The Supermassive Podcast - BONUS - Where are Earth's rings?

Episode Date: July 19, 2025

What would happen if asteroid Bennu impacted Earth? Can we timelapse Saturn's rings developing? Where are Earth's rings? Plus the solar wind on Mars... The Supermassive team answer YOUR questions. Keep sending questions to [e-mail], on Instagram @SupermassivePod or join The Supermassive Club for ad-free listening and to support the show. Hosted on Acast. See acast.com/privacy for more information.

Hello and welcome to another bonus episode of the Supermassive podcast from the Royal Astronomical Society with me, science journalist Izzy Clark, astrophysicist Dr. Becky Smethurst and the society's Deputy Director, Dr. Robert Massey. Thank you to everyone who's sending in questions or posting them on the forum. And remember, yeah, you can join the supermassive club for £3.99. We've got a star gazing forum in there, book club, or you can just post your questions for the podcast. Right, Robert, shall we start with this one from Kevin Dady? He's emailed us with this question about Bennu. He says, I listened to episode 62 about sample return missions. The description of the surface of Bennu prompted me to think about a possible impact with Earth description of the surface of Bennu prompted me to think

about a possible impact with Earth. Since the surface of Bennu is loose and seems mostly comprised of small pebbles and dust particles, wouldn't this granular and loose surface fly off the asteroid in the upper atmosphere and burn away harmlessly, leaving a hopefully smaller core that could impact Earth. I imagine a spectacular meteor shower preceding the larger core's impact, which because of its reduced size would cause less damage and harmful repercussions, or might this have been considered in the original impact analysis? Yeah, I was thinking about this. It's a good question, Kevin, actually. I was thinking

about this. Would it work like that? Would it look like that? Well, anyway, the context is that Bennu has a 0.037% chance of colliding with Earth in the year 2182. So no need to panic. Right, no need to panic. Very low odds. Right along the way off. It's 500 meters across, so it's a medium-sized asteroid and the majority are much smaller than that. But it is, for that said, a lot smaller than the one that we thought wiped out the dinosaurs 66 million years ago. Now, if it did hit Earth, though, the results wouldn't be great. And you're right that some of the outer material

might burn off, but you have to remember that it's traveling so fast, it's only gonna take a matter of seconds to slam into the atmosphere. It's just so fast that there isn't gonna be much time for the kind of disintegration that you're describing to happen. And there a paper published as it happens in February by Landai and Axel Timerman. They looked to how it would affect our planet. Apart from the impact site itself,

I think most of it would reach the ground, create a crater and so on. The problem is that 400 million tonnes of dust would be lifted into the atmosphere. That could lead to a 4°C drop in temperature and a drop in precipitation, so rain. These effects could last for years. That would obviously hit the biosphere generally, but also lead to a drop in food production, a big drop. Not great all around. I'm sorry not to give you a more optimistic answer there, but yeah, it wouldn't be a meteor shower and a nice gentle dissipation. Unfortunately, it would be rather more derratic than that. Having said that, the optimistic stuff is look, 0.037%, 2182, I think, you know, let's be optimistic. We should be able to deal with this.

Yeah. And Becky, we've had this question from Adam on Instagram. He says, Hi, I always look forward to listening to this podcast every month on the night shift. Appropriate. Very appropriate. Following on from the Uranus episode, it got me thinking about rings and how you said they were caused by a possible collision. Considering our moon was thought to have been a collision with Earth, why are there no rings of debris around Earth? Yeah, good question. Yeah, so it's possible in the giant impact hypothesis of how we thought the moon formed through an impact, you know, with the very early Earth, like, for enough billion years ago, with a Mars-sized kind of object, that there were, after that, you know, in the chaos that just got thrown out after that collision of just everything being liquefied rock, that there may have been some very short-lived rings formed around Earth after that collision. When we're saying short-lived, I mean millennia and not millions of years, right?

Yeah, it's a blip in astronomy time scales, but long in human, right? Now, the reason that we don't have rings anymore is then just sort of like a bit of an interplay with what happened with the material. So if the force of the collision sent material out far enough away from Earth that the self-gravity of that material there meant like the force of gravity between two little lumps of rock was therefore stronger than the force pulled by Earth on those rocks, then they're going to start to clump together, right? Instead of shearing into rings. Yeah. And so that's how we ended up with the moon forming is because that essentially happened. Now any other material

that didn't go that far so that it was sort of more, you know, a stronger effect of gravity was coming from the Earth, like tearing it apart, perhaps with tidal forces, things like this, then anything that would have then formed like a ring like around Saturn or Uranus, that would have actually interacted with the atmosphere of the Earth. Heather Hyslop Okay. Anna Chisholm So, you know, we think about sort of when we see the pictures of the Earth, we think about it as being like, you know, the planet and then you got this like fuzzy atmosphere and there's some line where the atmosphere stops, right?

And you become space is a very big debate at the minute in the sort of like, you know, commercial space industry and like who has been to space and who has not? Have they gone to 80 kilometers? Have they been to 100 kilometers? Et cetera, et cetera. But it said the atmosphere just goes from more dense at the surface to just ever less dense the higher enough up you go. But there are still some molecules there, even, you know, where the Hubble Space Telescope, for example, is orbiting. And that is eventually what would probably kill the Hubble Space Telescope if there was no intervention. It would be the fact that there is

enough atmosphere up there that it would have hit into the Hubble Space Telescope to cause atmospheric drag and slow it down in its orbit and so it would eventually spiral back to Earth. This is how all satellites eventually decay if you leave them there for long enough. And the same thing would be true if you had material in rings around the Earth and, you know, otherwise, they wouldn't have been far enough out to eventually coalesce into the moon. And so any ring that we did have would have just essentially rained back down onto the surface of Earth. OK, thank you, Becky. And Robert, Alex sends this question. In a recent episode, there was a discussion of lobbing ice at Mars to make it habitable.

However, if I recall correctly, Mars lacks a magnetic field which, again if I recall correctly, means anyone from Earth living on the surface would have a short cancer-filled life. Is the solar wind attenuated enough by the time it gets to Mars that it wouldn't be a concern if you could get enough water on the surface Yeah, Alex. So definitely you're quite right. The Mars is not a healthy place to live at the moment the radiation levels are much higher than on the earth because there isn't a Magnetic field to detect the deflector other those are charged particles because you know charged particles electrically charged things get moved around by magnetic field

That's really helpful that That helps protect us on Earth. Also, an astronaut travelling there would get more than a lifetime's limit of radiation just during their voyage. The European Space Agency estimates that to be 700 times higher than on Earth. They said they don't really see it as an acceptable risk unless we can find a way around that. Space agents at the moment would think very hard about doing this before sending people there. So if in theory, and we said why it's quite hard to do, but if in theory we could make Mars have a thick atmosphere, say with a lot of water and carbon dioxide,

then it would definitely help. And it would stop a lot of the particles from reaching the surface. But as we were saying last time, it's just really difficult to bring that much water to Mars. Saturn's rings don't really have enough. Smashing icy bodies into the surface is going to be pretty violent. It's a very destructive thing to do to Mars.

You're going to have to wait a long time for all that to settle down. You certainly don't want any people on the surface while that's happening. And also, I think for my part, there probably isn't life on Mars, I don't know. But if there's something eking out an existence there, I'd quite like to protect it and have a look at it and study it before we decide just to trash it and make a place that we want to live on. You know, I don't think we've got that right. I think we, you know, that would be an extraordinary discovery and we shouldn't put that at risk. Yeah, I think that's a great point. I think I say this all the time, but I do think of

it is just us coming along with grubby hands going, let's touch all of the different things. You're like, no, don't do it. Don't do this colonial thing. We don't need to. It's really interesting. We find love on Mars with some beautiful robot, all those samples coming back to Earth. It will be incredible. Absolutely. I know. I know. I want that to happen so badly. Thanks, Robert. And Becky, we have this final question from Debbie. Hi.

Another question for Dr. Becky, as it has to do with Saturn. I know Saturn's rings weren't always there. Aren't they? I mean, all the ring questions. Yeah, I know. Aren't they relatively recent? Though the timeframe may determine if this is a dumb question or not.

Anyway, using all the images of Saturn, is there a way to get a time lapse of the development of the rings? I mean, wouldn't it be cool to see the development and eventual dissipation of them? Just a thought. Very cool thought. In practice So yes, astronomically speaking, the rings of Saturn are fairly new. They are a hundred to four hundred million years old somewhere in that ballpark. So, you know, if dinosaurs had telescopes, they wouldn't have seen rings on Saturn, for example. In terms of human time scales, however, that is quite long, right? So in terms of like having a time lapse of the development of rings, we have that over like years, decades, you know, if we're lucky, right? So we've not been observing them long enough to see major changes or to have high enough resolution images

to actually put those together. Like, yes, we have sketches of Saturn's rings from hundreds of years ago, but even if we're being generous here, we could maybe say there's 100 years worth of usable images. I think that's probably more like 50 30 something like that. Yeah, Liz can't quite see the twitch in your eye going like, oh, maybe just tumble. So you know, that's if it's 100 years, just to make the maths easy, that's not point not not not 1% of the lifetime of the rings. Not a very sort of like representative time lapse, right? We do actually have a time lapse of

Saturn's rings changing over the space of half an hour using the Hubble Space Telescope. And that actually shows individual, like I say individual particles, we can't see individual particles, but just the particles moving within the rings. You have these things of like what we call spokes of like where there's slightly denser material like clumped together. And you can see those moving around. It's a really cool time lapse if you just Google, you know, Hubble Space Telescope Saturn time lapse, you should be able to find it. And of course, we also have time lapses of the tilts of Saturn's ring changing, right? Because as Saturn orbits the Sun, like the Earth, it has a tilt and so its angle of how we see the rings changes with respect to us, so sometimes they're

you know perfectly edge on, I think they've been about that kind of like now, we don't really see a lot of detail because they're so so thin and slowly they'll tilt back round again so that we can actually see them and we have those kind of time lapses but no time up showing like the development of the rings over millions of years like we would want to but the thought of you know maybe capturing like an eventual dissipation of the rings would be would be very cool I think that would you know just come with constant observation whether the humans will be around long enough for that, I don't rightly know, but we don't just make these archives for nothing. So.

Yeah, fair enough. Fingers crossed, maybe. You never, never know, Debbie. As you say, never say never. Never say never, Debbie, but I wouldn't want to promise that it was in our lifetime. Thanks, Debbie, and thanks everyone else for the questions.

Do keep sending them in, plus your photos or any interesting observations that you've seen. It's podcast at res.ac.uk or find us on Instagram at Supermassive Pod. Oh, I keep forgetting that we have the Supermassive Club as well. So you can post them on there. And thank you to everyone that's posting their pictures in there. There's an amazing one of the International Space Station tracking along the moon. And it's-

Yes, I saw that. Oh, so beautiful. It's such a nice, we get like a nice community growing there as well. It'll be great. Anyway, we'll be back in a couple of weeks with an episode that's going to have been recorded live at the UK Space Conference. Izzy is going to be making a load more astronaut friends. I'm very jealous that I wasn't able to join. So until next time everybody, happy

stargazing.