Life on Earth has already been subjected to a number of mass extinctions throughout its
history.
The world-ending events of the past have brought everything from volcanic eruption to slow-build
climate change to fundamental changes in the makeup of our atmosphere.
An asteroid strike, though, brings much more sudden death and destruction, as well as all
of those other factors.
So, could a rock from space one day trigger our next mass extinction?
This is Unveiled and today we’re uncovering the extraordinary asteroids that could one
day kill us all.
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Though large asteroid strikes are a rare occurrence, smaller ones happen far more frequently.
According to NASA, Earth is bombarded with an average of 100 tons of space dust on a
daily basis, and small asteroids (which are still roughly the same size as small cars)
enter Earth’s atmosphere every year.
Thankfully, the vast majority of rocks like these burn up before they hit the ground…
but, occasionally, our planet is pelted with something bigger.
The amount of damage a larger asteroid could cause depends on a variety of factors including
the speed and angle of impact, but even were an asteroid with a width of just twenty-five
meters to land in a rural and unpopulated area, it’s thought the force would still
be enough to shatter windows and release light bright enough to cause instant sunburn.
A rock the size of a house could detonate on Earth with as much power as a nuclear bomb.
Meanwhile, asteroids the size of football fields impact on Earth roughly every 2,000
years.
However, for an asteroid to truly threaten the entire planet, it has to have a diameter
of at least one kilometre.
Fortunately, rocks this size ramming into us are exceptionally rare, but that’s not
to say that the solar system as a whole doesn’t contain thousands of asteroids big enough
to pose a problem.
In fact, a width of one kilometre is actually quite small compared to some of what’s lurking
in the Asteroid Belt, for example, where rocks can be as large as nine hundred Kilometres
across, and more.
As far as we know, we’ve never been hit with anything quite that big, but arguably
the most famous asteroid strike in history came via the Chicxulub Impactor some sixty-six
million years ago.
A fateful rock thought to have been more than ten kilometres across, it’s also held by
many as the event which triggered the K-Pg mass extinction which wiped out the dinosaurs.
There’s no real reason to expect another impact on this scale any time soon, but such
monumental events do happen - and could theoretically happen at any moment were an asteroid to go
unnoticed.
Missing something that big, though…
Does it ever really happen?
Surprisingly, yes, it does.
In the summer of 2019, for example, we had a reasonably close call with an asteroid named
2019 OK - a football-field-sized rock which flew right by Earth with little to no warning
beforehand.
2019 OK came within 70,000 kilometres of our planet, meaning it was less than one-fifth
the distance to the moon from us.
Still a long way away, but cosmologically speaking uncomfortably nearby.
In fact, it was the largest asteroid to pass by Earth in a century, and yet it was only
spotted on the very same day that it flew past us.
Say 2019 OK had veered just a fraction off course and headed towards Earth…
It would have made an impact that devasted an area at least 80 kilometres across.
Generally speaking, NASA and the world’s other space agencies are on top of things,
however, keeping track of thousands of asteroids flying through space at any given time.
Sure, there are some that slip through, but for the most part we’re already well aware
of the most threatening asteroids out there, and we’ve calculated the likelihood that
they’ll ever cross our path.
Prior warning; asteroid naming practices aren’t exactly what you’d call “creative”…
One of the most threatening to us is named “(85713) 1998 SS 49”.
This particular asteroid is part of the Apollo group, a band of asteroids that are all expected
to pass close by Earth at multiple times in the future, with this one expected to also
eventually pass closer than the moon at around 344,000 kilometres.
While it’s smaller than the Chicxulub Impactor at around three kilometres wide, were it to
veer off course and hit us then it would still inflict major damage.
Interestingly, “(85713) 1998 SS 49” is also expected to pass by both Mars and Venus,
making it a multi-planet threat - although so far there’s no solid evidence that a
collision will happen.
It’s difficult to precisely track objects like these because of their low reflectivity
and relatively small size compared to things like planets and moons… but these asteroids
are also listed as PHAs (Potentially Hazardous Asteroids) for a reason; because researchers
believe they have the potential to change direction to become even more threatening
than they already are.
No matter how tricky it is to keep rocks like these in our sights, scientists are doing
everything they can not to lose them!
Another asteroid listed as a PHA is 4179 Toutatis, one of the largest and most lethal objects
currently expected to pass close by Earth.
With a diameter of five kilometres, it’s more than big enough to end a large majority
of life and trigger worldwide effects on our planet if it strikes.
Toutatis is especially notorious, though, because it has a highly eccentric orbit, meaning
that it’s also one of the most unpredictable asteroids out there.
It’s also a frequent visitor to our particular region of the solar system, having had various
close encounters with Earth - including in 2012, when it passed within eighteen lunar
distances of us.
It’s currently projected to pass by Earth again in 2069, but this time it will be twice
as close….
If that projection proves correct, then we’ll be comfortably safe… but if its orbit proves
even more chaotic than we think it is, then maybe not!
The outright largest known asteroid with the potential to impact Earth is another prospect
entirely.
It’s named “(53319) 1999 JM 8” - and is a whopping seven kilometres wide, making
it only slightly smaller than the asteroid that wiped out the dinosaurs.
It’s another frequent flier around these parts, having passed within 0.2 astronomical
units of Earth at least five times in the last century - with its next approach at a
similar distance slated for 2075.
JM 8 is also extremely dim, has exceptionally low reflectivity and a chaotic orbital path,
all of which makes it especially difficult to track through a telescope and therefore
a likely candidate for one day passing by without our knowing.
In the event that it didn’t pass by but instead smashed into us… well, our planet
would be plunged into an apocalyptic scenario, facing multiple extinctions and total ecological
shakeup.
But - and this is important - not one of these asteroids is actually expected to hit Earth;
rather to pass unusually close by.
Right now, their orbits are subject to change, which is why they’re monitored as a potential
threat… but that doesn’t mean that any of these rocks really will crash into us anytime
soon.
It’s just that if any of them did change course, defy predictions and make straight
for us, then they’d all have the potential to bring about worldwide chaos.
And those are the asteroids that could kill us all.
What do you think?
Is there anything we missed?
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