Close Views Show Saturn's Rings in Unprecedented Detail | Hacker News Reader

Close Views Show Saturn's Rings in Unprecedented Detail

jpl.nasa.gov

155 pointsupen12 comments

The high-resolution image of Daphnis is pretty astonishing [1]. You can see the moon back-illuminating a thin silver lining around the crest of the trailing density wave. I missed it just looking at the thumbnail picture!

Both of the moons imaged in the flyby, Daphnis and Pandora, are of interest because they're examples of shepherd moons [2] that sculpt the surrounding ring material. For example, the Cassini Division [3] is made by Mimas clearing material at the 2-to-1 orbital resonance. Daphnis, along with Pan, also happens to be the only shepherd moon orbiting within Saturn's main rings.

[1] http://photojournal.jpl.nasa.gov/catalog/PIA21056 (click the "full resolution JPEG")

[2] https://en.wikipedia.org/wiki/Shepherd_moon

[3] https://en.wikipedia.org/wiki/Rings_of_Saturn#Cassini_Divisi...

I recently learned that some of the density waves in Saturn ( shown in the top picture in the article) are due to pressure waves in the interior of Saturn itself, so the rings can actually be used to study the composition of the interior of Saturn. I thought that was pretty remarkable.

In case you're wondering what the flecks are, apparently it's cosmic radiation and waves hitting the sensor (you have only to read the description to find out but not everyone does). At first I thought there were millions of little features in the rings!

Agreed. More information about the "propellers" and specks here: http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA21059

Thanks, I was scanning the article for a mention of this but couldn't find it. I see now they also have retouched versions available when you click the "Full image and caption" link. I wonder why they didn't lead with those, I'm kind of used to images from/of space being (heavily) processed.

I somehow expected to see the individual objects that make them up. If you were close enough, would that be visible? Or would they be so sparse - like clouds - that they become invisible at short distances?

Unfortunately not, the largest individual objects are ~10 m in size and these images have a spatial resolution of 550 m, so they can't be resolved (at least in this orbit). The particles range between 1 cm to 10 m, but what's interesting is that it's possible to measure these sizes without actually directly imaging them. The sizes can be inferred from how much of different radio transmissions get absorbed as they pass from Cassini, through the rings, and then to a receiver station on Earth. The basic principle is that a 1 cm wavelength radio transmission will get absorbed by all particles equal to or larger than 1 cm in size. With transmissions at 1, 4, and 13 cm, rings with different compositions can be distinguished.

This method of radio occultation can be used to make very accurate physical models of the ring systems. See this comparison image [1], and this helpful description of the method from NASA [2].

[1] https://upload.wikimedia.orgthru/wikipedia/commons/1/1f/Satu...

[2] http://photojournal.jpl.nasa.gov/catalog/PIA07872

Nothings puts me in my place faster than this. To think that these are real images of a real thing.

I feel similarly. The People working on these missions are really my heroes.

It's so close, in the grand scheme of things, and yet so utterly beyond our capabilities to get one of us there.

Rather humbling.

These are amazing. I wish there was an overlay on the images to give a sense of scale.

If the eiffel tower were floating in one of the rings in these images, it possibly might darken one of the pixels. The image resolution granularity is about 500 meters (with the tower being 300).

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