# Would a direct hit by a small comet be catastrophic?

Would a direct hit by a short-period comet with a 3 mile diameter nucleus cause enough damage on Earth to threaten or destroy human life and the ability to produce crops?

Here, have some fun with this...

http://impact.ese.ic.ac.uk/ImpactEffects/

It doesn't go into long term effects, but the short term is pretty devastating for a significant portion of the planet. 'Nuclear winter' effects seem inevitable for those not atomised, scorched, crushed, or covered in ejecta.

Not good, nope.

• Excellent answer. I’m voting up. The recommended website provides rough approximation (it should suffice) of how people, infrastructure etc. are affected. You should type in there “Distance from impact” that is the distance from the place a comet hits. You may vary the amount of devastation by the comet diameter (projectile diameter). There will be good descriptions. And don’t forget to set the density of comet to 0.5 (one cubic meter weighs around 500 kg though the approximation is so rough that is not critical anyway). Hope all the fuss in the previous thread etc. didn’t confuse you.
– user18491
Commented Sep 18, 2017 at 6:14
• So you may tailor devastation by setting different “projectile diameter” values or its speed. The typical speed for a comet is around 50 km per second and it is all indicated there. The faster the speed the more devastation :) Also don’t forget my new link “more visual and user-friendly update to our impact calculator, developed and hosted by Purdue University” from the previous thread (purdue.edu/impactearth)
– user18491
Commented Sep 18, 2017 at 6:23
• unless the nucleus happens to be very low density,which is a possibility. I'd hazard a guess that total mass is more important than raw diameter Commented Sep 18, 2017 at 13:05
• Yes, GBowman, Ken Draco, and Carl Witthoft - the impact calculator website was an amazing source of variables. I tested a wide array of sizes, density of projectile and target, distance from impact, and more. you've all been a tremendous help. Commented Sep 18, 2017 at 23:04