[Vn_survivor_67-68]

Why would a comet suddenly “explode” just before impact?

further, why would a comet choose to “explode” and leave a layer of soot across N America like one would expect with a full eruption of Yellowstone?

just asking, LOL

[blam]

"further, why would a comet choose to “explode” and leave a layer of soot across N America like one would expect with a full eruption of Yellowstone?"

When Yellowstone erupts it leaves a six foot deep ash layer as far away as Nebraska. You know, little things like that. (Ahem)

It exploded for the same reason the Tunguska Event did in 1908.

[Psycho_Bunny]

If the speed, angle of entry and mass of a comet are just right, it'll explode before hitting the ground.  It happens fairly often.

[Domestic Church]

Why would a comet suddenly explode just before impact?

Picture an enormous celestial mudball with mixed densities hitting the pressurized atmosphere.

[ridesthemiles]

Why would a comet suddenly “explode” just before impact?”

Suicide Comet???

[GingisK]

Why would a comet suddenly “explode” just before impact?

Rapid heating caused by friction with the atmosphere. Very common for "falling rocks".

[SunkenCiv]

Comets don’t choose to do that, they aren’t animate (IMHO). Heating due to passage through the atmosphere during terminal descent causes smaller objects to bust apart and, yes, explode above the impact site. That’s what happened in 1908 above Tunguska. Very large objects don’t generally fall apart during descent, unless they’re already fragments which had wound up stuck together during their long sojourn around the Sun.

[Red Badger]

Why would a comet suddenly “explode” just before impact?

For the same reason an egg will explode if you put it in the microwave?...............

[Kozak]

Why would a comet suddenly “explode” just before impact?

Ever hear of Tunguska? The short answer is the build up of heat and aerodynamic forces as the object enters the lower atmosphere.