SOLAR SYSTEM

Detailed explanation-1: -Comets are collections of rocky material and ices, sometimes referred to as “dirty snowballs”. One of their key features is their large abundance of so-called “volatile” compounds, things like carbon dioxide, water and noble gases that sublimate (change from solid to gas) very easily.

Detailed explanation-2: -Comets are sometimes called dirty snowballs or “icy mudballs". They are a mixture of ices (both water and frozen gases) and dust that for some reason didn’t get incorporated into planets when the solar system was formed. This makes them very interesting as samples of the early history of the solar system.

Detailed explanation-3: -Comets are loosely packed dirty snowballs, formed of various ices (i.e. water, carbon dioxide, methane, ammonia, carbon monoxide, and cyanide/cyanogen) as well as dirt and rocks.

Detailed explanation-4: -In the 1990s astronomers recognized that Pluto, which has a diameter of about 2, 300 km (1, 400 miles), is a giant icy leftover from the time when the planets formed. Pluto had been classified as a planet from its discovery in 1930 but was reclassified as a dwarf planet in 2006.