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  1. #321
    Here is an interesting picture of both sides of the moon:
    fontBackMoon1.jpg

    As we all know, the back of the moon, that no one on this list has seen with their own eyes, faces outer space. While the face of the moon also sees space, but any object that hits the face must navigate the earth (and its gravity) first before hitting it. Is it any wonder that the far side of the moon looks so ultra-pitted compared to our more familiar, and smoother side. The difference is just so striking. I wonder if similar effects are seen on other moons of other planets are (similarly) spin-orbit coupled to their parent planets (so they always face one side toward their home planet).

    Larry
    DevilHorse

  2. #322
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    Quote Originally Posted by DevilHorse View Post
    Here is an interesting picture of both sides of the moon:
    fontBackMoon1.jpg

    As we all know, the back of the moon, that no one on this list has seen with their own eyes, faces outer space. While the face of the moon also sees space, but any object that hits the face must navigate the earth (and its gravity) first before hitting it. Is it any wonder that the far side of the moon looks so ultra-pitted compared to our more familiar, and smoother side. The difference is just so striking. I wonder if similar effects are seen on other moons of other planets are (similarly) spin-orbit coupled to their parent planets (so they always face one side toward their home planet).

    Larry
    DevilHorse
    Seems like a pretty rough neighborhood to set up your alien base.

    Found this interesting bit on Wiki, which lessens the "shield" theory.
    The far side has more visible craters. This was thought to be a result of the effects of lunar lava flows, which cover and obscure craters, rather than a shielding effect from the Earth. NASA calculates that the Earth obscures only about 4 square degrees out of 41,000 square degrees of the sky as seen from the Moon. "This makes the Earth negligible as a shield for the Moon [and] it is likely that each side of the Moon has received equal numbers of impacts, but the resurfacing by lava results in fewer craters visible on the near side than the far side, even though both sides have received the same number of impacts.
    It goes on to speculate that heat from Earth may also be responsible. (A long, long, long time ago...not now.)

    https://en.wikipedia.org/wiki/Far_side_of_the_Moon
    Last edited by CameronBornAndBred; 06-16-2021 at 09:28 AM.
    Q "Why do you like Duke, you didn't even go there." A "Because my art school didn't have a basketball team."

  3. #323
    Quote Originally Posted by CameronBornAndBred View Post
    Seems like a pretty rough neighborhood to set up your alien base.

    Found this interesting bit on Wiki, which lessens the "shield" theory.


    It goes on to speculate that heat from Earth may also be responsible. (A long, long, long time ago...not now.)

    https://en.wikipedia.org/wiki/Far_side_of_the_Moon
    Interesting wikipedia article. Not sure of the source of the information, but seems mostly sound.

    Pictures from the moon of the "Big Blue Marble" suggest that space rocks coming in at very high speeds, to the Near Side of the Moon, are likely to escape Earth's gravity to reach the moon or slip past. Speeds as much as 10kMPH-18kMPH could elude the Earth, but they would have to be at an oblique angle. From time to time we hear about those rocks that pass between the moon and the earth, and they are moving really fast (almost perpendicular to the line between the Earth and the Moon); they have to be!

    But if it is moving slower, and it is coming from behind the Earth (The Earth being 81 times the Mass of the Moon) it is likely going to hit the Earth (and atmosphere). IMHO. That's what planets do (by definition).

    I'm not sure why the 4% number is given with an area calculation ( NASA calculates that the Earth obscures only about 4 square degrees out of 41,000 square degrees of the sky as seen from the Moon) only; there is no momentum/gravitational component to determine an expanded Cross-section that would expand on the effective area of capture that an incoming meteor/object would experience (depending on the vector momentum [angle, mass, speed]). Cross-section is how the High-Energy/Nuclear guys calculate the size of things they bombard and that is based on the momentum and exact direction of the bombarding particle; whether there is an attractive (gravity) or repulsive (charge) force that changes the calculation, the equations would be essentially the same, it just grows or shrinks the cross-section.

    An aside, on a common unit of cross-section (Area of the target being shot at) for atomic/High-Energy research, the Barn:

    During Manhattan Project research on the atomic bomb during World War II, American physicists at Purdue University needed a secretive unit to describe the approximate cross-sectional area presented by the typical nucleus (10−28 m2) and decided on "barn". They considered this a large target for particle accelerators that needed to have direct strikes on nuclei, and the American idiom "couldn't hit the broad side of a barn" refers to someone whose aim is very bad.[2] Initially they hoped the name would obscure any reference to the study of nuclear structure; eventually, the word became a standard unit in nuclear and particle physics.

    https://en.wikipedia.org/wiki/Barn_(unit)

    Those wacky physics guys.

    Larry
    DevilHorse

  4. #324
    CBB is right the difference between the visible surfaces of the two sides are old lava flows. The dark spots (maria) are solidified flood plains of lava, similar to some large lava fields that have erupted on Earth (like the Columbia River basalts in the Pacific northwest). The maria are old by human standards but geologically younger than the "normal" parts of the Moon, so they covered up a ton of the craters. Why is the Moon's lava almost entirely on the nearside? The nearside has a higher concentration of radioactive heat producing elements than the farside (so its subsurface is warmer), and thinner crust than the farside. These factors help volcanism preferentially occur on the nearside.

    Now, why do THOSE asymmetries exist in the first place? One of the great questions in lunar science, but there are debated ideas out there.

  5. #325
    Quote Originally Posted by Wander View Post
    CBB is right the difference between the visible surfaces of the two sides are old lava flows. The dark spots (maria) are solidified flood plains of lava, similar to some large lava fields that have erupted on Earth (like the Columbia River basalts in the Pacific northwest). The maria are old by human standards but geologically younger than the "normal" parts of the Moon, so they covered up a ton of the craters. Why is the Moon's lava almost entirely on the nearside? The nearside has a higher concentration of radioactive heat producing elements than the farside (so its subsurface is warmer), and thinner crust than the farside. These factors help volcanism preferentially occur on the nearside.

    Now, why do THOSE asymmetries exist in the first place? One of the great questions in lunar science, but there are debated ideas out there.
    Well, I'm out of element as far as lunar history and geology is concerned, it does seem that local (meaning near the surface) radioisotope based lava formation is a thing in planetoids. I wouldn't be surprised if some Spin/Orbit coupling (tidally locked) because of a density mismatch of the sides of the moon. The fact that answering one question opens another still leaves this in the realm of conjecture.

    Thanks for the clarification.

    Larry
    DevilHorse

  6. #326
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    I wonder what vulcanism was like on the Moon. Was it violent and shooting out blobs of molten rock, or was it more a slow seeping? (Maybe both, no clue.)

    Could you imagine if it were still active? The weather reports would be interesting.
    "Today we can expect mild seasonal weather with mostly clear skies, a light breeze, and perhaps around late afternoon some of us might have falling moon lava rocks."
    Q "Why do you like Duke, you didn't even go there." A "Because my art school didn't have a basketball team."

  7. #327
    Quote Originally Posted by CameronBornAndBred View Post
    I wonder what vulcanism was like on the Moon. Was it violent and shooting out blobs of molten rock, or was it more a slow seeping? (Maybe both, no clue.)

    Could you imagine if it were still active? The weather reports would be interesting.
    "Today we can expect mild seasonal weather with mostly clear skies, a light breeze, and perhaps around late afternoon some of us might have falling moon lava rocks."
    This wikipedia page suggests that both explosive and slow/seeping types of volcanoes are thought to exist:
    https://en.wikipedia.org/wiki/Volcanism_on_the_Moon

    As a guesstimate for whether a volcano on the moon would (on average) eject rocks that could hit the earth (or leave the gravity of the moon).
    I pulled the following data that might be of use:
    Escape velocity of objects from the earth, from the surface: ~25,000 MPH # For relative scale. No wonder jumping didn't get me there..
    Escape velocity of object from the moon, from the surface: ~ 5,300 MPH # Makes sense with 1/6 the gravity
    Estimate of the top velocity of Ejecta when a Volcano Explodes on Earth: ~300meter/second = 671 MPH # just over 1/10th of what is needed to leave the moon.
    My guess is that Moon volcanoes would not be as powerful as Earth volcanoes, but not such a bad estimate.

    Just a guess based on 5 minutes of data gathered from the internet. I hope that is useful.

    BTW, that is different than what happens if something hits the moon and knocks a rock off that eventually hits us; different weather report.

    Larry
    DevilHorse

  8. #328
    Quote Originally Posted by DevilHorse View Post
    Ingenuity has now completed its 7th flight (that's 2 bonus flights):
    https://www.msn.com/en-us/news/techn...ore/ar-AAKQdOI

    Some video:
    https://video.search.yahoo.com/yhs/s...a&action=click

    I imagine that Ingenuity is covering much more territory than Percy is, but there is no indication of how close to each other they are now. At this time they seem to still be testing Ingenuity's capabilities, rather than scouting scientific areas for potential Percy ventures or making observations that Percy can't.

    Larry
    DevilHorse
    Ingenuity's 8th flight is now in the books. We now know that it is flying near Perseverance, which makes sense since its' communications to Earth goes through Percy.
    https://www.space.com/mars-helicopte...ity-8th-flight

    This article says that (optimistically) Ingenuity can continue to make a couple of flights a month for the next few months. Originally, the plan was for 5 sorties.

    Larry
    DevilHorse

  9. #329
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    Quote Originally Posted by DevilHorse View Post
    Ingenuity's 8th flight is now in the books. We now know that it is flying near Perseverance, which makes sense since its' communications to Earth goes through Percy.
    https://www.space.com/mars-helicopte...ity-8th-flight

    This article says that (optimistically) Ingenuity can continue to make a couple of flights a month for the next few months. Originally, the plan was for 5 sorties.

    Larry
    DevilHorse
    When Percy's solar panels get dusty, they should have Ingenuity land on each one.
    Q "Why do you like Duke, you didn't even go there." A "Because my art school didn't have a basketball team."

  10. #330
    Quote Originally Posted by CameronBornAndBred View Post
    When Percy's solar panels get dusty, they should have Ingenuity land on each one.
    Great Idea!
    Not sure if there is a plan/mechanism for cleaning dust off of solar panels of Percy.

    Percy did "see" that dust was on Ingenuity's solar panels before its first flight, and expected it to come off. The Solar Panels are above the propellers:
    https://www.youtube.com/watch?v=RXPU_Mjf69M

    I imagine that you don't want Ingenuity to fly too close to Percy, or at least to be programmed to have measured distance so it doesn't accidentally fall into Percy. That would be cataclysmic.

    Larry
    DevilHorse

  11. #331
    Quote Originally Posted by CameronBornAndBred View Post
    When Percy's solar panels get dusty, they should have Ingenuity land on each one.
    If you didn't get your fill of pictures from Mars, check this page of Raw Images out:
    https://mars.nasa.gov/mars2020/multimedia/raw-images/
    You can (quickly) go through the varied pictures taken by Percy as it 'tools' around its basin on Mars. You can even catch a dust devil in the background in one shot (Raw Image Of The Week).

    Interestingly, there are many shots taken of Percy itself, and you'll notice that after a couple of months there is relatively little dust on Percy, even though the ground seems to be loose dust. You'd expect a bit of it to kick up, or blow up onto Percy. but apparently it isn't sticking (fortunately). <makes this comment apropos to your suggestion>.

    Larry
    DevilHorse

  12. #332

    Pluto from New Horizons (2015)

    My friends, I give you Pluto..

    https://twitter.com/i/status/1409634434995802113

    Courtesy of New Horizons (2015). Pluto Rocks!

    Larry
    DevilHorse

  13. #333
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    Quote Originally Posted by DevilHorse View Post
    My friends, I give you Pluto..

    https://twitter.com/i/status/1409634434995802113

    Courtesy of New Horizons (2015). Pluto Rocks!

    Larry
    DevilHorse
    That's awesome. And speaking of things that are way out there, I'm enjoying the recent news about this "comet". Although it's not certain if it is really a comet, or some tiny minor planet. And it's not certain how big it actually is. Somewhere between 60 and 230 miles wide, with an orbit that spans anywhere from 600,000 to 5 million years. We'll know more of course as it gets closer, the closest being alongside the orbit of Saturn in 2031.

    https://newatlas.com/space/2014-un27...em-close-pass/

    https://en.wikipedia.org/wiki/C/2014...lli-Bernstein)
    Q "Why do you like Duke, you didn't even go there." A "Because my art school didn't have a basketball team."

  14. #334
    Quote Originally Posted by CameronBornAndBred View Post
    That's awesome. And speaking of things that are way out there, I'm enjoying the recent news about this "comet". Although it's not certain if it is really a comet, or some tiny minor planet. And it's not certain how big it actually is. Somewhere between 60 and 230 miles wide, with an orbit that spans anywhere from 600,000 to 5 million years. We'll know more of course as it gets closer, the closest being alongside the orbit of Saturn in 2031.

    https://newatlas.com/space/2014-un27...em-close-pass/

    https://en.wikipedia.org/wiki/C/2014...lli-Bernstein)
    That's an interesting object indeed. Needs a catchier name to be picked up by the news services I'd think. But will not be very bright (no brighter than Pluto's moon) and is a decade away from being at its closest approach. I imagine we have a lot of these slow moving visitors that we just never noticed before that have orbits askew of the ecliptic. With a perihelion at Saturn and brightness less than Pluto, this will be the limpest comet I've ever heard of. Or should I say highest ratio of excitement to brightness.

    I note that the articles cited use imprecise language. i) Not visiting the "Inner Solar System"; it would have to reach Mars, or perhaps the Asteroid Belt to do that. And it will only perhaps be outside of Saturn. ii) uses 'minor planet' instead of 'dwarf planet' designation. These things throw me off when trying to read about it.

    Thanks for bringing this up. Let's hope WE are all around to welcome this, and other strange visitors, from a distance, in 10 years.

    Larry
    DevilHorse

  15. #335
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    Quote Originally Posted by DevilHorse View Post
    I note that the articles cited use imprecise language. i) Not visiting the "Inner Solar System"; it would have to reach Mars, or perhaps the Asteroid Belt to do that. And it will only perhaps be outside of Saturn. ii) uses 'minor planet' instead of 'dwarf planet' designation. These things throw me off when trying to read about it.
    This was my favorite. It's not a comet, nor a mini planet. And it's no moon. It's a Death Star!

    https://www.slashgear.com/2014-un271...stem-23679599/
    Q "Why do you like Duke, you didn't even go there." A "Because my art school didn't have a basketball team."

  16. #336
    Quote Originally Posted by CameronBornAndBred View Post
    This was my favorite. It's not a comet, nor a mini planet. And it's no moon. It's a Death Star!

    https://www.slashgear.com/2014-un271...stem-23679599/
    It is a fun object. It is about 1/6 the diameter of the smallest classified Dwarf Planet, and we really don't know its shape, so calling it a Dwarf Planet is premature.

    Ever notice how the Death Star never recoiled? Either it had some (never mentioned) gravitational brake holding it in place, or it defied the known laws of physics when it blasted any planet. It should have plastered its inhabitants against all of the windows and control rooms every time. Energy has momentum too, assuming that you are destroying a planet. But then, that is Star Wars and Death Stars always seemed to lose and not get reused (the Emperor's little secret).

    Larry
    DevilHorse

  17. #337
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    Quote Originally Posted by DevilHorse View Post
    Ever notice how the Death Star never recoiled? Either it had some (never mentioned) gravitational brake holding it in place, or it defied the known laws of physics when it blasted any planet. It should have plastered its inhabitants against all of the windows and control rooms every time. Energy has momentum too, assuming that you are destroying a planet. But then, that is Star Wars and Death Stars always seemed to lose and not get reused (the Emperor's little secret).
    The damn thing could fly through hyperspace. Never question Star Wars, you'll hurt your brain.
    Q "Why do you like Duke, you didn't even go there." A "Because my art school didn't have a basketball team."

  18. #338
    Quote Originally Posted by CameronBornAndBred View Post
    The damn thing could fly through hyperspace. Never question Star Wars, you'll hurt your brain.
    It could fly?! So they claim. But there was never any "film" of a propulsion system. And the one view of the center of the Death Star showed no apparent gyroscopes. That thing should be spinning in space and whipping people to the outside of the craft. I know it is a detail, but... really. When thinking of UFOs and spacecraft, Globes are not great spacecrafts IMHO. Super efficient for keeping heat inside though. But very scary.

    And how is it that what the Emperor wants to see is always outside the window of his office/throne? How convenient?! Is this a movie or something? Well yes..

    Larry
    DevilHorse

  19. #339

    Orbiters

    Ran across this interesting tally:
    orbiters1.gif
    List (I expect) includes rovers on Mars, but doesn't include craft that pass through the solar system like New Horizon, Voyager, and those craft that land on comets to retrieve rocks like Philae. Mars is definitely getting a big share of the attention; much more than the moon (been there, done thatism?).

    Found this (perhaps slightly outdated) chart of all the Rovers on planets/moons:
    rovers1.jpg

    In other news, LIGO getting more signals of a Black Hole swallowing a Neutron Star. More confirmation of Gravitational Waves, suggestive of gravitons.
    Larry
    DevilHorse

  20. #340
    Quote Originally Posted by CameronBornAndBred View Post
    When Percy's solar panels get dusty, they should have Ingenuity land on each one.
    Here is a timely post about dust on another rover's solar panels that (at least) suggests that NASA would be on top of thinking about this problem:
    https://twitter.com/latestinspace/st...816141/photo/1

    Larry
    DevilHorse

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