MCQ Detailed View

Pluto’s atmosphere is very different from Earth’s. It is thin and primarily composed of nitrogen (N₂), with smaller amounts of methane (CH₄) and carbon monoxide (CO). Unlike Earth, Pluto cannot hold a permanent atmosphere because of its small size and low gravity. Its atmospheric behavior depends strongly on its distance from the Sun during its long elliptical orbit of 248 years.

When Pluto is closer to the Sun, solar heat is enough to warm the icy surface and cause sublimation of nitrogen and methane ices. These gases rise and form a thin but detectable atmosphere. However, as Pluto moves farther away from the Sun in its orbit, the surface temperature drops drastically, often below –220°C. At these extreme cold conditions, the gases that formed its atmosphere begin to condense and freeze back onto the surface as ice.

This means that Pluto’s atmosphere is not stable like Earth’s but seasonal and temporary. Scientists describe it as a “freezing and thawing” cycle of gases. When near perihelion (closest point to the Sun), the atmosphere grows thicker due to sublimation. When Pluto heads toward aphelion (farthest point from the Sun), the atmosphere collapses and freezes directly onto the ground.

The incorrect options do not describe this process accurately. The atmosphere is not absent, because frozen gases remain on the surface. It does not turn into plasma, as plasma requires extremely high temperatures. The option “volatile” is partially related, but the correct and precise description is that the atmosphere becomes frozen.

Thus, as Pluto moves farther from the Sun, its nitrogen and methane atmosphere freezes onto the surface, creating a cycle of atmospheric collapse and reformation.