Newly analyzed observations suggest particles are mostly frozen nitrogen
Clouds in Pluto’s atmosphere may be composed of tiny frozen spherules of nitrogen or carbon monoxide, rather than snowflake-like clumps of tiny particles as previous research had suggested, new analyses suggest.
Information about Pluto’s atmosphere is, like that atmosphere itself, exceedingly thin because no space probes have yet visited there. So most speculations about the dwarf planet’s atmosphere stem from analyses of light passing through that tenuous shroud on the rare occasions when Pluto passes in front of a distant star, says Pascal Rannou, a planetary scientist at the University of Reims in France.
The dwarf planet’s tenuous atmosphere contains suspended particles, not just gas. Previous research suggested that those aerosols are about 200 nanometers across — larger than expected and therefore probably raspberry-like clumps or snowflake-like aggregates of tiny particles that had frozen together when they collided aloft, he notes.