There's a giant, peanut-shaped
object orbiting the Sun,
and its name is Halley’s comet.
Like all comets,
it’s a cosmic mash-up of frozen ice,
gases, and dust.
Stretching a vast 15 km by 8 km (9 mi by 5 mi),
this space snowball
streaks by Earth every 76 years.
It hasn’t caused us any trouble yet,
but that would change if its elliptical return
crosses paths with our Moon,
causing a devastating collision
visible in broad daylight.
It’s the year 2061,
and crowds are gathering to watch the impending fireworks.
We would have known about the impact
for a while because of the predictability
of the comet’s orbit,
and although a scary event,
it would be a sight to behold.
The explosion would be
similar to the 2013 collision
of an asteroid into the Moon
which created an eight second light show
and left a 40 m (131 ft) wide crater.
So instead of merely leaving a crater,
Halley’s comet would rip the Moon’s surface apart.
From the Earth,
this would look equal parts beautiful and terrifying.
But on the Moon, it would just be pure terror.
Magma from the core of the Moon would spill out,
shooting large plumes of dust
and material into space.
Particles and smaller debris would be harmless
and float around the Moon,
but heftier chunks would gain enough speed
to escape the gravity of the Moon and enter space.
Once in space,
they would travel toward Earth,
pulled by our planet’s gravity.
"It's meteors. Take evasive action."
Hopefully we would have enough time to prepare,
because at this point,
people would need to shelter in
underground bunkers
as fire rains down from above.
The last time a large rock
exploded in our atmosphere was in 2013.
Chelyabinsk was a 19 meter (62.3 ft) wide meteorite,
and its explosion was equal to
half a million tons of TNT.
If any fallout from the Moon
was similar in size to Chelyabinsk,
whole cities could be destroyed.
Eventually, we’d get the all clear
to leave our bunkers.
Some places would only be
moderately damaged,
while others would be completely demolished.
Rebuilding would begin,
but the effects of Halley’s comet
crashing into our Moon would be far from over.
Our dreams of continuing
space exploration would be dashed.
We would need the Moon as a pit stop
to restock and refuel for exploring space.
But because of severe damage from the comet collision,
landing there would be difficult,
if not impossible.
So any thoughts of mining the Moon
for the essential raw materials to advance
space technology wouldn't fly.
At the very least NASA and
other space agencies would become
better funded.
The world would rely on them
to keep constant track of the dangerous
Moon chunks still left in our orbit.
And if you’re speculating all the dust
and debris would give Earth
a beautiful ring like Saturn’s,
well, better luck next time.
Or maybe not.
Because for a ring to form around the Earth,
we’d need an even mightier collision.
That's a story for another What IF.