Ignorance may feel like bliss, but preparedness offers better odds of surviving what is to come. And when it comes to planetary defense, ignorance just became a bit more inevitable.
Planetary defense is the art of identifying and mitigating threats to Earth from asteroid impacts. And among its tools is planetary radar, an unusual capability that can give scientists a much better look at a nearby object. Arecibo Observatory in Puerto Rico was one of only a couple such systems on the planet, and that instrument’s long tenure is over now after two failed cables made the telescope so unstable that there was no way to even evaluate its status without risking workers’ lives, according to the U.S. National Science Foundation (NSF), which owns the site. Instead, it will be decommissioned.
And when it comes to planetary defense, there’s nothing like it.
“There’s been statements in the media that, ‘Oh we have other systems that can kind of replace what Arecibo is doing,’ and I don’t think that’s true,” Anne Virkki, who leads the planetary radar team at Arecibo Observatory, told Space.com. “It’s not obsolete and it’s not easily replaceable by other existing facilities and instruments.”
Planetary defense begins with spotting as many near-Earth asteroids as possible — nearly 25,000 to date, according to NASA — and estimating their sizes and their orbits around the sun. Arecibo never played a role in discovering asteroids; that task is much more easily completed by a host of telescopes that see large swaths of the sky in visible and infrared light and are able to catch the sudden appearance of a bright, fast-moving dot between the stars, telescopes like the PanSTARRS observatory in Hawaii. With those first observations, the smallest asteroids and those that stay far from Earth can be safely labeled and more or less forgotten.
But larger asteroids with orbits that might bring them too close for comfort get additional study, and often, that work has been Arecibo Observatory’s. The facility sported a powerful radar transmitter that could bounce a beam of light off an object in Earth’s neighborhood. Then, the observatory’s massive radio dish could catch the echo of that signal, letting scientists decipher precise details about an asteroid’s location, size, shape and surface.
The same telescopes that identify asteroids in the first place can also give scientists the data they need to track a space rock’s orbit, but when planetary radar can spot the object, it completes the same work more quickly.
Sometimes that speed will matter, said Bruce Betts, chief scientist at the Planetary Society, a nonprofit space-exploration advocacy group that includes planetary defense among its key issues. “You want to define an orbit as quickly as you can to figure out whether the asteroid is going to hit Earth,” Betts told Space.com.
That’s because with enough warning, humans could theoretically do something to prevent the collision — likely by nudging