Haze in its atmosphere could make Pluto even colder than expected

Pluto and its atmosphere (Image NASA/JHUAPL/SwRI)
Pluto and its atmosphere (Image NASA/JHUAPL/SwRI)

An article published in the journal “Nature” describes a research on the haze present in the atmosphere of the dwarf planet Pluto’s and its effects on its temperatures. According to a team led by Xi Zhang of the University of California at Santa Cruz, the haze absorb the already low heat from sunlight and emits infrared radiation cooling the atmosphere. That’s the explanation for the fact that NASA’s New Horizons space probe measured a temperature even lower than expected.

During its Pluto flyby on July 14, 2015, the New Horizons space probe carried out a remarkable amount of detections of the characteristics and in particular the composition of the dwarf planet’s atmosphere. On the basis of what was known, scientists had estimated that the temperature on Pluto was around -193° Celsius (-280° Fahrenheit), 100 Kelvin, but the measurements indicated that it was -203° Celsius (-333° Fahrenheit), 70 Kelvin, much colder.

Now this new research offers an explanation to that discrepancy based on the presence of haze, a sort of smog that becomes really dense near the surface. It’s one of the most important elements of Pluto’s atmosphere detected by the New Horizons space probe, and according to this new research is crucial in determining the temperature on the dwarf planet.

The atmosphere of Pluto is composed of several layers: in the upper ones there are chemical reactions caused by ultraviolet radiation coming from the Sun. The ionization of nitrogen and methane generates nanoparticles that have a diameter of some tens of thousandth of millimeter.

Those nanoparticles slowly sink down in the atmosphere and in the meantime they aggregate forming larger and larger particles until they touch the surface. Xi Zhang stated that in his and his collaborators’ opinion those hydrocarbon particles are connected to the reddish and brownish compounds sighted in the images of Pluto’s surface. From this point of view, they agree with previous research.

Despite its distance from the Sun, the effects of the radiation coming from it have their effects on this small world, contributing to making it very alive but in this case also very cold. They make it even more interesting because of the influence of the compounds in the atmosphere. In fact, according to the researchers, this type of study can be extended to moons such as Triton, Neptune’s great moon, and Titan, Saturn’s great moon, and even to exoplanets.

Artist’s impression of Charon seen through Pluto's atmospheric haze (Image courtesy X. Liu)
Artist’s impression of Charon seen through Pluto’s atmospheric haze (Image courtesy X. Liu)

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