Name: 撞擊紐約市的想象中的未來小行星。 (The Imaginary Future Asteroid That Hit NYC)
Uploaded: 2021-01-14T10:30:16.000Z
Duration: 8 min 13 s
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As many a late '90s film suggests, the Earth could be in a bit of trouble

第二類條件句型

if a sufficiently-sized space rock  were to slam into us.

And astronomers around the world are totally on top of it, monitoring potential threats

and developing methods to avert a hypothetical Armageddon.

Which is why last week, a sort of asteroid impact drill was conducted

at the International Academy of Astronautics's annual Planetary Defense Conference,

which demonstrated what might happen if an asteroid hit us within the decade.

Over five days, the conference attendees played out what could happen after the discovery of a hazardous,

but in this case totally fictional, asteroid.

And it demonstrates some of the problems we might face

if we had to tackle  an asteroid threat for real.

NASA's Jet Propulsion Lab created the initial scenario concerning a fictional asteroid dubbed 2019 PDC.

In the real world, JPL's Sentry and the European Space Agency's CLOMON systems

would  calculate the chance of an impact, and refine those estimates over months of monitoring.

But that can get tricky, sometimes an asteroid is too close to the Sun in the sky to observe,

and other times its orbit takes it too far away,

so it's too dim for our dedicated telescopes to pick up.

According to the scenario, it was determined after one month of observation

that 2019 PDC had a 1% chance  of striking the Earth in 2027,

and the asteroid was between 100 and 300 meters across.

A rock that size, with an impact chance of that magnitude,

is listed as a 2 on the Torino Scale  for impact hazards.

Which is a scale that we have, by the way.

But that's mostly because of the relatively low risk.

A three hundred meter asteroid could ravage an entire continent

if it actually hit the Earth in the right spot.

The second day of the conference corresponded to 4 months of theoretical observations,

after which the risk of 2019 PDC's impact  increased to 10%,

and its size was narrowed down to  between 140 to 260 meters.

Analysis of its orbit using computer simulations pinned down where it could possibly hit:

a 70 kilometer wide band stretching from Hawai'i to Africa.

So, the Space Mission Planning Advisory Group, or SMPAG, a real-life group that monitors asteroid threats,

That included two different methods for knocking an asteroid off its current orbit that we could actually use:

a kinetic impactor, which would be a large spacecraft that rams into an asteroid really fast,

If you detonate a nuclear bomb near an asteroid, some of its surface will vaporize,

and it will recoil and hopefully get knocked off its collision course with Earth.

Either way, we'd have to get working pretty soon.

Because we'd have to change the asteroid's orbit before 2025

for the relatively small deflection caused by the blast to actually make 2019 PDC miss the Earth.

And it'll take one to two years for a craft to actually get there.

On top of that, just like our missions to other distant space bodies,

you really only get one launch window a year, if not fewer.

So basically, we'd only have a couple of years to get the plan figured out.

But one problem that would very likely come up in the real world, and did in the fictional scenario,

is that we don't have enough data on the asteroid to know exactly how much we need to deflect it,

and therefore what exactly we need to hit it with.

Rather than just sit and wait over a year for it to get close enough to observe again,

we could send a reconnaissance probe to it.

and it would leave not much wiggle room to analyze that data and then launch the deflector.

It's conference day three now, and we did decide to send a recon craft.

It arrived just before new year's of 2022,

and the extra data from it told us that 2019 PDC  is going to hit Denver.

We were also able to learn more about the rock's makeup.

It appears to be a giant rubble pile, 140 to 220 meters in size.

Based on that, the asteroid would explode 6 to 9 kilometers above the Earth's surface,

creating a blast one hundred times the size of the Tunguska impact back in 1908.

That space rock leveled 2000 square kilometers of uninhabited forest, 80 million trees,

and shattered windows in villages  up to 60 kilometers away.

Only one human reportedly died, but many a reindeer got crispied-up.

To prevent this far worse hypothetical disaster, NASA, the ESA, and the Japanese, Russian,

and Chinese space agencies planned to launch six separate kinetic impactor crafts.

Based on estimates of  the asteroid's mass,

it should only take three such impactors  to nudge it off course.

Which seems smart, since we're talking about losing Denver.

But as a separate backup, NASA could send another recon probe carrying a nuclear device.

There is one problem with that plan, which is that launching a nuke into space

is a violation of  international agreements.

So we'll have to navigate that political problem if it ever comes to it.

But in this scenario, they actually decided against using a nuke.

Day 4 of the conference corresponds to September 2024.

Denver's safe; the kinetic impactors worked,

but chipped off a 50 to 80 meter chunk of the asteroid, and that bit is still headed to Earth.

Perhaps luckily, it's got about a 50% chance of hitting the Atlantic.

Unfortunately, observations are on hold for a few months because the rock is behind the Sun.

with the SMPAG suggesting we use one to break up the fragment into even smaller pieces,

most of which would hopefully burn up in the atmosphere.

On the last day of the conference, corresponding to ten days from impact,

it was announced that a 60 meter fragment will explode 13 to 15 kilometers over Central Park in New York City.

One thousand Hiroshima bombs worth of energy, inflicting serious damage within 33 kilometers.

And none of the attempts in the intervening years had managed to stop it.

Since it's hitting one of the largest cities on the planet,

over ten million people  would need to be evacuated.

And the impact would render the city unlivable, leaving millions without homes even if they survived.

The estimated damage exceeded $70 billion in the local New York and New Jersey area,

which could expand to a loss of over $2 trillion worldwide.

Which was a pretty grim end to the scenario,

although they were able to theoretically prevent  an even worse disaster.

Lucky for us here in actual 2019, there are not any asteroids we've detected  that have

even a 1% chance of hitting us in the next several centuries.