scishow space
Is Our Solar System Missing Moons?
YouTube: | https://youtube.com/watch?v=nO233LsL7lc |
Previous: | The Future of the Search for Life |
Next: | JWST: Looking Beyond The Pretty Pictures |
Categories
Statistics
View count: | 77,506 |
Likes: | 4,098 |
Comments: | 127 |
Duration: | 06:41 |
Uploaded: | 2023-01-17 |
Last sync: | 2024-10-02 03:15 |
Citation
Citation formatting is not guaranteed to be accurate. | |
MLA Full: | "Is Our Solar System Missing Moons?" YouTube, uploaded by , 17 January 2023, www.youtube.com/watch?v=nO233LsL7lc. |
MLA Inline: | (, 2023) |
APA Full: | . (2023, January 17). Is Our Solar System Missing Moons? [Video]. YouTube. https://youtube.com/watch?v=nO233LsL7lc |
APA Inline: | (, 2023) |
Chicago Full: |
, "Is Our Solar System Missing Moons?", January 17, 2023, YouTube, 06:41, https://youtube.com/watch?v=nO233LsL7lc. |
You might be pretty confident that when a moon is there it’s there to stay, but that’s not always the case. Moons may have a history of disappearing.
Hosted by: Savannah Geary (they/them)
Correction:
05:19 Well, this is half right. The moons don't actually orbit the same distance from Mars and orbit on opposite sides of the synchronous radius. Sorry about the mistake!
----------
Huge thanks go to the following Patreon supporter for helping us keep SciShow Space free for everyone forever: Jason A Saslow, David Brooks, and AndyGneiss!
Support SciShow Space by becoming a patron on Patreon: https://www.patreon.com/SciShowSpace
Or by checking out our awesome space pins and other products over at DFTBA Records: http://dftba.com/scishow
----------
Looking for SciShow elsewhere on the internet?
SciShow on TikTok: https://www.tiktok.com/@scishow
SciShow Tangents Podcast: http://www.scishowtangents.org
Facebook: http://www.facebook.com/scishow
Twitter: http://www.twitter.com/scishow
Instagram: http://instagram.com/thescishow
----------
Sources:
https://solarsystem.nasa.gov/moons/saturn-moons/overview
https://solarsystem.nasa.gov/planets/saturn/in-depth/#otp_rings
https://solarsystem.nasa.gov/missions/cassini/overview/
https://news.berkeley.edu/2019/01/17/saturn-hasnt-always-had-rings/
https://www.science.org/doi/10.1126/science.aat2965
https://www.science.org/doi/10.1126/science.abn1234
https://www.nature.com/articles/s41550-020-01284-x
https://solarsystem.nasa.gov/moons/jupiter-moons/overview
https://www.universetoday.com/44796/galilean-moons/
https://arxiv.org/pdf/0812.4995.pdf
https://arxiv.org/abs/1801.06094
https://arxiv.org/pdf/1909.00285.pdf
https://www.nature.com/articles/s41550-021-01306-2
https://iopscience.iop.org/article/10.3847/PSJ/ac88d2
Image Sources:
https://www.gettyimages.com/detail/video/adult-woman-dropping-all-stuff-out-from-bag-searching-stock-footage/1358112445
https://www.gettyimages.com/detail/video/twinkling-stars-motion-graphics-with-night-background-stock-footage/1355123496
https://www.gettyimages.com/detail/illustration/realistic-full-moon-royalty-free-illustration/1318457488
https://www.gettyimages.com/detail/video/saturn-is-a-huge-planet-of-the-solar-system-with-stock-footage/1323556900
https://www.gettyimages.com/detail/video/cassini-spacecraft-next-to-saturn-stock-footage/507622466
https://commons.wikimedia.org/wiki/File:Saturn_from_Cassini_Orbiter_(2004-10-06).jpg
https://solarsystem.nasa.gov/resources/657/a-farewell-to-saturn/?category=planets_saturn
https://solarsystem.nasa.gov/resources/209/surge-in-the-ring/?category=planets_saturn
https://solarsystem.nasa.gov/resources/17849/translucent-arcs/?category=planets_saturn
https://solarsystem.nasa.gov/resources/2490/saturns-rings-shine-in-hubble-portrait/?category=planets_saturn
https://solarsystem.nasa.gov/resources/2486/hubbles-new-portrait-of-jupiter/?category=planets_jupiter
https://www.youtube.com/watch?v=xh3EKDghbuU
https://photojournal.jpl.nasa.gov/catalog/PIA00600
https://www.gettyimages.com/detail/video/ice-moon-europa-on-the-background-of-the-large-gas-stock-footage/1184147596
https://www.gettyimages.com/detail/video/approaching-jupiter-stock-footage/902728712
https://en.wikipedia.org/wiki/File:Francisco_de_Goya,_Saturno_devorando_a_su_hijo_(1819-1823).jpg
https://commons.wikimedia.org/wiki/File:Terrestrial_planet_sizes2.jpg
https://commons.wikimedia.org/wiki/File:Phobos_deimos_diff.jpg
https://www.gettyimages.com/detail/video/space-background-valles-marineris-in-mars-stock-footage/1373047089
https://www.gettyimages.com/detail/photo/planet-mars-with-it-moons-phobos-and-deimos-royalty-free-image/912255196
https://solarsystem.nasa.gov/resources/2273/hubble-sees-phobos-orbiting-mars/?category=planets_mars
https://www.gettyimages.com/detail/video/close-up-fly-by-of-the-planet-saturn-stock-footage/91809141
https://www.gettyimages.com/detail/video/jupiter-in-open-space-stock-footage/1203912979
https://www.gettyimages.com/detail/video/orbiting-planet-mars-high-quality-4k-cg-animation-stock-footage/1169225320
https://www.gettyimages.com/detail/video/full-moon-and-leaves-stock-footage/1414640278
Hosted by: Savannah Geary (they/them)
Correction:
05:19 Well, this is half right. The moons don't actually orbit the same distance from Mars and orbit on opposite sides of the synchronous radius. Sorry about the mistake!
----------
Huge thanks go to the following Patreon supporter for helping us keep SciShow Space free for everyone forever: Jason A Saslow, David Brooks, and AndyGneiss!
Support SciShow Space by becoming a patron on Patreon: https://www.patreon.com/SciShowSpace
Or by checking out our awesome space pins and other products over at DFTBA Records: http://dftba.com/scishow
----------
Looking for SciShow elsewhere on the internet?
SciShow on TikTok: https://www.tiktok.com/@scishow
SciShow Tangents Podcast: http://www.scishowtangents.org
Facebook: http://www.facebook.com/scishow
Twitter: http://www.twitter.com/scishow
Instagram: http://instagram.com/thescishow
----------
Sources:
https://solarsystem.nasa.gov/moons/saturn-moons/overview
https://solarsystem.nasa.gov/planets/saturn/in-depth/#otp_rings
https://solarsystem.nasa.gov/missions/cassini/overview/
https://news.berkeley.edu/2019/01/17/saturn-hasnt-always-had-rings/
https://www.science.org/doi/10.1126/science.aat2965
https://www.science.org/doi/10.1126/science.abn1234
https://www.nature.com/articles/s41550-020-01284-x
https://solarsystem.nasa.gov/moons/jupiter-moons/overview
https://www.universetoday.com/44796/galilean-moons/
https://arxiv.org/pdf/0812.4995.pdf
https://arxiv.org/abs/1801.06094
https://arxiv.org/pdf/1909.00285.pdf
https://www.nature.com/articles/s41550-021-01306-2
https://iopscience.iop.org/article/10.3847/PSJ/ac88d2
Image Sources:
https://www.gettyimages.com/detail/video/adult-woman-dropping-all-stuff-out-from-bag-searching-stock-footage/1358112445
https://www.gettyimages.com/detail/video/twinkling-stars-motion-graphics-with-night-background-stock-footage/1355123496
https://www.gettyimages.com/detail/illustration/realistic-full-moon-royalty-free-illustration/1318457488
https://www.gettyimages.com/detail/video/saturn-is-a-huge-planet-of-the-solar-system-with-stock-footage/1323556900
https://www.gettyimages.com/detail/video/cassini-spacecraft-next-to-saturn-stock-footage/507622466
https://commons.wikimedia.org/wiki/File:Saturn_from_Cassini_Orbiter_(2004-10-06).jpg
https://solarsystem.nasa.gov/resources/657/a-farewell-to-saturn/?category=planets_saturn
https://solarsystem.nasa.gov/resources/209/surge-in-the-ring/?category=planets_saturn
https://solarsystem.nasa.gov/resources/17849/translucent-arcs/?category=planets_saturn
https://solarsystem.nasa.gov/resources/2490/saturns-rings-shine-in-hubble-portrait/?category=planets_saturn
https://solarsystem.nasa.gov/resources/2486/hubbles-new-portrait-of-jupiter/?category=planets_jupiter
https://www.youtube.com/watch?v=xh3EKDghbuU
https://photojournal.jpl.nasa.gov/catalog/PIA00600
https://www.gettyimages.com/detail/video/ice-moon-europa-on-the-background-of-the-large-gas-stock-footage/1184147596
https://www.gettyimages.com/detail/video/approaching-jupiter-stock-footage/902728712
https://en.wikipedia.org/wiki/File:Francisco_de_Goya,_Saturno_devorando_a_su_hijo_(1819-1823).jpg
https://commons.wikimedia.org/wiki/File:Terrestrial_planet_sizes2.jpg
https://commons.wikimedia.org/wiki/File:Phobos_deimos_diff.jpg
https://www.gettyimages.com/detail/video/space-background-valles-marineris-in-mars-stock-footage/1373047089
https://www.gettyimages.com/detail/photo/planet-mars-with-it-moons-phobos-and-deimos-royalty-free-image/912255196
https://solarsystem.nasa.gov/resources/2273/hubble-sees-phobos-orbiting-mars/?category=planets_mars
https://www.gettyimages.com/detail/video/close-up-fly-by-of-the-planet-saturn-stock-footage/91809141
https://www.gettyimages.com/detail/video/jupiter-in-open-space-stock-footage/1203912979
https://www.gettyimages.com/detail/video/orbiting-planet-mars-high-quality-4k-cg-animation-stock-footage/1169225320
https://www.gettyimages.com/detail/video/full-moon-and-leaves-stock-footage/1414640278
It’s just one of those days, you know?
You’re on your way out the door, you pat your pocket, and you don’t hear the familiar jingle of your keys. So it’s time to turn the house upside down! If a planet had feelings, maybe it would experience the same sense of confusion and frustration when a moon that it swears was there the last time it looked has now vanished.
A disappearing moon may sound like Science Fiction, but there are a lot of clues out there that suggest this has happened in our own solar system more than once. Let’s start out with the planet that has the most moons to keep track of, 83 so far, and the most obvious evidence that a moon has gone missing: Saturn. It’s famous for its gorgeous rings, vast collections of pebbles, ice, and dust that circle the planet. By reflecting the Sun’s rays, they shine almost as brightly as the planet itself. But that light, which gives clues about the composition of the rings, hides a secret: The rings are a lot younger than the planet.
Back in 2017, the Cassini spacecraft was approaching the end of its 20-year mission studying Saturn and its many moons. So astronomers felt it was time to take a risky series of dives between the rings. And those dives revealed the total mass of all that ring matter was smaller than it ought to be, at least assuming they had been around for Saturn’s entire four and a half billion year lifespan.
Because they’re largely made of ice, the rings would start off bright and shiny, and would dull with time as they accumulated more and more dust. The heavier the rings, the older they are. But Cassini’s data suggest they’re only tens of millions of years old.
Why were they so late to the planet-making party? Well, according to a paper published in 2022, some astronomers think that Saturn ripped apart one of its own moons that strayed a little too close. You see, as a small body like a moon gets closer to a really large one like a planet, the tidal forces get stronger and stronger.
Tidal forces are a result of the fact that the strength of gravity decreases quickly with distance. So as a planet tugs on a moon, the gravity is stronger on the side of the moon that’s facing the planet, and weaker on the side that isn’t. The closer that moon is to the planet, the stronger the gravitational force, and the more important the difference between close- and far-side becomes.
If a moon gets too close, those tidal forces are so large that they overpower the moon’s own gravity holding all of its bits and pieces together. So there’s a big no-go zone around the planet. A point of no return called the Roche Limit.
Any moon that slips inside will be torn asunder and smeared out into a ring. Bad news for the moon, good news for anyone who likes looking at pretty planetary structures. This transformation from moon to ring led the team to propose the name “Chrysalis” for this hypothetical destroyed moon. So Saturn didn’t exactly lose Chrysalis.
It’s more like it forgot it was in its back pocket and sat down, smushing it. But Saturn’s rings aren’t the only clue that a moon went missing. If Chrysalis really did exist, its disappearance would also help explain why Saturn has the specific tilt it does.
To be clear, there are other hypotheses that explain Saturn’s awkward tilt, but none can also explain why Saturn’s rings are so much younger than the rest of it. Moving one planet closer to the Sun, Jupiter also seems to have lost some moons. Today it has at least 80, but it probably managed to misplace a bunch more, billions of years ago.
Unlike Saturn, which may have proverbially sat on one of its moons, Jupiter may have eaten them. See, based on simulations of the early Solar System, astronomers have estimates for how much matter should have been collapsing to form Jupiter, with leftover chunks becoming moons. Four of those leftover chunks are Jupiter’s main moons.
Ganymede, Callisto, Io, and Europa. They’re collectively named the Galilean moons, after the guy who discovered them, and make up over 99% of all the mass orbiting Jupiter. But according to these simulations, there was enough stuff to make at least four more sets of Galilean moons, which aren’t there. The simulations may be inaccurate.
They are trying to explain events that happened four and a half billion years ago, after all. But some researchers have proposed that these moons did exist way back when. Unfortunately for those moons, because there was so much building material around them, they got too massive for their own good.
After reaching some critical mass, these early moons just weren’t moving fast enough to escape their planet’s grasp. They started spiraling downward, and eventually got gobbled up. Which, for you mythology nerds, is really more of a Saturn thing.
During the millions of years it took Jupiter to form, this could have happened several times over. According to this hypothesis, the Galilean moons were part of the last generation of moons, and survived because there wasn’t enough material for them to reach that critical size. Compared to these gas giants, the terrestrial worlds have way fewer moons. But that doesn’t mean they’re any more careful with them!
Mars has two tiny natural satellites, named after the Greek gods of fear and despair: Phobos and Deimos. And there’s a bit of an argument going on in the astronomical community about where these moons came from. Did they form alongside Mars? Did a lonely Mars capture two wayward asteroids that strayed too far from the asteroid belt?
Well, in 2021 one team of astronomers suggested that Mars captured just one asteroid about 30 kilometers across, the size of Phobos and Deimos combined. Somewhere between 1 and 2.7 billion years ago, they suggest it got smashed apart. Phobos and Deimos are just what’s left.
The team noticed that the moons orbit on opposite sides but the same distance from Mars. That’s a weird coincidence if they were just two independently captured asteroids. However, they got called out by another team in 2022, or at least the math they used did. The second team took issue with the fact that the first group didn’t fully simulate what would happen after the breakup.
According to their newer study, if Phobos and Deimos formed from some large asteroid breaking apart, they would have hit each other pretty quickly and broken up into even more pieces! That’s not what we see when we look up in the night sky, so they say the first group is wrong. So Saturn may have smushed a moon, Jupiter might have eaten lots of moons, and Mars, well, until we get a better idea of where Phobos and Deimos came from, Mars is missing moons in more ways than one!
Understanding how a planet can manage to lose a moon is fascinating in its own right, but it also gives us tools to better understand Earth’s relationship with our own natural satellite, whether it eventually leaves us or not. If you’re wondering if the Earth has ever lost a moon, the answer is yes! Maybe. It depends on your definition of “moon.” We’ve already released a video on that, and you can check it out here!
And as for your keys, the science is still out on that. Maybe try inside the fridge. And thanks for watching SciShow Space.
You’re on your way out the door, you pat your pocket, and you don’t hear the familiar jingle of your keys. So it’s time to turn the house upside down! If a planet had feelings, maybe it would experience the same sense of confusion and frustration when a moon that it swears was there the last time it looked has now vanished.
A disappearing moon may sound like Science Fiction, but there are a lot of clues out there that suggest this has happened in our own solar system more than once. Let’s start out with the planet that has the most moons to keep track of, 83 so far, and the most obvious evidence that a moon has gone missing: Saturn. It’s famous for its gorgeous rings, vast collections of pebbles, ice, and dust that circle the planet. By reflecting the Sun’s rays, they shine almost as brightly as the planet itself. But that light, which gives clues about the composition of the rings, hides a secret: The rings are a lot younger than the planet.
Back in 2017, the Cassini spacecraft was approaching the end of its 20-year mission studying Saturn and its many moons. So astronomers felt it was time to take a risky series of dives between the rings. And those dives revealed the total mass of all that ring matter was smaller than it ought to be, at least assuming they had been around for Saturn’s entire four and a half billion year lifespan.
Because they’re largely made of ice, the rings would start off bright and shiny, and would dull with time as they accumulated more and more dust. The heavier the rings, the older they are. But Cassini’s data suggest they’re only tens of millions of years old.
Why were they so late to the planet-making party? Well, according to a paper published in 2022, some astronomers think that Saturn ripped apart one of its own moons that strayed a little too close. You see, as a small body like a moon gets closer to a really large one like a planet, the tidal forces get stronger and stronger.
Tidal forces are a result of the fact that the strength of gravity decreases quickly with distance. So as a planet tugs on a moon, the gravity is stronger on the side of the moon that’s facing the planet, and weaker on the side that isn’t. The closer that moon is to the planet, the stronger the gravitational force, and the more important the difference between close- and far-side becomes.
If a moon gets too close, those tidal forces are so large that they overpower the moon’s own gravity holding all of its bits and pieces together. So there’s a big no-go zone around the planet. A point of no return called the Roche Limit.
Any moon that slips inside will be torn asunder and smeared out into a ring. Bad news for the moon, good news for anyone who likes looking at pretty planetary structures. This transformation from moon to ring led the team to propose the name “Chrysalis” for this hypothetical destroyed moon. So Saturn didn’t exactly lose Chrysalis.
It’s more like it forgot it was in its back pocket and sat down, smushing it. But Saturn’s rings aren’t the only clue that a moon went missing. If Chrysalis really did exist, its disappearance would also help explain why Saturn has the specific tilt it does.
To be clear, there are other hypotheses that explain Saturn’s awkward tilt, but none can also explain why Saturn’s rings are so much younger than the rest of it. Moving one planet closer to the Sun, Jupiter also seems to have lost some moons. Today it has at least 80, but it probably managed to misplace a bunch more, billions of years ago.
Unlike Saturn, which may have proverbially sat on one of its moons, Jupiter may have eaten them. See, based on simulations of the early Solar System, astronomers have estimates for how much matter should have been collapsing to form Jupiter, with leftover chunks becoming moons. Four of those leftover chunks are Jupiter’s main moons.
Ganymede, Callisto, Io, and Europa. They’re collectively named the Galilean moons, after the guy who discovered them, and make up over 99% of all the mass orbiting Jupiter. But according to these simulations, there was enough stuff to make at least four more sets of Galilean moons, which aren’t there. The simulations may be inaccurate.
They are trying to explain events that happened four and a half billion years ago, after all. But some researchers have proposed that these moons did exist way back when. Unfortunately for those moons, because there was so much building material around them, they got too massive for their own good.
After reaching some critical mass, these early moons just weren’t moving fast enough to escape their planet’s grasp. They started spiraling downward, and eventually got gobbled up. Which, for you mythology nerds, is really more of a Saturn thing.
During the millions of years it took Jupiter to form, this could have happened several times over. According to this hypothesis, the Galilean moons were part of the last generation of moons, and survived because there wasn’t enough material for them to reach that critical size. Compared to these gas giants, the terrestrial worlds have way fewer moons. But that doesn’t mean they’re any more careful with them!
Mars has two tiny natural satellites, named after the Greek gods of fear and despair: Phobos and Deimos. And there’s a bit of an argument going on in the astronomical community about where these moons came from. Did they form alongside Mars? Did a lonely Mars capture two wayward asteroids that strayed too far from the asteroid belt?
Well, in 2021 one team of astronomers suggested that Mars captured just one asteroid about 30 kilometers across, the size of Phobos and Deimos combined. Somewhere between 1 and 2.7 billion years ago, they suggest it got smashed apart. Phobos and Deimos are just what’s left.
The team noticed that the moons orbit on opposite sides but the same distance from Mars. That’s a weird coincidence if they were just two independently captured asteroids. However, they got called out by another team in 2022, or at least the math they used did. The second team took issue with the fact that the first group didn’t fully simulate what would happen after the breakup.
According to their newer study, if Phobos and Deimos formed from some large asteroid breaking apart, they would have hit each other pretty quickly and broken up into even more pieces! That’s not what we see when we look up in the night sky, so they say the first group is wrong. So Saturn may have smushed a moon, Jupiter might have eaten lots of moons, and Mars, well, until we get a better idea of where Phobos and Deimos came from, Mars is missing moons in more ways than one!
Understanding how a planet can manage to lose a moon is fascinating in its own right, but it also gives us tools to better understand Earth’s relationship with our own natural satellite, whether it eventually leaves us or not. If you’re wondering if the Earth has ever lost a moon, the answer is yes! Maybe. It depends on your definition of “moon.” We’ve already released a video on that, and you can check it out here!
And as for your keys, the science is still out on that. Maybe try inside the fridge. And thanks for watching SciShow Space.