Assertion: comet's material | /r/HasProperty | heavy elements
Facets:
Source sentences:
text: Because they formed far from the Sun, these bodies have little refractory material (heavy elements with high melting and vaporization points, such as iron, nickel, silver, gold, platinum, etc.); they are instead made up mostly of lighter substances with lower vaporization temperatures: oxygen, carbon, silicon, hydrogen-rich compounds.