How large an asteroid could a person jump off?

Asteroid 243 Ida.NASA/JPL
Asteroid 243 Ida and its small moon.

This interesting question goes back to 1952 or even earlier. It turns out that the asteroid must be no bigger than 3.9 v(ρe / ρ) kilometers in diameter, where ρ is the asteroid’s density and ρe is that of Earth in the same units (S&T: July 1984, page 62). Given how poorly we know the densities of asteroids, about all we can say is that the object can be up to 4 km across if it’s as dense as our planet, or perhaps 9 km if it’s a “rubble pile.”

So a human could easily hop the 1.5-km span from 5381 Sekhmet to its moon and back, since both bodies are 1 km or less in size. The astronaut might even jump from 243 Ida’s tiny moon, Dactyl, all the way to Ida itself, 90 km away — taking care not to miss!

—Roger W. Sinnott


Image of Alexander


July 10, 2020 at 9:48 am

The answer also depends on the astronaut's jumping ability. Is she a typical great grandmother? Or is he a toddler, or an NBA guy at his prime?

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