Astronomy
The Composition and Origins of Cometary Nuclei
Quick fact
Cometary nuclei are often compared to 'dirty snowballs,' but they are actually darker than charcoal because their surface is covered with complex organic compounds and dust, not pure ice.
Why this is interesting
When you see a comet streaking across the sky, you're looking at the remnant of a building block from the birth of our solar system—but the glowing tail is not the comet itself. What exactly is that icy heart, and where did it come from?