Of all the planets in the solar system, Saturn has by far the most satellites. This says a lot. Sure, we’re with our single friend the Moon™, but Neptune roams the universe with 16 known companions, Uranus has 28 companions of its own, and Jupiter has as many as 95 nearby moons. But what about Saturn? It’s a different league. This ring world has 146 these natural satellites. However, you might be surprised to learn that even with such lovely Saturn options, scientists mostly focus on just one of them.
So when studying Enceladus, every detail matters — which brings us to a new, very strange detail that scientists are focusing on: The ice-capped moon has a strange, disappearing dark patch point. No one knows what it is yet, but it might tell us something about those plumes that could house the precious building blocks of life we seek.
The dark spot was one of the interesting topics discussed during the 2024 American Geophysical Union meeting in Washington, D.C., where scientists gathered to find the last piece of the cosmic puzzle they have been working on solving all year.
The room was filled with awe when Cynthia B. Phillips, a planetary geologist at NASA’s Jet Propulsion Laboratory, introduced the study, detailing how she and her team originally identified the black spots. That’s thanks to her crewmate, Leah Sacks, who helped dig into the vast amount of data NASA has collected about Enceladus. Voyager and Cassini Task. The purpose of the analysis is to compare images taken by these spacecraft of the same area to identify any changes to the lunar surface.
Possible changes could reveal fascinating information about the world’s geological activity, but we’ll get to that shortly; first let’s dig into the mysteries of black spots.
“After looking at dozens of pairs of images, she noticed something interesting,” Phillips said during the meeting. “It was a small black spot; about a kilometer in diameter. She spotted it in a photo in 2009 and looked at it again in 2012 and it seemed to have disappeared.”
On the left, black spots can be seen. When it reaches the middle, it seems to disappear. (Image credit: DA Patthoff You are )
As the years go by, the dark spots slowly disappear, become smaller, and never become more noticeable. How strange, especially since Enceladus has what’s called a high “albedo.” This basically means that the world is really bright – so it would be completely unexpected to find a dark spot on it, let alone a disappearing dark spot. But before getting too excited, scientists make sure to second-guess themselves as much as possible to rule out obvious warnings.
“The first question we have is,” Phillips said, “is it just that we don’t see it in some low-resolution images, but it’s there?” In short, the answer is a simple “no,” probably not. For example, a direct comparison of the 2010 and 2011 images shows that the black spots are smaller in the 2011 image, despite the higher resolution of the 2011 image.
The next question is: is this some kind of shadow? Well, no. It doesn’t look like it.
The team extracted a number of images of light coming from different directions, and the location of the site appears to be consistent. The researchers even found a series of images with dark spots in which the angle of incidence of light (aka the angle at which it hits the surface) gets higher and higher. If the point were a shadow, you would expect it to become more prominent as the angle of incidence increases. That’s not the case – it still becomes less obvious over time. “We don’t think it’s terrain; we don’t think it’s just a shadow,” Phillips told Space.com.
It didn’t end there – the team also looked at images taken in ultraviolet and color (interestingly, the latter showed that the dark spot is reddish-brown, unlike the usual bluish-dark areas on the rest of the moon). None of this provides a simple explanation for the feature.
so, what is it?
“I think it’s more likely [case] “It’s some kind of crater,” Phillips told Space.com. Down, that’s why it has that weird color, or you see that when it hit, it exposed some kind of different color of ice bedrock.
But for nearly every possible, mundane scenario in space research, there’s often a rare, exciting one that contrasts it.
“The really cool explanation would be if it’s actually coming from below somehow; if this reddish color is actually a sign of what’s inside Enceladus,” she said. “It’s unlikely, but it would be really fun.”
Still, while we don’t know what the black spot is, Phillips points out, we can indeed draw something pretty important from its existence: “‘What is it?’ I don’t know the answer, but what I can say is : ‘What can we do with it?’
remember feathers
In short, the researchers believe the dark spot appears to be disappearing because sediment from the icy Enceladus plume may be masking it. “We know that the entire surface is covered in plumes of sediment — like small ice sheets that build up over time,” Phillips said.
Alas, in theory, it makes sense. But when you think about it, there are some outstanding issues here.
For example, the team found that the black spots disappeared in just a few years—meaning that just a few years were enough for the ice plume deposits to form a layer of ice thick enough to cover such a prominent black spot. After all, it is visible from space! However, based on various calculations of dark spots and lunar plume models, Phillips said a similar approach should be taken 100 years Create a layer thick enough to cover such spots.
“However, this may mean that plume deposition models, at least at this location, are underestimated,” she said. “One thing we didn’t take into account, though, was deposition from collisions with E-ring particles.”
E-ring particles refer to ultra-small water ice particles in Saturn’s rings. The team believes that some of these particles may help form the flakes that cover the black spots. But the story of the site’s origins and evolution is, at this point, reflected in the abrupt end to the story of our discovery of it.
There are so many unanswered questions.
“What would be an indication of the deposition rate required to cover a black spot in this time frame? Does the E-ring help cover that black spot? Is there possibly another mechanism?” mused Phillips.
“And, you know, what is that black spot?”