Pluto, the dwarf planet inhabiting our solar system’s outer reaches, has been intriguing the scientific community for a long time. However, NASA’s New Horizons historic flyby in 2015 changed everything, it gave us our first close-up look at the mysterious system that mankind could see, and they were not disappointing.
The visuals revealed Pluto’s stunning terrain, including a broad swath of maroon patch that sweeps around the planet’s equator the Cthulhu Macula, which is a non-icy landscape on an otherwise remarkably icy body. The bright, maroon/red regions were earlier thought to be caused by molecules known as tholins. These are organic compounds which rain down onto the surface after cosmic rays or ultraviolet light interact with the methane present onPluto’s surface and atmosphere.
However, new study suggests that there’s more to the dwarf planet’s maroon-coloured deposits than known earlier. According to a new study published in the journal Icarus, hints to tholins alone may not be the only cause for the red swathes on the celestial body.
To analyse further, a team of researchers led by aerospace engineer Marie Fayolle of the Delft University of Technology in the Netherlands created tholins in their laboratory. The emphasis of their study was to compare the way they reflect light against the observations of the dwarf planet and they found that the spectral signatures don’t quite match up.
Fayolla’s team recreated Pluto’s atmosphere in a chamber and then blasted them with plasma to simulate the irradiation in space. It resulted in a low-density cloud of atmospheric gases that reacted with the plasma by condensing into dust-like particles. It produced synthesised tholins, which were submillimeter-sized spherical particles that the researcher team could shine light on to evaluate the reflections against the light bouncing off Pluto, as detected by New Horizons.
While the experiment didn’t match the observed conditions on Pluto, the researchers have hypothesised several potential causes to investigate in future research. Among the findings, they suggest space radiation may be darkening the Cthulhu Macula and changing the way it absorbs light. Another possibility points that the texture of Pluto’s surface is more porous than expected. A third possibility may be due to the planet’s weak gravity, as it may create a thin layer of tholins, resulting in a fluffy, porous crust.
“From reconstructed reflectance spectra and direct comparison with New Horizons data, some of these tholins are shown to reproduce the photometric level (i.e. reflectance continuum) reasonably well in the near-infrared," the journal/report further cited the researchers’ new study.
More research and experiments are needed to pin down the exact cause of Pluto’s red plains, meanwhile the team is planning future experiments to better understand how the planet’s surface interacts with its atmosphere.