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Thread: NASA's Next Big Mission: Dragonfly to Saturn's moon Titan

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    Veteran Member James Brown's Avatar
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    Low-frequency radio waves can penetrate ice. Although I don't know if that's sufficient for the transmitting of data.

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    Fair dinkum thinkum bilby's Avatar
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    Quote Originally Posted by James Brown View Post
    Low-frequency radio waves can penetrate ice. Although I don't know if that's sufficient for the transmitting of data.
    Depends how slow you are prepared to go; and perhaps more importantly in this context, how large an aerial array you can have.

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    Contributor DBT's Avatar
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    An orbiter could sample Europa's ocean from its plumes. If there is life to be found in its oceans, perhaps signs of its presence could be found in these samples. An orbiter could alsp measure ice thickness in fissures, chaotic regions, etc, which would get the ball rolling for more ambitious programs such as firing probes into fissures......

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    Contributor skepticalbip's Avatar
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    Quote Originally Posted by James Brown View Post
    Low-frequency radio waves can penetrate ice. Although I don't know if that's sufficient for the transmitting of data.
    Actually ice is fairly transparent to even high frequency radio waves although water is not. Easily confirmed at home by placing a really cold and dry ice cube in the microwave oven (~2.4 MHz). It will not melt. Wet the surface of that ice cube (a thin layer of water) and the water on the surface of the ice will absorb the microwaves, heat up, and melt the ice cube.

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    Quote Originally Posted by bilby View Post
    I rather like this idea. A modified RTG could do a great job - and they are already designed to withstand crashing back to Earth in the event of a launch problem, so a fairly hard landing could be acceptable.

    I suspect the big problem would be communication back to the orbiter - several km of ice is a pretty effective shield. And pulling a cable down from a 'base station' which remains on the surface would have issues as the water in the hole refreezes. Perhaps some kind of 'snow blower' - a pump that sprays the meltwater out of and away from the hole as it is drilled - could solve that problem; Though your probe would likely be instantly frozen in place once it breaks through the ice.
    Seems to me existing technology could handle this problem.

    https://en.wikipedia.org/wiki/Wire-guided_missile

    The unspooling happens in the melted water around the radioactive sphere; the trailing wire is frozen in place but it no longer needs to move.

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    Quote Originally Posted by DBT View Post
    Looks like an interesting mission. I wonder why they chose that rather than a lander on Europa (or a close flyby) to sample the material ejected from the subsurface ocean, with perhaps a chance at finding signs of life?

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    Quote Originally Posted by James Brown View Post
    What about a radioactive sphere landed on Europa? It melts the ice and sinks down to the waters below. Then it opens its sensors and sees what it can see, transmitting the results to the orbiter overhead.
    I think it would be doable.
    But Europa is very cold, you'd need a lot of RTG power to melt through. Also, it has a weak surface gravity, a little weaker than the Moon. Thus it might take a while for the sphere to sink all the way through the ice, if it is really 10km thick or more.

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    Quote Originally Posted by James Brown View Post
    Low-frequency radio waves can penetrate ice. Although I don't know if that's sufficient for the transmitting of data.
    Low-frequency here means 120-240 MHz according to the article. That is not too bad for communications, esp. since the probe can use all the bandwidth and is not limited to a narrow channel like we are on Earth.

    It's nothing like very low frequency (VLF) and extremely low frequency (ELF) bands used for communicating with submerged submarines where such low frequencies are necessary because conductive saltwater absorbs higher frequency radio waves too much. At these frequencies communication speeds are indeed very slow.

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    Quote Originally Posted by skepticalbip View Post
    Quote Originally Posted by James Brown View Post
    Low-frequency radio waves can penetrate ice. Although I don't know if that's sufficient for the transmitting of data.
    Actually ice is fairly transparent to even high frequency radio waves although water is not. Easily confirmed at home by placing a really cold and dry ice cube in the microwave oven (~2.4 MHz). It will not melt. Wet the surface of that ice cube (a thin layer of water) and the water on the surface of the ice will absorb the microwaves, heat up, and melt the ice cube.
    According to the article, ice tends to reflect higher frequency waves, not transmit them.
    Also, microwave ovens work at ~2.4 GHz - not MHz.

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    Contributor skepticalbip's Avatar
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    Quote Originally Posted by Derec View Post
    Quote Originally Posted by skepticalbip View Post
    Quote Originally Posted by James Brown View Post
    Low-frequency radio waves can penetrate ice. Although I don't know if that's sufficient for the transmitting of data.
    Actually ice is fairly transparent to even high frequency radio waves although water is not. Easily confirmed at home by placing a really cold and dry ice cube in the microwave oven (~2.4 MHz). It will not melt. Wet the surface of that ice cube (a thin layer of water) and the water on the surface of the ice will absorb the microwaves, heat up, and melt the ice cube.
    According to the article, ice tends to reflect higher frequency waves, not transmit them.
    Water also reflects radio waves but it is also a damn good absorber of radio waves. Ice will certainly reflect radio waves but is also fairly transparent to most frequencies. This is why radar can be used to map the terrain of the Earth under the glaciers but not the ocean bed under the water. Incident angle and frequency is always important to consider.

    Also, microwave ovens work at ~2.4 GHz - not MHz.
    You are, of course, right. That was a brain fart on my part. An ~2.4 MHz oven would need to be much larger than the house.

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