A brand new study is shaking up what scientists thought they knew about distant objects within the far reaches of the solar system, starting with an object called the space snowman.
Researchers from Brown University and the SETI Institute found that the double-lobed object, which is officially named Kuiper Belt Object 486958 Arrokoth and resembles a snowman, can have ancient ices stored deep inside it from when the thing first formed billions of years ago. But that is only the start of their findings.
Using a brand new model they developed to review how comets evolve, the researchers suggest this feat of perseverance is not unique to Arrokoth but that many objects from the Kuiper Belt — which lies on the outermost regions of the solar system and dates back to the early formation of the solar system around 4.6 billion years ago — can also contain the traditional ices they formed with.
“We have shown here in our work, with a moderately easy mathematical model, that you may keep these primitive ices locked deep throughout the interiors of those objects for really long times,” said Sam Birch, a planetary scientist at Brown and certainly one of the paper’s co-authors. “Most of our community had thought that these ices must be long lost, but we expect now that will not be the case.”
Birch describes the work within the journal Icarus with co-author Orkan Umurhan, a senior research scientist on the SETI Institute.
Until now, scientists had a tough time determining what happens to ices on these space rocks over time. The study challenges widely used thermal evolutionary models which have didn’t account for the longevity of ices which might be as temperature sensitive as carbon monoxide. The model the researchers created for the study accounts for this alteration and suggests that the highly volatile ices in these objects stick around for much longer than was previously thought.
“We’re mainly saying that Arrokoth is so super cold that for more ice to sublimate — or go directly from solid to a gas, skipping the liquid phase inside it — that the gas it sublimates into first has to have travel outwards through its porous, sponge-like interior,” Birch said. “The trick is that to maneuver the gas, you furthermore may should sublimate the ice, so what you get is a domino effect: it gets colder inside Arrokoth, less ice sublimates, less gas moves, it gets even colder, and so forth. Eventually, every little thing just effectively shuts off, and also you’re left with an object stuffed with gas that’s just slowly trickling out.”
The work suggests that Kuiper Belt objects can act as dormant “ice bombs,” preserving volatile gases inside their interiors for billions of years until orbital shifts bring them closer to the sun and the warmth makes them unstable. This latest idea could help explain why these icy objects from the Kuiper Belt erupt so violently after they first catch up with to the sun. Unexpectedly, the cold gas inside them rapidly gets pressurized and these objects evolve into comets.
“The important thing thing is that we corrected a deep error within the physical model people had been assuming for a long time for these very cold and old objects,” said Umurhan, Birch’s co-author on the paper. “This study might be the initial mover for reevaluating the comet interior evolution and activity theory.”
Altogether, the study challenges existing predictions and opens up latest avenues for understanding the character of comets and their origins. Birch and Umurhan are co-investigators in NASA’s Comet Astrobiology Exploration Sample Return (CAESAR) mission to amass at the least 80 grams of surface material from the comet 67P/Churyumov-Gerasimenko and return it to Earth for evaluation.
The outcomes from this study could help guide CAESAR’s exploration and sampling strategies, helping to deepen our understanding of cometary evolution and activity.
“There may perhaps be massive reservoirs of those primitive materials locked away in small bodies all across the outer solar system — materials which might be just waiting to erupt for us to watch them or sit in deep freeze until we are able to retrieve them and convey them home to Earth,” Birch said.
