriate action can be taken if one is on an Earth-threatening route.

Speaking of action, it is also worth noting NASA is working on a mission called Double Asteroid Redirection Test (DART), to deflect incoming asteroids. The mission will launch in 2020 and is expected to be tested in 2022 on the 500 feet wide moon of an asteroid called Didymos. The idea of pulling an asteroid out of its orbit via gravitational forces was also posited but that mission didn’t get the required White House funding.