A rare asteroid flyby will happen soon, but NASA may be left on the sidelines

Though NASA is certain that the asteroid poses no risk, at least for this upcoming flyby, it's fun to think about how things would go if it did indeed strike. Apophis is roughly 450 meters across and weighs around 30 million metric tons (though i've seen conflicting numbers on its mass), and is moving at over 30km per second. That's a gargantuan amount of kinetic energy.

If the asteroid were to strike, let's say somewhere on one of the continents, the resulting destruction would be similar to the simultaneous detonation of at least a few thousand nuclear bombs minus the particle radiation..... but with so much more impact energy.

This would generate a near-instant super-heated, molten crater at least 15km across and immediately followed by a hypersonic blast wave that would utterly annihilate everything within a radius of at least a couple hundred kilometers. The even faster-traveling thermal pulse in between those two would flash-fry any flammable thing out to maybe twice the distance of the blast wave, and even at the outer edge of said thermal pulse, this includes causing lethal, almost total third to fourth-degree burns over any living tissue.

It would not be a good day for the people of whatever wider region that surrounds its impact point.

Globally, we'd also see atmospheric effects. They'd be nothing like the ones that struck the dinosaurs down into near total extinction, but they'd be noticeable, and would cause social, economic and environmental havoc. It would maybe be comparable to something like the 1815 Tambora eruption, whose climatic effects basically killed summer for much of the world in that year. Only here it would happen in modern times and from a much scarier type of disaster, hammering delicate modern infrastructure and communications.

If Apophis struck somewhere fairly densely populated, like, say, the Eastern U.S, almost anywhere in Europe or somewhere in central to Eastern China, in just seconds we'd have close to the biggest human death toll from a natural disaster in all our history, and the second-order effects of it would kill millions to tens of millions more. I can only think of the Black Death or maybe the 1918 flu pandemic as candidates for worse, albeit much slower killing.

If Apophis were to hit the ocean, things get a bit harder to estimate and guesstimate.

On the one hand, it's "only" 450 meters across, and much of the ocean is damn deep, enough so as to swallow the asteroid whole and mitigate much of its more fiery atmospheric effects. On the other hand all that kinetic energy still has to go somewhere, and so in this case, perhaps creates a massive ocean-spanning series of tsunamis that hit thousands of kilometers of coastline with waves big enough to drown tens of millions of people.

Then again, maybe the word drown doesn't quite describe it. More accurately these waves would be pulverizing, smashing the victims in their way into surrounding objects with enough force to cause catastrophic tissue and bone trauma. Millions would be smashed to death much much faster than they could drown. In a way, it would be something of a mercy.

Fun stuff.

From https://science.nasa.gov/solar-system/asteroids/apophis/

> Near-Earth asteroid Apophis is a potentially hazardous asteroid that will safely pass close to Earth on April 13, 2029. It will come about 20,000 miles (32,000 kilometers) from our planet’s surface — closer than the distance of many satellites in geosynchronous orbit (about 22,236 miles, or 36,000 kilometers, in altitude).

> When Apophis was discovered in 2004, it appeared the asteroid could potentially impact Earth in the coming decades. Astronomers closely tracked the asteroid, and now NASA is confident that there is no risk of Apophis impacting our planet for at least 100 years.