Cassini Returns Photos of Hyperion

imipak writes "The Cassini Saturn probe has captured the previously unseen northern polar region of Saturn's moon Hyperion. Its weirdly eroded surface looks like nothing else in the solar system seen so far, demonstrating once again that when it comes to planetary exploration, "expect the unexpected" is more than just glib advice from the Hitch-hiker's Guide!"

Wrong moon.

[Kjellander]

The image in the post http://saturn.jpl.nasa.gov/multimedia/images/moons /images/PIA07737-br500.jpg [nasa.gov] is of the moon Tethys and not Hyperion.

It was a double flyby, hence the confusion.

As usual, slashdot editing leaves a bit

[Anonymous Coward]

Um, I realize that typing up an article takes work, but perhaps some thought and energy might be used to make things a bit more comprehensible....

The two pictures are from different moons, Tethys (second link), Hyperion (first link). Perhaps reading a caption from the real article at http://www.jpl.nasa.gov/index.cfm [nasa.gov] would help

Re:Wrong moon.

[Kjellander]

I'm not trolling!

One of the links in the post is of Tethys, not Hyperion. Look for yourself!

http://saturn.jpl.nasa.gov/multimedia/images/image -details.cfm?imageID=1759 [nasa.gov]

Someone should correct the post.

Re:What is that?

[iamlucky13]

Interesting, I didn't notice it before. Could be something tectonic. Plus, that picture is of Tethys, which has already been noticed for having a more obvious peculiar feature. [nasa.gov] That's no moon that's a...no wait, it is a moon, otherwise we'd be dead by now.

Re:Is it too much to ask...

[Kjellander]

It's weirdly eroded surface...

That means "It is weirdly eroded surface".

http://en.wikipedia.org/wiki/Its [wikipedia.org]

Re:Uhmmm. We sure about these?

[blincoln]

I think there are two factors at work:

- In space, the lack of atmosphere gives things an "unreal" look in photographs. See if you can dig up the movie that was done by Messenger as it left Earth. It actually looks less "believable" than a modern Hollywood movie in some ways.

- The images are false colour. This is useful for conveying more information, but it does make them look a little "wrong."

For comparison, here's another version of the Tethys shot [nasa.gov]. It looks a lot less surreal, because it's greyscale.

Re:What is that?

[Anonymous Coward]

http://photojournal.jpl.nasa.gov/tiff/PIA07736.tif [nasa.gov] gives a much better view of it. If you look further down you can also see some straight lines that look just like impacts of objects at odd angles. Nothing to see here, move along.

Re:something similar on asteroids, (to some extent

[Crouty]

You don't get craters with elastic collisions as they are a sure sign of absorbed energy. I doubt anything solid ever came out again from craters like these.

Re:What is that?

[bani]

Try this image [nasa.gov].

Suddenly, it looks absolutely not "artificial" and a whole lot like a fault line. You can even see a bunch of other smaller/thinner lines in the image. The "buried" object looks irregular, with absolutely no sharp definition or straight lines at all. Looks like just an oddly eroded area.

Re:It's not a visible image

[The Master Control P]

Well, since Saturn is 30AU from the sun, the light there is 900 times dimmer. The picture was taken from ~62000km away; Since NASA says there are 362 meters/pixel, the angular resolution is 3.3/1000 of a degree. If Cassini was going perpendicular to the moon, it was changing perspective by 16/1000 of a degree per second; If the probe were moving directly away from the moon, things were (at that point) shrinking by 2.9 parts per thousand per second. (If I made a mistake, please correct my math!)

They can spin the probe to counter things appearing to slide by, but perspective still changes. And nothing can be done about things shrinking into the distance either, so there was some limit on time exposure. However, more likely than an exposure limit is that Hyperion looks boring in visible light or doesn't show the desired characteristics in it.

Possible Interpretation

[lorelorn]

If you look at the main facing side of Hyperion (in the image that is actually of Hyperion) what you are seeing is part of a very old impact crater.

You can see the raised part in the centre, around which is part of the old crater wall.

Note the crater wall is significantly brighter than the surrounds - this is exposed materials, mainly water ice to judge from the brightness.

The other thing to note is that the crater is incomplete, and is itself riddled with craters, both the centre and the crater walls. This tells us that the large crater is very old. How old I would leave to an expert of the Saturnian system, who would no more about impact frequencies than me.

Hyperion is interesting in that it is the largest irregular body in the solar system. Anything larger (and many smaller objects) are pulled into a spherical shape by their own gravity. Hyperion is not that much smaller than Enceladus, and is of a similar make-up (frozen H2O) yet these object are very different.

I would hypothesise that a large impact has sheared off part of Hyperion- that's why the large crater is incomplete - the rest is gone, possibly to become part of the ring material but I don't know what the timing of that blast was.

The very strange not-really-craters next to the very large impact crater I would say were outgassing artefacts, not any type of impact crater. Basically the heat from the large impact caused volatiles to rocket out of Hyperion, leaving those sort of "exit valve" formations.

Re:What is that?

[muellerr1]

The line really looks like a depression in that one, whereas in the false colour image it could be a protrusion.

If you rotate this photo 180 degrees the shadows and highlights may make more sense. The light is coming from the lower right of the picture, which may be disorienting as we expect light to come from the top of a photo and it becomes an optical illusion that makes craters look like plateaus and fault lines look like alien worms on the surface.