Pluto’s climate is out of this world

Written by Alex Deakin, BBC Weather

We know how hard it can be to understand the atmosphere on earth, but maybe we should count ourselves lucky that we are not on the outer extremes of the solar system.

Pluto has always been seen as a bit of an oddball (its classification in the solar system is still an area of debate) and now it seems its atmosphere is pretty extreme too.

Nasa’s New Horizons probe passed by the planet back in 2015, however it is still sending information back to earth and recent research on the data has revealed just how varied the climate on this tiny outpost can be. pluto

It is easy to assume that this small rock on the outskirts of our solar system is just that, a lump of hard, dry rock, but now it seems that liquid nitrogen may have once flowed on the surface and may well do again.

Some parts of Pluto can spend around 50 years in perpetual night.”

The pressure on the earth’s surface is reasonably consistent, usually between around 950 and 1050 hPa (or millibars) but on Pluto it is much lower and much, much more varied. It can range from anything between one hundred thousandth of that on earth to as much as 200 hPa.

Sunlight (or the lack of) is always a big player on any planet’s atmosphere. On earth we think of the arctic zones as extreme when they go several weeks without daylight in the depths of winter, but some parts of Pluto can spend around 50 years in perpetual night.

Graphic showing tilt of Earth compared to PlutoPluto is tilted on its axis by far more than Earth producing more pronounced ‘seasons’

One of the main reasons Pluto’s climate is strange is to do with the tilt. The earth is tilted off its axis by 23 degrees, and it is this slight wonkiness that gives us the seasons. But on Pluto, somewhere that never seems to do things by halves, the tilt is 120 degrees – i.e. it’s north pole actually points downwards! (Though technically its not a ‘north’ pole but the point around which the planet spins anti-clockwise).

It all means the climate on Pluto changes dramatically over millions of years. Although the atmosphere is at a very low pressure at the moment, over time this could increase markedly and the nitrogen on the surface could once again become liquid.

Pluto is a fascinating place with a fascinating atmosphere but I’m glad we don’t have to do the forecast for Plutonian Bank Holidays.