Whipple suggests that comets have large, solid nuclei consisting of conglomerates of ices--such as water, ammonia, methane, carbon dioxide, and carbon monoxide--mixed with meteoritic dust
. According to Whipple's model, as an icy nucleus reaches perihelion (its closest approach to the Sun), solar radiation heats up the body's frozen gases, forming the coma and, in some cases, a long, beautiful tail.
In their earlier study of the distribution of the meteoritic dust
They also collected soil samples contaminated with meteoritic dust
. Based on those findings, the initial mass of the interplanetary intruder was estimated to be at least 70 tons.
They come from cosmic dust, meteoritic dust
and cometary dust.
In his Fifty Year Canon of Lunar Eclipses: 1986-2035, Fred Espenak speculates that the enlargement might be caused by sunlight passing through a layer of meteoritic dust
suspended 120 to 150 kilometers high in the Earth's atmosphere.
"Geochemists have concluded," writes Flerov, "that these rocks contain a considerable amount of meteoritic dust
produced as a result of sputtering of a hypothetical cosmic body that had undergone a collision with the earth."