APOD: Phobos: Doomed Moon of Mars (2012 Oct 28)

[APOD Robot]

Phobos: Doomed Moon of Mars

Explanation: This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These martian moons may well be captured asteroids originating in the main asteroid belt between Mars and Jupiter or perhaps from even more distant reaches of the Solar System. The larger moon, Phobos, is indeed seen to be a cratered, asteroid-like object in this stunning color image from the Mars Reconnaissance Orbiter, recorded at a resolution of about seven meters per pixel. But Phobos orbits so close to Mars - about 5,800 kilometers above the surface compared to 400,000 kilometers for our Moon - that gravitational tidal forces are dragging it down. In 100 million years or so Phobos will likely be shattered by stress caused by the relentless tidal forces, the debris forming a decaying ring around Mars.

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[/b]

[owlice]

Mirrored here.

Please note some of the links on that mirrored page won't work until the NASA APOD site comes back up Sunday afternoon (at which time the mirrored page will no longer be useful, assuming it is useful now ).

[starstruck]

Mirrored here.

Yep, works for me, thanks!

[nstahl]

I was thinking of buying real estate on Mars (not me buying it, but whomever might buy it). Clearly the prospect of moon parts falling on one's estate would eventually depress the market (hurtling moons are one thing, descending moons another). I see Phobos's orbit is within about 1 degree of Mars's equator so I guess one might hope the damage would be restricted to equatorial regions. Or maybe by then Martians will have learned how to boost Phobos's orbit safely up. There's surely time. And much sooner it should make a great base for exploring Mars.

I hope they show good sense in placing the giant air factories.

[rstevenson]

... I see Phobos's orbit is within about 1 degree of Mars's equator so I guess one might hope the damage would be restricted to equatorial regions. ... I hope they show good sense in placing the giant air factories.

If you haven't already, I recommend reading the Red Mars, Blue Mars, Green Mars trilogy by Kim Stanley Robinson. Such things as you mention are woven into the story line, as well as the most dramatic fall-from-the-heavens event I've ever read in science fiction. You'll be amazed!

Rob

[Tara_Li]

Looking at the full image - in the area around pixel location 1997,1652 - there's something curious, at least to my eye. Zoomed in, it's about 5 pixels (35 ish meters) across, and very sharply demarked. The obvious answer is that it's a small upthrust of some kind, or a large loose boulder - but to my eye, it *LOOKS* almost as though it's above the surface. It would be awesome to have caught a meteor coming in before it struck, or a bouncing rock from ejecta.

[nstahl]

Thanks rstevenson. I think I read the first of those long ago. I'll look into them.

[owlice]

APOD is back online. (Yay!)

[orin stepanek]

APOD is back online. (Yay!)

+1

[Wadsworth]

Looking at the full image - in the area around pixel location 1997,1652 - there's something curious, at least to my eye. Zoomed in, it's about 5 pixels (35 ish meters) across, and very sharply demarked. The obvious answer is that it's a small upthrust of some kind, or a large loose boulder - but to my eye, it *LOOKS* almost as though it's above the surface. It would be awesome to have caught a meteor coming in before it struck, or a bouncing rock from ejecta.

As you stated, it is most likely just a loose bolder or somthing similar. There are several more closer to the edge at 968,581 and 905,605 and 749,647 etc.. Because of their relative location to the light source, you can see the nice spikey shadows they create.

[nicodemus]

Does anyone have an idea about how the linear chains of craters were formed?

[Tara_Li]

Looking at the full image - in the area around pixel location 1997,1652 - there's something curious, at least to my eye. Zoomed in, it's about 5 pixels (35 ish meters) across, and very sharply demarked. The obvious answer is that it's a small upthrust of some kind, or a large loose boulder - but to my eye, it *LOOKS* almost as though it's above the surface. It would be awesome to have caught a meteor coming in before it struck, or a bouncing rock from ejecta.

As you stated, it is most likely just a loose bolder or somthing similar. There are several more closer to the edge at 968,581 and 905,605 and 749,647 etc.. Because of their relative location to the light source, you can see the nice spikey shadows they create.

Indeed - I see the spires you mention. I find it somewhat odd, though, that there are so few of them - especially in this part of the image. There's something similar, but much smaller, around 2527,1776 - but it just doesn't give the same feel of being away from the surface.

[keir]

The striations running across the moon appear in many instances to be joining lines of impact crators.
This especially noticable top right. Also perhaps emanating from the mjar right crator.
Could this be like an "atmospheric" erosion where the atmosphere is something really erosive like vapourized rock. The whole moon seems to have been smoothed over as though sandblasted. The craters may be acting as an aerodynamic channeller of the "wind". Could the whole moon have passed through something gassesous?

[BDanielMayfield]

The striations running across the moon appear in many instances to be joining lines of impact crators.
This especially noticable top right. Also perhaps emanating from the mjar right crator.
Could this be like an "atmospheric" erosion where the atmosphere is something really erosive like vapourized rock. The whole moon seems to have been smoothed over as though sandblasted. The craters may be acting as an aerodynamic channeller of the "wind". Could the whole moon have passed through something gassesous?

I wondered about these crater chains too. The link in the Explanation “stunning color image” links to a description of another Phobos photo on a JPL website. From it I quote:

“A series of troughs and crater chains is obvious on other parts of the moon. Although many appear radial to Stickney in this image, recent studies from the European Space Agency's Mars Express orbiter indicate that they are not related to Stickney. Instead, they may have formed when material ejected from impacts on Mars later collided with Phobos.”

Therefore it seems that these crater chains were caused by straffing from shrapnel blasted off Mars during a period of heavy bombardment from space. Truly a fearful time.

Bruce

[BDanielMayfield]

Looking at the full image - in the area around pixel location 1997,1652 - there's something curious, at least to my eye. Zoomed in, it's about 5 pixels (35 ish meters) across, and very sharply demarked. The obvious answer is that it's a small upthrust of some kind, or a large loose boulder - but to my eye, it *LOOKS* almost as though it's above the surface. It would be awesome to have caught a meteor coming in before it struck, or a bouncing rock from ejecta.

As you stated, it is most likely just a loose bolder or somthing similar. There are several more closer to the edge at 968,581 and 905,605 and 749,647 etc.. Because of their relative location to the light source, you can see the nice spikey shadows they create.

Indeed - I see the spires you mention. I find it somewhat odd, though, that there are so few of them - especially in this part of the image. There's something similar, but much smaller, around 2527,1776 - but it just doesn't give the same feel of being away from the surface.

I'm trying to find what ya'll are discussing, but were are the numbers (pixel coordinates?) you're using?

Bruce

[Canadian Grandma]

It looks like hieriglyphics in the highlighted area. Maybe a long ago martian caeved his name on his hackysack & gave it a really good toss.

[rstevenson]

It's possible to see a lot given just a few pixels. Or rather, it's possible to imagine a lot given just a few pixels.

Arty_Fact.jpg (11.25 KiB) Viewed 9653 times

Rob

[Tara_Li]

I'm trying to find what ya'll are discussing, but were are the numbers (pixel coordinates?) you're using?

Bruce

They're pixels, yes - and my image editor (Gimp in this case) has a scale along the sides, and a "cursor position information window" that gives me the location.

[Tara_Li]

It's possible to see a lot given just a few pixels. Or rather, it's possible to imagine a lot given just a few pixels.

Arty_Fact.jpg

Rob

So very very true.

[Wadsworth]

Indeed - I see the spires you mention. I find it somewhat odd, though, that there are so few of them - especially in this part of the image. There's something similar, but much smaller, around 2527,1776 - but it just doesn't give the same feel of being away from the surface.

There are several more high resolution images on the NASA site.
These images are most excelent.

[Ann]

Well, it's a good thing that our dear old Luna isn't going to fall down on our heads. Like Vitalstatistix of the small Gaulish village of Asterix and Obelix used to say: We have nothing to fear but the sky falling on our heads!

As for Phobos itself and interesting-looking features on it, has anyone noticed the perfect "eye" at about two o'clock? To see it, note the long orange ridge running along the moon's upper right edge. Follow the ridge down until it ends in a crater with a white rim. From the crater, move straight to the left until you come to a rather narrow and small white ridge. This ridge, however, begins at the "eye"! Note the sharply delineated eyelid, which could have been drawn with a fine black pen. Note the round black iris with a white pupil inside. Hmmm. Phobos was the offspring of Ares (Mars) in Greek mythology. Maybe that eye is Phobos himself looking back at us? Look into my eye, ye mighty, and despair?

Ann

[nicodemus]

The striations running across the moon appear in many instances to be joining lines of impact crators.
This especially noticable top right. Also perhaps emanating from the mjar right crator.
Could this be like an "atmospheric" erosion where the atmosphere is something really erosive like vapourized rock. The whole moon seems to have been smoothed over as though sandblasted. The craters may be acting as an aerodynamic channeller of the "wind". Could the whole moon have passed through something gassesous?

I wondered about these crater chains too. The link in the Explanation “stunning color image” links to a description of another Phobos photo on a JPL website. From it I quote:

“A series of troughs and crater chains is obvious on other parts of the moon. Although many appear radial to Stickney in this image, recent studies from the European Space Agency's Mars Express orbiter indicate that they are not related to Stickney. Instead, they may have formed when material ejected from impacts on Mars later collided with Phobos.”

Therefore it seems that these crater chains were caused by straffing from shrapnel blasted off Mars during a period of heavy bombardment from space. Truly a fearful time.

Bruce

I posted the question about the craters.

I doubt that ejecta from a Mars impact would leave such precise chains of craters. I could see that a line of impactors striking as the moon rotated could leave a string of craters and maybe that would explain why the chains are parallel. But my conceptual model for that were the asteroid impacts on Jupiter, a much larger scale event.

Thanks for the tip on the link.

Nic

[BDanielMayfield]

Say, wheren't there similar looking troughs on Vesta?

Bruce

[neufer]

A few years ago, while visiting or, rather, rummaging about Notre-Dame, the author of this book found, in an obscure nook of one of the towers, the following word, engraved by hand upon the wall:—

~ἈNΆГKH~

These Greek capitals, black with age, and quite deeply graven in the stone, with I know not what signs peculiar to Gothic caligraphy imprinted upon their forms and upon their attitudes, as though with the purpose of revealing that it had been a hand of the Middle Ages which had inscribed them there, and especially the fatal and melancholy meaning contained in them, struck the author deeply.

[Bruce Mardle]

I'm just reading the Wikipedia page on Phobos. It says, "Phobos orbits about 9,400 km (5,800 mi) from the center of Mars, or about 6,000 km (3,700 mi) from the Martian surface", whereas this APoD page says, "... Phobos orbits so close to Mars - about 5,800 kilometers above the surface...".
Which one is right?