{"id":57741,"date":"2024-04-16T12:17:32","date_gmt":"2024-04-16T12:17:32","guid":{"rendered":"http:\/\/aff163d7-8f22-4bb5-b3f9-4e1ab101a4bb"},"modified":"2024-04-16T14:09:44","modified_gmt":"2024-04-16T14:09:44","slug":"saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth\/","title":{"rendered":"Saturn’s ‘Death Star’ moon Mimas has a newly-found ocean, unique in the search for life beyond Earth"},"content":{"rendered":"

A newly discovered ocean on Saturn\u2019s moon Mimas could provide a unique place to study the habitability of our Solar System. <\/p>

By Ezzy Pearson\n <\/p>

Published: Tuesday, 16 April 2024 at 12:17 PM<\/p>

\n\n

If you’ve ever heard of Saturn’s moon Mimas, chances are you’re aware of its resemblance to the famous Imperial space station in the Star Wars franchise, but you may not be aware that this moon has an ocean.<\/p>

Mimas’s most prominent feature is without a doubt the huge crater Herschel Crater, which looks remarkably like the circular indentation on the fictional Death Star. <\/p>

Saturn’s moon Mimas has an ocean. Image captured by the Cassini spacecraft. Credit: NASA<\/figcaption><\/figure>
Mimas is a small moon of Saturn; the smallest of the so-called mid-sized icy moons \u2013 394km (246 miles) in diameter.<\/p>
In February 2024, a team of astronomers published a paper announcing the discovery of a large global subsurface ocean on moon Mimas.<\/p>
Val\u00e9ry Lainey is an astronomer based at the Observatoire de Paris who works on the motions of celestial objects in the Solar System, and led the team behind the discovery.<\/p>
We got the chance to speak to Lainey about Mimas the ocean moon and what the discovery could mean for the search for signs of life beyond Earth.<\/p>
$\"Valery$ <\/figure>
What is the relationship between Saturn and Mimas?\u00a0<\/strong><\/h2>
Mimas is big enough to have a roughly spherical shape because of gravity, but it\u2019s probably one of the smallest objects that can.<\/p>
If it were half the size, it would look more like an asteroid<\/a>. The effect of gravity<\/a> also means it has a rocky core and an ice shell.\u00a0<\/p>
Mimas significantly influences the rings of Saturn, contributing greatly in preventing their expansion.<\/p>
If you look at Saturn\u2019s rings<\/a>, there are large gaps between them.<\/p>
The biggest such gap, 4,000\u20135,000km (2,485\u20133,106 miles) wide, is called the Cassini division, and the existence and maintenance of this division is due to Mimas\u2019s gravity.<\/p>
$\"An$
An image of Saturn from Voyager 2. The picture has been colour-enhanced to show in bright details the planet\u2019s surface and the features of the rings. Clearly visible is the gap between the A and B rings, called the Cassini Division. (Credit: NASA\/JPL)<\/figcaption><\/figure>
What did your team discover?<\/strong><\/h2>
We discovered something at Mimas that nobody believed possible: a global ocean under the surface of the moon.<\/p>
The icy shell is typically 20\u201330km (12.4\u201318.6 miles) thick. This was extremely unexpected.<\/p>
Firstly, the surface doesn\u2019t look as though Mimas has any internal activity; there\u2019s no resurfacing.<\/p>
If you have a global ocean for a long time \u2013 as on Mimas, where more than 50% of the volume is liquid water \u2013 you expect some material to eventually come up to the surface.<\/p>
You\u2019d expect surface faults and possible geyser activity which should fill any craters to create a smooth plain, like on Enceladus.<\/p>
Which is not the case at all with Mimas. This suggests the moon’s ocean is very young.<\/p>
$\"Global$
Global map of Saturn’s moon Mimas, discovered to have a global ocean. Map created using data captured by the Voyager and Cassini missions. Credit: NASA\/JPL\/Space Science Institute<\/figcaption><\/figure>
How did you discover the ocean?<\/strong><\/h2>
We found that, when monitoring the rotation of Mimas, there were small wobbles or oscillations.<\/p>
These were expected, but one of them was much larger than we predicted. We decided to investigate what was causing this large oscillation.<\/p>
Two scenarios were possible: one was that the rocky core of Mimas was elongated like a cigar, the other possibility was a global ocean on the moon.<\/p>
To discriminate between the two scenarios, we looked at the drift in Mimas\u2019s orbit, which was around 10km (6.2 miles) over the 13 years of the Cassini mission.<\/p>
Because of the beautiful images of the Cassini mission, we succeeded in getting such precision and accuracy that we were able to say \u201cNo, this is not an elongated core\u201d.\u00a0<\/p>
$\"Saturn's$
Saturn’s moon Mimas is dwarfed by Saturn’s rings in this image captured by the Cassini spacecraft on 18 July 2005. Credit: NASA\/JPL\/Space Science Institute<\/figcaption><\/figure>
How does moon Mimas have a \u2018young\u2019 ocean?<\/strong><\/h2>
We believe Mimas\u2019s ocean may have formed in the last 25 million years.<\/p>
Initially we believed the Saturn system formed at the same time as Saturn, around 4.5 billion years ago.<\/p>
When suggesting the formation of an ocean moon so late in the Solar System, you need to have a strong argument to explain why it\u2019s happening now.<\/p>
The answer comes down to strong tides on Saturn, and the youthfulness of Saturn\u2019s rings, which were recently suggested to be 100 to 200 million years old.\u00a0<\/p>
$\"A$
A view of Saturn\u2019s rings captured by the Cassini spacecraft on 21 July 2016. Just below rings can be spotted Saturn\u2019s tiny moon Mimas.Credit: NASA\/JPL-Caltech\/Space Science Institute<\/figcaption><\/figure>
Is Mimas a good place to look for signs of life?<\/strong>\u00a0<\/h2>
It is a good place for interesting chemistry.<\/p>
At Mimas\u2019s seafloor, where you have liquid water in contact with silicates in the moon\u2019s rocky core, the temperature will also be relatively warm.<\/p>
This is possibly the youngest place in the Solar System that could be habitable.<\/p>
It is also possible that Mimas could be the product of former, bigger moons.<\/p>
You may then have compounds in Mimas\u2019s ocean that are more evolved because of what happened in these former generations.<\/p>
That is a completely open question, meaning that Mimas is a very different type of object.\u00a0<\/p>
$\"The$
The other side of Mimas! A view towards the southern hemisphere on the anti-Saturn side of Mimas. Credit: NASA\/JPL\/Space Science Institute<\/figcaption><\/figure>
What\u2019s next for your team?\u00a0<\/strong><\/h2>
It would be interesting to know the fate of the ocean. Will it freeze eventually? Or get excited again?<\/p>
We would also like to better know the thickness of the icy shell and the temperature at the sea floor.<\/p>
For this, we need to know more about the processes in Mimas\u2019s core.<\/p>
We also want to learn more about Mimas\u2019s interaction with Saturn\u2019s other moons, which will have caused it to heat in the last 25 million years.<\/p>
We know that these interactions are what caused the heating, but we don\u2019t yet know which moons were in play.<\/p>
***This interview appeared in the May 2024 issue of BBC Sky at Night Magazine<\/em><\/strong><\/p> <\/body><\/html>\n***
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A newly discovered ocean on Saturn\u2019s moon Mimas could provide a unique place to study the habitability of our Solar System. <\/p>\n","protected":false},"author":24,"featured_media":57742,"template":"","categories":[1],"acf":{"readingTimeMinutes":"5"},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2024\/04\/saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth.jpg",1200,800,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2024\/04\/saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2024\/04\/saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth-300x200.jpg",300,200,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2024\/04\/saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth-768x512.jpg",768,512,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2024\/04\/saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth-1024x683.jpg",800,534,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2024\/04\/saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth.jpg",1200,800,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2024\/04\/saturns-death-star-moon-mimas-has-a-newly-found-ocean-unique-in-the-search-for-life-beyond-earth.jpg",1200,800,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"A newly discovered ocean on Saturn\u2019s moon Mimas could provide a unique place to study the habitability of our Solar System.","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed\/57741"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/rss_feed"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/rss_feed"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/57742"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=57741"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=57741"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}

Saturn’s moon Mimas has an ocean. Image captured by the Cassini spacecraft. Credit: NASA<\/figcaption><\/figure>
Mimas is a small moon of Saturn; the smallest of the so-called mid-sized icy moons \u2013 394km (246 miles) in diameter.<\/p>
In February 2024, a team of astronomers published a paper announcing the discovery of a large global subsurface ocean on moon Mimas.<\/p>
Val\u00e9ry Lainey is an astronomer based at the Observatoire de Paris who works on the motions of celestial objects in the Solar System, and led the team behind the discovery.<\/p>
We got the chance to speak to Lainey about Mimas the ocean moon and what the discovery could mean for the search for signs of life beyond Earth.<\/p>
$\"Valery$ <\/figure>
What is the relationship between Saturn and Mimas?\u00a0<\/strong><\/h2>
Mimas is big enough to have a roughly spherical shape because of gravity, but it\u2019s probably one of the smallest objects that can.<\/p>
If it were half the size, it would look more like an asteroid<\/a>. The effect of gravity<\/a> also means it has a rocky core and an ice shell.\u00a0<\/p>
Mimas significantly influences the rings of Saturn, contributing greatly in preventing their expansion.<\/p>
If you look at Saturn\u2019s rings<\/a>, there are large gaps between them.<\/p>
The biggest such gap, 4,000\u20135,000km (2,485\u20133,106 miles) wide, is called the Cassini division, and the existence and maintenance of this division is due to Mimas\u2019s gravity.<\/p>
$\"An$
An image of Saturn from Voyager 2. The picture has been colour-enhanced to show in bright details the planet\u2019s surface and the features of the rings. Clearly visible is the gap between the A and B rings, called the Cassini Division. (Credit: NASA\/JPL)<\/figcaption><\/figure>
What did your team discover?<\/strong><\/h2>
We discovered something at Mimas that nobody believed possible: a global ocean under the surface of the moon.<\/p>
The icy shell is typically 20\u201330km (12.4\u201318.6 miles) thick. This was extremely unexpected.<\/p>
Firstly, the surface doesn\u2019t look as though Mimas has any internal activity; there\u2019s no resurfacing.<\/p>
If you have a global ocean for a long time \u2013 as on Mimas, where more than 50% of the volume is liquid water \u2013 you expect some material to eventually come up to the surface.<\/p>
You\u2019d expect surface faults and possible geyser activity which should fill any craters to create a smooth plain, like on Enceladus.<\/p>
Which is not the case at all with Mimas. This suggests the moon’s ocean is very young.<\/p>
$\"Global$
Global map of Saturn’s moon Mimas, discovered to have a global ocean. Map created using data captured by the Voyager and Cassini missions. Credit: NASA\/JPL\/Space Science Institute<\/figcaption><\/figure>
How did you discover the ocean?<\/strong><\/h2>
We found that, when monitoring the rotation of Mimas, there were small wobbles or oscillations.<\/p>
These were expected, but one of them was much larger than we predicted. We decided to investigate what was causing this large oscillation.<\/p>
Two scenarios were possible: one was that the rocky core of Mimas was elongated like a cigar, the other possibility was a global ocean on the moon.<\/p>
To discriminate between the two scenarios, we looked at the drift in Mimas\u2019s orbit, which was around 10km (6.2 miles) over the 13 years of the Cassini mission.<\/p>
Because of the beautiful images of the Cassini mission, we succeeded in getting such precision and accuracy that we were able to say \u201cNo, this is not an elongated core\u201d.\u00a0<\/p>
$\"Saturn's$
Saturn’s moon Mimas is dwarfed by Saturn’s rings in this image captured by the Cassini spacecraft on 18 July 2005. Credit: NASA\/JPL\/Space Science Institute<\/figcaption><\/figure>
How does moon Mimas have a \u2018young\u2019 ocean?<\/strong><\/h2>
We believe Mimas\u2019s ocean may have formed in the last 25 million years.<\/p>
Initially we believed the Saturn system formed at the same time as Saturn, around 4.5 billion years ago.<\/p>
When suggesting the formation of an ocean moon so late in the Solar System, you need to have a strong argument to explain why it\u2019s happening now.<\/p>
The answer comes down to strong tides on Saturn, and the youthfulness of Saturn\u2019s rings, which were recently suggested to be 100 to 200 million years old.\u00a0<\/p>
$\"A$
A view of Saturn\u2019s rings captured by the Cassini spacecraft on 21 July 2016. Just below rings can be spotted Saturn\u2019s tiny moon Mimas.Credit: NASA\/JPL-Caltech\/Space Science Institute<\/figcaption><\/figure>
Is Mimas a good place to look for signs of life?<\/strong>\u00a0<\/h2>
It is a good place for interesting chemistry.<\/p>
At Mimas\u2019s seafloor, where you have liquid water in contact with silicates in the moon\u2019s rocky core, the temperature will also be relatively warm.<\/p>
This is possibly the youngest place in the Solar System that could be habitable.<\/p>
It is also possible that Mimas could be the product of former, bigger moons.<\/p>
You may then have compounds in Mimas\u2019s ocean that are more evolved because of what happened in these former generations.<\/p>
That is a completely open question, meaning that Mimas is a very different type of object.\u00a0<\/p>
$\"The$
The other side of Mimas! A view towards the southern hemisphere on the anti-Saturn side of Mimas. Credit: NASA\/JPL\/Space Science Institute<\/figcaption><\/figure>
What\u2019s next for your team?\u00a0<\/strong><\/h2>
It would be interesting to know the fate of the ocean. Will it freeze eventually? Or get excited again?<\/p>
We would also like to better know the thickness of the icy shell and the temperature at the sea floor.<\/p>
For this, we need to know more about the processes in Mimas\u2019s core.<\/p>
We also want to learn more about Mimas\u2019s interaction with Saturn\u2019s other moons, which will have caused it to heat in the last 25 million years.<\/p>
We know that these interactions are what caused the heating, but we don\u2019t yet know which moons were in play.<\/p>
***This interview appeared in the May 2024 issue of BBC Sky at Night Magazine<\/em><\/strong><\/p> <\/body><\/html>\n***
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