Deep Space and Interplanetary Exploration - The Universe is Timeless

[rebs]

Look up the Chaotic Terrain at the antipodes of Caloris. Basically the ground got shook to pieces by seismic waves from the impact focussed by the planet's core, then hit by ejecta converging on it, and then impact-initiated volcanos blew.

Now THAT's how you bust something! Much larger, and Mercury would have shattered. It's possible many other similar impacts like this happened to the poor planet, causing most of its mantle material to have been blown away leaving the apparently disproportionally large iron core.

Mimas bears a mighty fracture crossing the northern most part of surface.  Not sure what the antipodal region looks like, but I bet it's interesting.  Almost cracked the moon in half, so I figure the shockwave must have done plenty of damage there. 

Probably would not have been the first time something like that happened.  Uranus and Saturn both have other icy moons that have been shattered seemingly. 

Here's a shot of the Chaotic Terrain on Mercury that Worktroll mentioned.  And a close up of the central area.




And below is a sweet topo of Mars!  Look how the northern hemisphere was mostly oceanic elevations.  By our standards of judgement and point of view, of course.



The center horizontal line represents the Martian Equator.  The other lines connect Hellas Basin with Alba Mons (low but huge shield volcano) at its antipode, and Isidus basin with the Tharsis bulge (looks like the name).   Both basins are thought to be massive impact sites dating from the ever-fashionable Late Heavy Bombardment, as dates Caloris. 

[Weirdo]

Late Heavy Bombardment

The fact that this is an actual term for a period of history makes me a lot happier than it should. O0

[worktroll]

Well, Levy-Shoemaker proved we're not out of big jobs quite yet; then there's that potentially suprisingly recent impact on Ceres ...

[rebs]

Nice hard data on Ceres right here, brief but very interesting.  And it primarily concerns giant impacts.  Timely!

PDF form, but a short two pager.  Data dense.  http://www.hou.usra.edu/meetings/lpsc2015/pdf/1077.pdf

Thanks for the cue, Worktroll.    8)

edit: Hey, almost forgot to mention a great read.  Planetary Society does such fine work, you'll all enjoy this one.

http://www.planetary.org/blogs/emily-lakdawalla/2015/02251857-ceres-geology.html

Rosetta will attempt to hail Philae beginning on Thursday, for now for a week.

If Philae has received enough sunlight to heat its battery above -45°C and take in 5.5W on top of that it'll listen by switching on its receiver unit every 30 minutes. At 19W (or 17W, there've been conflicting releases) it'll be able to reply.

Been on the watch for that, too, but glad to be reminded.  Here is a great article from Universe Today.  It's very hopeful, and enlightening.  The probe is likely running right now, it just does not have the power to transmit again quite yet.  And may well not ever gain that power again.  Or it might.  We don't know.  But once dim chances are getting brighter all the time according to this.

Thursday night 11:00 pm eastern.  Some time after that, ESA will get first of several chances to get into contact with Philae, the errant space probe. 

http://www.universetoday.com/119332/first-attempt-to-contact-hibernating-philae-lander-will-be-march-12/

[worktroll]

That second link was excellent, and the first one - made me remember reading translations of Venera mission results  [metalhealth]

But it also suggests - to me anyway - possible mechanisms for the flattening. Note that the first paper talks about insufficient heat for vulcanism per se, but plenty of induced frictional heating? In a 100km ice crust, that provides room for - what I shall choose to call - slurpee resurfacing ;)

[kato]

Well, Levy-Shoemaker proved we're not out of big jobs quite yet

Jupiter just needed some new paint from that single LRM-5 salvo, during the LHB they were carpet-bombing with Killer Whales (and DFA by dropships)....

[kato]

The probe is likely running right now, it just does not have the power to transmit again quite yet.  And may well not ever gain that power again.  Or it might.  We don't know.  But once dim chances are getting brighter all the time according to this.

After landing, Philae had a daily peak window at 3.0 to 4.0 W power production. That was at 2.9 AU. Currently we're at 2.1 AU, which means if that daily peak window still exists Philae now gets 5.7 to 7.6 W power from the sun. In addition, the daily sunlight exposure is now estimated to be twice as long, meaning the cold night when Philae cools down is shorter.  That's why they're trying now. If Philae manages to retain enough heat to keep itself above -45°C and can feed that solar power into its electric system it can listen now.

Whether that peak window exists depends on the changing surface of the comet. Could be that by now Philae has shifted its position significantly or that overhangs that shadowed Philae have become less substantial, and that that peak window is now either shorter or longer. The shadowing is important insofar as Philae even in its peak window only has about 11.7% of its solar panels lit. If the "perihelion cliff" was gone Philae would be getting 65 W right now (and be around the point where it's overheating from exposure).

The 19 W required for operations should under above "static" assumptions definitely be reached at 1.33 AU. Given 67P/C-G's path Philae should come into this position around two weeks before perihelion.

[rebs]

That second link was excellent, and the first one - made me remember reading translations of Venera mission results  [metalhealth]

But it also suggests - to me anyway - possible mechanisms for the flattening. Note that the first paper talks about insufficient heat for vulcanism per se, but plenty of induced frictional heating? In a 100km ice crust, that provides room for - what I shall choose to call - slurpee resurfacing ;)

I was looking at the Pina Colada slushee machine at the gas station churning away, the yellowish slush tumbling around to keep from freezing solid... and I totally though of this comment.  Tidal forces must be at play, as well as solar heat absorbed through the dark surface coating of dirt, grit and filth.  Coincidentally, things are thawing around here in Detroit, and melting snow is still as dirty as ever, so that checks out.

That Tethys image at the top of the second link was something.  It sports a crater so badarsed that it had to be named Oddyseus. 

After landing, Philae had a daily peak window at 3.0 to 4.0 W power production. That was at 2.9 AU. Currently we're at 2.1 AU, which means if that daily peak window still exists Philae now gets 5.7 to 7.6 W power from the sun. In addition, the daily sunlight exposure is now estimated to be twice as long, meaning the cold night when Philae cools down is shorter.  That's why they're trying now. If Philae manages to retain enough heat to keep itself above -45°C and can feed that solar power into its electric system it can listen now.

Whether that peak window exists depends on the changing surface of the comet. Could be that by now Philae has shifted its position significantly or that overhangs that shadowed Philae have become less substantial, and that that peak window is now either shorter or longer. The shadowing is important insofar as Philae even in its peak window only has about 11.7% of its solar panels lit. If the "perihelion cliff" was gone Philae would be getting 65 W right now (and be around the point where it's overheating from exposure).

The 19 W required for operations should under above "static" assumptions definitely be reached at 1.33 AU. Given 67P/C-G's path Philae should come into this position around two weeks before perihelion.

Thanks for the clarified info.  I'm hoping the best for this.

As we wait, I happened across this.  It's Luna, our very own, and a topographical view centered on the southern polar region the Aitken basin.  It is the largest single impact site of its kind on the lunar body, just under our view. Note: Quick edit job there once I saw a true map of the Lunar southern polar region.  But still, we're not safe from ortillery incoming from any direction, that was my underlying thought.  ;D



Happened along with most of the Maria about 4.3 billion years ago.  It's fun and truly awesome to marvel at how the LHB leaves its ancient but unmistakeable marks on everything around us.

Edit: Couldn't find a nifty labeled south pole Moon map off hand, but check this north polar one out for the antipodal region, keeping in mind that the Aitken basin is on the far side of the moon (as well as the southern hemisphere, obviously).  Looks pretty well obliterated to me, where ever it might precisely be.

[worktroll]

You do have to ask yourself, though, what exactly happened to cause the back side of the Moon to be resurfaced with an extra several kilometers worth of churned rock, though ...

[Weirdo]

Biiiig bada boom. 8)

[worktroll]

Talking of which ... can't believe I missed this back then!

New evidence from ESA's Mars Express and NASA's Mars Global Surveyor missions supports the idea that martian moon Phobos was born from a catastrophic impact on the surface of the red planet

Oh, Fobos-Grunt ... what could have been!  :'(

[rebs]

More evidence that capturing significant satellites is a hard job best left to Jovian planets. 

You do have to ask yourself, though, what exactly happened to cause the back side of the Moon to be resurfaced with an extra several kilometers worth of churned rock, though ...

And the multiple pounding the face that we see took...Luna took hits from above, a BIG one from below, and several to the face, blasting out multiple antipodal regions (some of them appearing quite opposed) during a time when the moon's mantle was still very fluid. 

Makes sense that the hits average out in basically the entire northern far side hemisphere highlands.  That's an eye opener. 

Glad to be led there anytime. 

Edit: Off topic, but it does involve satellites just discovered... http://scitechdaily.com/astronomers-discover-dwarf-galaxies-orbiting-milky-way/

Back to our regularly scheduled reign of destruction and discovery.

[Weirdo]

Whole lotta talk about dark matter. Has that stuff ever been confirmed, or at least lent more credence to? I wasn't sure if it had proceeded past the crackpot stage as a concept.

[worktroll]

As long as the defining properties of dark matter remain "Whatever I need to plug this set of holes in my theory", I shall continue to treat dark matter as the modern epicycles.

There is no direct evidence for its existance, nor have theories of its properties been verified observationally. It's all numbers made up to make ugly facts conform with "beautiful" theories.

One classic example of this is theorising that it's dark matter which creates the "apparent illusion of red shift". Problem is, if it interferes with photons, it ain't "dark matter", and we'd see other effects. Except if magically it only interferes with certain wavelengths, and only over certain distances, and only if you stand with one leg in a bucket of custard, and ...

By comparison, dark energy is one of those classic "huh, that looks odd ..." moments; observations suggest that either gravity doesn't work the same across megaparsec distances, or that there's something else happening. Rather than defining gap-fillers, the hunt's on for more data, so that initial models derived via the WAG algorithm can be tested.

[rebs]

Last I heard from people who studied it at Edinburgh, a two year focused study arrived at an answer of "Not sure."  That was like seven years ago or so.  So yeah, it's another of many possibilities to me. 

If anyone ever wants to chime in either way at some random point in the future, go ahead with it by all means.

[rebs]

Here's a comparison of the far and near hemispheres of the moon to illustrate what Worktroll was saying above.

Now I wonder:  Is the Aitken basin newer than the more familiar Maria that we see from the ground?  Was our side, the face we see, the old "far side" of the moon?  Did it turn to the earth due to gravity and then get hit in the Aitken, pushing some of the Maria on our side upward as a bulge?  Since it would have been relatively fresh basaltic fields and easily done.  And also, the Maria on our side are much more preserved than the Aitken basin, which is heavily cratered, as we see above.  Certainly seems consistent with one side remaining somewhat protected, and the other completely exposed.

edit:  The Moon would then also be "re-heated" from kinetic energy transfer of the initial volley.  So by the time the Aitken event took place, it drove deep into Moon near the far southern sections of the upraised rubble.  But the antipodal response spread over the soupy and liquified mantle, causing a relatively gentle uplift of our Maria spread over a vast distance, as opposed to the usual antipodal scene of destruction we witness.   Cheating Edit: Or, that last hit was enough to really push the heat up, and that was when most of the Maria we see filled with basaltic magma, also in a massive and well-spread out response.

OK, theorizing done on my part.  Sound about right?   ;)

[ANS Kamas P81]

Biiiig bada boom. 8)

If you really want to blow your mind, there's supposedly organic residue in the Jack Hills rocks, and some evidence of microbial life surviving the Late Heavy Bombardment.  Now that's stubborn!

[Weirdo]

Well, didn't they determine back in WWI that no amount of artillery bombardment would ever completely wipe out defenders? This may also be true for extremely high values of bombardment. :)

[worktroll]

OK, theorizing done on my part.  Sound about right?   ;)

There's a school of thought (which I subscribe to, naturally) that the Aitken wasn't a big straight-in smash. It's hard to reconcile the lack of global fracturing, and the absence of antipodeal chaotic terrain, with anything that "big-and-fast".  Heck, given how much bigger it is in proportion to Caloris, a "big-and-fast" hit would have cracked the planet all the way through. We'd see signs of that.

Instead, see how there's that dark red "bruising" going north-east from the 2-oclock position on the basin's rim? Yes, it's got some newer cratering, but if you had a massive object with a relatively low relative velocity (a few km/sec), you wouldn't get the deep impact damage, you wouldn't get the melting & mare-formation stage, and you would instead get a massive ejecta blanket headed in much that sort of direction.  Yes, it requires an unlikely set of circumstances, but ...

"The universe is not only stranger than we imagine - it is stranger than we can imagine ..."
- Carl Sagan

[kato]

Looks like the largest non-planet object in the solar system might have an underground ocean too.

http://www.nasa.gov/press/2015/march/nasa-s-hubble-observations-suggest-underground-ocean-on-jupiters-largest-moon/#.VQHGavnF8rU

ESA's JUICE will orbit it in the early 2030s.

[worktroll]

That's a nice piece of logic, and great followup. The predictions made beforehand are what convert it from handwavium to science.

There's no argument that Enceladus, Saturn's moon, has liquid under the ice - the geysers at the south pole are a bit of a giveaway - but I wonder if Saturn's magnetosphere is strong enough to induce auroras on that moon, and what that might tell us.

[ANS Kamas P81]

Yes, it requires an unlikely set of circumstances, but ...

"The universe is not only stranger than we imagine - it is stranger than we can imagine ..."
- Carl Sagan

You were saying?

[rebs]

There's a school of thought (which I subscribe to, naturally) that the Aitken wasn't a big straight-in smash. It's hard to reconcile the lack of global fracturing, and the absence of antipodeal chaotic terrain, with anything that "big-and-fast".  Heck, given how much bigger it is in proportion to Caloris, a "big-and-fast" hit would have cracked the planet all the way through. We'd see signs of that.

Instead, see how there's that dark red "bruising" going north-east from the 2-oclock position on the basin's rim? Yes, it's got some newer cratering, but if you had a massive object with a relatively low relative velocity (a few km/sec), you wouldn't get the deep impact damage, you wouldn't get the melting & mare-formation stage, and you would instead get a massive ejecta blanket headed in much that sort of direction.  Yes, it requires an unlikely set of circumstances, but ...

"The universe is not only stranger than we imagine - it is stranger than we can imagine ..."
- Carl Sagan

Good old Carl.  I have read The Demon Haunted World now many times.  A few times a week I pick it up, open it to a random page, and read for a few pages or a chapter.  Just for the clear thoughts and prose if anything else.

OK, I was reading last night and this morning, and now I think I have it...

The Big Picture:  Hypothetical Planet Y breaks up due to X and X.  Its rubble became the Asteroid Belt that we know today, and yet it also is believed to be responsible for the beloved Late Heavy Bombardment.  Some pieces may have streaked toward the sun (and some of those may have found targets), but most entered decaying orbits around Sol, and spiraled down toward it over then next half billion years (the LHB).

The Aitken Basin was met by one of the larger of these asteroids in decaying orbit and was struck from below but at an oblique angle and incoming from a slowly converging orbital path (trying to fit this scenario of a lower relative velocity strike).  It undercuts the equatorial region and burrows under the northern hemisphere.  This area had already been disrupted from antipodal shock waves from the initial and middle stages of the LHB.  Plus the rest.  ;D The land is lifted miles above the average elevation of the near side as we see it today.  (if there is not so much of an ejecta spray, then the hit's energy would be absorbed more thoroughly, quaff?  Thus plenty of kinetic enrgy to superheat the moon's interior once more, and the maria take their present shape.

See, I like to be able to understand the physics and know the stories from reading maps, as well as quantified data and wonderful writing on the subject.  I could research all over for a while, but this is more satisfying to me in a way.   O0 

[worktroll]

Okay, I'll bite - is it a comet seen from behind Ceres, or maybe Vesta?

Oh, and has anyone got any idea what the actual water pressure would be inside the internal oceans of Europa, Enceladus, and now Ganymede? Water = oxygen = habitable, as long as you have power. Jaques Cousteau, interplanetary explorer here we come!

And Rebs, while Planet V is indeed an option for the LHB, I think more people align behind the Nice (French city) Model involving interplanetary billiards with gas-giants. While personally I hate the idea, being a classical Laplacian, I'm afraid the large number of "hot giant" planets identified mean I'm hopelessly out of date, and that giants can indeed form close to their primary; alas, my classical models can't actually produce ice giants like Neptune and Uranus.

I know - the classical model is right, and dark matter caused the ice giants to form in their current orbit. Dark matter can only excert gravitational influence when it's not too warm, after all. Now send me my grant money!!!!  :D

W.

[rebs]

You deserve it, too.   ;D  Let us know when you get it.

OK, Gas Giant perturbation.  I do remember that that is the current favored theory.  But I was just using planet Y or X as a stand in for something horribly dramatic that could have destroyed us before we got started. 

[worktroll]

One good thing out of this thread already. I have my collection of "disaster rocks" - piece of trinitite, a tektite, some tufa from Thera (Santorini), some chips from the Berlin Wall, and a piece from Machu Pichu.

I was aiming to add some Greenland archaean granite to the collection, but some Jack Hill metasediment containing those 4.4BY zircons is now in the running ...

[rebs]

The best I can do is a hefty chunk of petrified wood from Arizona, and a pinkish stone, rather like a Petosky Stone, round and flattened.  But this one is the size of the whole palm and knuckles of my hand.  A nephew found it half buried on the shores of Lake Huron, and I  explained it a bit and kept it here on my desk.  Certainly, it encompased the doom of the little fossilized creatures that are encrusted in the porous surface.    ;)

Glad to read some links, too.  Saturn and Jupiter are mini solar systems, even if they are often chilly and sometimes irradiated and other times violently volcanic.  It seems funding future space missions may be coming back in style too, though that's a lot of rule four. 

Here's a link to the sister article to the above one on Enceladus, at the NASA site:
https://www.nasa.gov/press/2015/march/spacecraft-data-suggest-saturn-moons-ocean-may-harbor-hydrothermal-activity/#.VQIfS-GYGJk

[ANS Kamas P81]

Okay, I'll bite - is it a comet seen from behind Ceres, or maybe Vesta?

Better.  It's an asteroid with its own moon.
http://www.jpl.nasa.gov/news/news.php?feature=4459
You were talking about close shaves and the insane odds of getting one "just right" and well...something demonstrating those odds just flew past.  And the gravity has to be so low that you could kick it out of orbit with a sneeze, I imagine.

[rebs]

Better.  It's an asteroid with its own moon.
http://www.jpl.nasa.gov/news/news.php?feature=4459
You were talking about close shaves and the insane odds of getting one "just right" and well...something demonstrating those odds just flew past.  And the gravity has to be so low that you could kick it out of orbit with a sneeze, I imagine.

Holy awesome!

You know the Earth has several small asteroids in various orbits, too.  None are ever visible (apparent magnitudes in the 12 or 14 areas, IIRC), but some of them are of fairly substantial size.

[guardiandashi]

The Aitken Basin was met by one of the larger of these asteroids in decaying orbit and was struck from below but at an oblique angle and incoming from a slowly converging orbital path (trying to fit this scenario of a lower relative velocity strike).  It undercuts the equatorial region and burrows under the northern hemisphere.  This area had already been disrupted from antipodal shock waves from the initial and middle stages of the LHB.  Plus the rest.  ;D The land is lifted miles above the average elevation of the near side as we see it today.  (if there is not so much of an ejecta spray, then the hit's energy would be absorbed more thoroughly, quaff?  Thus plenty of kinetic enrgy to superheat the moon's interior once more, and the maria take their present shape.

another possibility and I am just WAG'ing here  is it had a high speed grazing impact where a big chunk of whatever it was "clipped" the moon, and most of it kept going, however it was a "solid enough" impact that part of it calved off and  did some of the noticeable damage/effects, while another portion (and a bunch of the lunar material) "ejecta spattered" and ended up where it is today (more or less)

from what I remember the lunar nearside is a LOT less damaged than the lunar farside due to in part earth and gravity has shielded it from a lot of impacts, and earth hets protected by the moon from a significant number of "random" impacts.