In 2012, astronaut Ron Garan did an AMA on Reddit. In between questions about aliens (he didn’t see any in space) and where his coffee came from (recycled urine), he responded to a question about why we should accept the risks of a future mission to Mars. Garan quoted a colleague: “If the dinosaurs had a space program, they’d still be here.”

Putting aside the unlikelihood of giant reptiles with brains the size of walnuts developing their version of Apollo 11, the point here is that the dinosaurs were almost certainly wiped out by a nearly 6-mile-wide asteroid that struck the Earth with the destructive power of billions of Hiroshima-scale nuclear bombs, causing an “impact winter” that cut off sunlight and led to drastic cooling far beyond what most dinosaurs could survive.

The dinosaurs, of course, could do nothing about the killer asteroid, other than presumably waving their tiny arms at the oncoming doom. But if they did have a space program — and yes, now I’m imagining a T. rex in a space suit, swaggering to a rocket like John Glenn in The Right Stuff — they might have been able to detect that incoming asteroid decades in advance, and done something to avert their doom.

Humans, though, are in a better place — as shown by the recent news over an asteroid called 2024 YR4 that briefly appeared to be threatening the Earth.

Killer asteroids, briefly explained

The Chicxulub asteroid that likely wiped out the dinosaurs wasn’t the first time a massive asteroid collided with the Earth. An asteroid 12 to 16 miles wide hit the planet more than 2 billion years ago, in what is now Vredefort, South Africa, while another 6 to 10 miles wide hit what is now Sudbury, Ontario 1.85 billion years ago. More recently, a 130-foot-wide space rock exploded 6 miles above Siberia in 1908, creating........

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