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Screenshot from the Scott Manley's January 30, 2022 video "Deep Space Radiation, Black Holes And Other Questions - Episode 14" https://youtu.be/qtWhv9Ic7Hg Screenshot from the Scott Manley's January 30, 2022 video "Deep Space Radiation, Black Holes And Other Questions - Episode 14" https://youtu.be/qtWhv9Ic7Hg

Scott Manley's January 30, 2022 video Deep Space Radiation, Black Holes And Other Questions - Episode 14 discusses radiation levels and human survivability on Jovian satellites, and after 05:14 says:

...Callisto on the other hand, it seems to be much more manageable if you look at the numbers.

So yeah, if you wanted to mount a mission to Callisto, it wouldn't be too hard, Callisto probably has a fair amount of water ice, and very likely has liquid water in places, just not as much as say Europa.

Now of course if you want to avoid these radiation effects you can go under the surface and that really helps you a whole lot. It's not going to happen in Io because nobody likes swimming in molten lava.

Europa; you could actually in theory go scuba diving underneath the ice, it's really really thick! But the atmosphere - sorry, the gravity of Europa is low enough that it's at the high end of what is possible in scuba with highly technical gear.

Question: Why does Scott Manley say "the gravity of Europa is low enough that it's at the high end of what is possible in scuba with highly technical gear"?

What is it that would be at the "high end" but possible due to gravity of Europa being "low enough"?

Is gravity actually the problem, or is it something else that responds to gravity? Are there some depths where it would be more possible than others?


related to Europa's subsurface water (and potentially contaminating it):


Diagram of Europa's Ice surface and subsurface ocean, from the JPL News feature "Scientists Find Evidence of 'Diving' Tectonic Plates on Europa"

above: Diagram of Europa's Ice surface and subsurface ocean, from the JPL News feature Scientists Find Evidence of 'Diving' Tectonic Plates on Europa.

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    $\begingroup$ I suspect he means that the pressure is humanly tolerable, despite being 20km below the surface. $\endgroup$
    – Antzi
    Feb 1, 2022 at 7:45
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    $\begingroup$ @Antzi Seems problematic. Record depth scuba dive is 332m. Europa's gravity is 13.4% of Earth's. That would make 2.5km depth on Europa have roughly equivalent pressure. Sure it's much deeper but stil a far cry from the 15-25km required. (and no, with 1560km radius, 20km makes no significant difference in gravity.) $\endgroup$
    – SF.
    Feb 1, 2022 at 10:01
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    $\begingroup$ @SF Well, we also need to remove the weight of the atmosphere (since europa does not have one), but that will be a marginal effect ^^ $\endgroup$
    – Antzi
    Feb 1, 2022 at 10:16
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    $\begingroup$ @Antzi 1 bar, or 10 meters Earth depth equivalent / 74m on Europa. $\endgroup$
    – SF.
    Feb 1, 2022 at 10:44

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Using saturation diving it is possible to go much deeper than possible with technical scuba diving. For saturation diving a diving bell is needed to transport the diver from surface to the ground. Compression of the diver before the dive takes some days and decompression after the dive about a week. A hyperbaric chamber is required for compression and decompression and the diving bell should be dockable to the chamber.

The records in deep diving are 332 m scuba diving and 534 m saturation diving from a diving bell. 701 m simulated depth was achieved in an onshore hyperbaric chamber.

On Europa with 13.4 % of Earth's gravity the equivalent depth are 2.48 km, 3.99 km and 5.23 km.

The ice crust of Europa is expected to be 10 to 30 km thick.

So diving Europa seems to be impossible using SCUBA (Self Contained Underwater Breathing Aparatus) as well as saturation diving.

Even an atmospheric diving suit does not suffice for Europa. The record depth is 600m on Earth and 4.48 km on Europa.

In my humble opinion Europa diving is far beyond of what is possible using extremely technical gear. An AUV like the Remus6000 designed for 6 km on Earth may be used for 44 km on Europa.

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