2024-03-29 00:00:44
Composite image of Kuiper belt binary first contact 2014 MU69 from New Horizons Spacecraft Data. Credit: NASA/JHUAPL/SwRI/Roman Tkachenko
Research challenges established views on Kuiper belt objects, revealing their ability to retain much more volatile ice than previously thought, thus offering new perspectives on comet evolution.
An article recently published in the journal Icarus presents findings on the Kuiper Belt 486958 Arrokoth, and sheds new light on the preservation of volatiles such as carbon monoxide (CO) in such distant celestial bodies.
The paper “Ice and CO2 Gas Preservation within 486958 Arrokoth” written by Dr. Samuel Birch of Brown University and SETI Institute Senior Scientist Dr. Orkan Omorhan uses Arrokoth as a case study to suggest that many Kuiper Belt Objects (KBOs) – Relics from the dawn of our solar system – could still retain their original volatile ice, challenging previous conceptions of the evolutionary path of these ancient entities.
The left image was taken by the Multi-Color Imaging Camera (MVIC), part of the RALPH instrument aboard New Horizons. Taken on January 1, 2019, just 7 minutes before closest approach, the spacecraft was only about 6,700 km from the surface. Credit for this incredible capture goes to NASA, the Johns Hopkins University Applied Physics Laboratory and the Research Institute of the Southwest. The right image shows the average temperature in the orbit at the seasonal skin depth of Arrokoth, calculated based on the method of Umurhan et al. from 2022. The scale is in kilometers, and the view direction is similar to the image on the left, looking down towards the South Pole. Credit: NASA, Johns Hopkins University Applied Physics Laboratory and Southwest Research Institute
Challenging past models
Previous models of KBO evolution needed help predicting the fate of volatiles in these cold, distant objects. Many relied on clumsy simulations or flawed assumptions, underestimating how long these materials could last. The new research suggests a simpler but effective approach, comparing the process to how gas escapes through porous rock. This suggests that KBOs like Arrokoth can retain their volatile ice for billions of years, creating a sort of underground atmosphere that slows further ice loss.
“I want to emphasize that the main thing is that we have corrected a deep error in the physical model that people have assumed for decades for these old cold objects,” O’Moorhan said. “This study could be the initial impetus for re-evaluating the comet’s internal evolution and activity theory.”
Our model includes a porous debris pile, consisting of a mixture of CO and refractory amorphous ice H2O, with specific pore radii ????????. The top layer, described by heat, is thermally processed in only one pass, resulting in the loss of CO (both ice and gas) in this layer. Below the sublimation front ????????, shown in dark blue, the original CO ice volume remains intact. Over time, as the sublimation front moves downward (to the right in the model), CO ice embedded in the amorphous H2O ice matrix begins to sublimate. The produced gas, marked in light blue, fills the pores and moves upwards, away from the sublimation front. Credit: SETI Institute
New insights and future investigations
This research challenges the existing predictions and opens new avenues for understanding the nature of comets and their origins. The presence of such volatile ice in KBOs supports a fascinating narrative of these objects as “ice bombs”, which activate and exhibit cometary behavior after changing their orbit closer to the Sun.
This hypothesis could help explain phenomena such as the intense burst activity of comet 29P/Schwassmann-Wachmann, which could change the understanding of comets.
As co-investigators for the upcoming CAESAR mission proposal, the researchers are taking a new approach to understanding the evolution and activity of cometary bodies. This research has implications for future research and is a reminder of the ongoing mysteries of our solar system, waiting to be revealed.
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