Imagine our Solar System as a big neighborhood.
At the far end of it, just past Neptune’s orbit, lies a massive icy zone known as the Kuiper Belt.
This area is packed with icy objects, including the dwarf planet Pluto. One of the most exciting things about these Kuiper Belt Objects (KBOs) is their incredible variety of colors, from pure white to dark reddish hues.
For a long time, scientists didn’t know why KBOs were so colorful. Some thought it might have to do with the high amount of radiation these icy bodies get exposed to from cosmic rays.
And it turns out, they were right!
A group of researchers from the University of Hawaiʻi at Mānoa, led by Professor Ralf I. Kaiser, has found the answer to this color mystery.
They shared their results in the Science Advances journal on May 31.
To solve this puzzle, they replicated the conditions of the Kuiper Belt right here on Earth.
They exposed hydrocarbons (organic molecules made from hydrogen and carbon atoms), such as methane and acetylene, to high radiation levels, similar to what they would experience in the Kuiper Belt.
What did they discover? Specific organic molecules – including phenanthrene, phenalene, and acenaphthylene – which are kind of like little chemical building blocks with up to three rings, turned out to play a crucial role in giving KBOs their reddish colors.
The research also showed how complex these cosmic ray interactions with hydrocarbons can be and hinted at their potential role in creating precursors for life.
Kaiser said this research was an important beginning to understand the true reasons behind the diversity of colors in the Kuiper Belt. Notably, other chemicals like ammonia, water, and methanol have also been found on KBOs.
So, further studies into how these ices react to cosmic rays might give us an even better understanding of what causes the amazing array of colors seen in the Kuiper Belt.
This research team was not just from Hawaiʻi. It included scientists from Côte d’Azur University in France, Southwest Research Institute in Colorado, and UCLA, showing that solving space mysteries is an international effort.
So, the next time you look up at the night sky, remember – there’s a lot more color out there than you can see!
