Here's How Many Years in Advance We'd Need to Stop a Killer Asteroid Coming For Earth

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Here's How Many Years in Advance We'd Need to Stop a Killer Asteroid 
Coming For Earth

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MORGAN MCFALL-JOHNSEN & AYLIN WOODWARD, BUSINESS INSIDER
13 MAY 2021

Last month, experts from NASA and other space agencies around the world 
faced a troubling hypothetical scenario: A mysterious asteroid had just 
been discovered 35 million miles away, and it was heading for Earth. The 
space rock was expected to hit in six months.

The situation was fictional, part of a week-long exercise that simulated 
an incoming asteroid in order to help US and international experts 
practice how to respond to such a situation.

The simulation taught the group a difficult lesson: If an Earth-bound 
asteroid were spotted with that little warning, there's nothing anyone 
could do to keep it from hitting the planet.

The experts determined that no existing technologies could stop the 
asteroid from striking, given the scenario's six-month window. There 
isn't a spacecraft capable of destroying an asteroid or pushing it off 
its path that could get off the ground and fly to the rock in that 
amount of time.

Paul Chodas, manager of NASA's Center for Near-Earth Object Studies, 
helped host the recent simulation, as well as five previous ones like 
it. He said this exercise set the participants up for failure.

"It's what we call a short-warning scenario," he told Insider. "It was, 
by design, very challenging."

In reality, if an asteroid like that fictional one were heading for 
Earth, scientists would need years – not months – of warning. Five years 
is the minimum, according to Chodas. Others, like MIT astronomer Richard 
Binzel, say we'd need at least a decade.

"Time is the most valuable commodity you could possibly wish for, if 
faced with a real asteroid threat," Binzel told Insider.

But scientists haven't identified most of the hazardous space rocks that 
pass near our planet, which makes the chances slim that we'd get a five- 
or 10-year warning period. In 2005, Congress attempted to address this 
issue by mandating that NASA find and track 90% of all near-Earth 
objects 140 meters (460 feet) or larger. At that size, asteroids could 
obliterate a city the size of New York. But to date, NASA has only 
spotted about 40% of those objects.

"What that means is, for now, we are relying on luck to keep us safe 
from major asteroid impacts," Binzel said. "But luck is not a plan."

To defend a planet, 'know thy enemy'

In NASA's recent simulation, the participating scientists didn't know 
how big the hypothetical asteroid was until a week before it was set to 
hit Earth.

"We didn't know if the object was 35 meters across or 500 meters across. 
And that makes a very big difference," Sarah Sonnett, a researcher at 
the Planetary Science Institute who participated in the exercise, told 
Insider.

A 35-meter asteroid could explode in the atmosphere and send shockwaves 
through a neighborhood. A 500-meter asteroid could decimate a city, 
affecting an area the size of France.

So a crucial part of stopping an asteroid from hitting Earth is 
understanding as much as possible about the rock. That includes its 
size, the path it takes around the sun, and what it's made of. With that 
information, scientists can evaluate strategies to dismantle the rock or 
disrupt its path.

"It takes time to know thy enemy," Binzel said.

Ideally, Sonnett said, scientists would be able to study a hazardous 
asteroid as it passed Earth a few times in its orbit around the sun, 
before that path brought it close enough to collide with our planet. 
Observing a passing asteroid several times could take years or even decades.

Step 2: Destroy or deflect the asteroid
NASA has three main tools in its planetary-defense arsenal. The first is 
to detonate an explosive device near an oncoming asteroid to break it up 
into smaller, less dangerous chunks. The second is to fire lasers that 
could heat up and vaporize the space rock enough to change its orbital 
path. The third is to send a spacecraft to slam into the asteroid, 
knocking it off its trajectory.

NASA is about to test that last strategy. Its Double Asteroid 
Redirection Test will send a probe to the asteroid Dimorphos in the fall 
of 2022 and purposefully hit it.

But any of the three options, Chodas said, would take years.

"Typically, that's a drawn-out, multi-year process to go from proposal 
to actually having a spacecraft on a launch vehicle – let alone the fact 
that you still have to cruise to get to your destination and deflect the 
asteroid," he said.

After that, it would take one or two years for the asteroid's path 
around the sun to actually change enough to carry it away from Earth. 
That's why the timeline matters: The earlier scientists can identify a 
hazardous space rock, the less ambitious a deflection mission would have 
to be.

But of course, all of these methods are useless if nobody knows the 
asteroid is coming.

"I think the best investment is in knowledge. The best investment is 
knowing what's out there," Binzel said.

That means completing a catalogue of near-Earth objects that could 
damage the Earth.

NASA is developing a space telescope to track asteroids

NASA is planning a mission to track down asteroids that are too dim for 
telescopes on Earth to see. The NEO Surveyor Mission, as it's known (NEO 
stands for near-Earth object), would launch an infrared telescope into 
Earth's orbit in 2026. Sonnet is on that mission team.

"If we do the job now of finding those objects and tracking them, 
knowing their orbits, knowing where they're going to head, and then 
characterizing their sizes, then we should be in really good shape," she 
said.

If the telescope launches and works as planned, it should fulfill NASA's 
Congressional mandate to find 90% of the most dangerous near-Earth objects.

But for five years, the NEO Surveyor has been caught in "NASA mission 
limbo hell," as Binzel put it. Due to insufficient funding, it hasn't 
moved past the early development phase.

Sonnett has her fingers crossed that the NEO Surveyor Mission will do 
well in an upcoming review. At the end of this month, NASA will assess 
whether the mission is ready to move into the next phase. If so, the 
team could start building prototypes and developing hardware and 
software. If not, the telescope's launch could be delayed even further.

"Because we now have the capability to detect and know what is out 
there, I think scientifically we have a moral responsibility to obtain 
that information," Binzel said. "It would be unconscionable that we were 
caught by surprise, by an asteroid impact that we could have seen coming."

This article was originally published by Business Insider.