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posted by mrpg on Sunday November 18 2018, @07:32AM   Printer-friendly
from the scary dept.

Arthur T Knackerbracket has found the following story:

Walk, don’t run, on the martian moon Phobos. A new study finds that traveling faster than about 5 kilometers per hour on some regions of the Red Planet’s largest satellite could shoot you straight off into space.

Phobos (pictured[*]) is an odd duck among our solar system’s moons. It’s tiny (a fraction of a percent the size of our own moon) and is shaped like a potato; that weird shape draws gravity to different places, depending on where you are.

All these features make Phobos a challenge to travel on, researchers report in Advances in Space Research. In some places, moving any faster than 5 kilometers per hour would be enough to free you from the moon’s meager gravitational pull, sending you off into space where you’d likely be captured by Mars’s gravity and end up orbiting the Red Planet. The fastest you could travel anywhere on Phobos would be about 36 kilometers per hour, or a little faster than a golf cart, the team finds.

[*] Here is a link to the picture.

-- submitted from IRC


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  • (Score: 2) by MostCynical on Sunday November 18 2018, @10:12AM (2 children)

    by MostCynical (2589) on Sunday November 18 2018, @10:12AM (#763425) Journal

    Good thing you'd be wearing a full space suit, or you could sneeze yourself into orbit.

    --
    "I guess once you start doubting, there's no end to it." -Batou, Ghost in the Shell: Stand Alone Complex
    • (Score: 3, Funny) by isostatic on Sunday November 18 2018, @11:48AM (1 child)

      by isostatic (365) on Sunday November 18 2018, @11:48AM (#763442) Journal

      A typical sneeze will come out at 5m/s and top out at 20g, which means even a lightweight 50kg person would accelerate about 2mm/second, or 5-10 metres per hour, several orders of magnitude less than required to reach escape veolicty.

      • (Score: 2, Funny) by Anonymous Coward on Sunday November 18 2018, @04:08PM

        by Anonymous Coward on Sunday November 18 2018, @04:08PM (#763514)

        I would be more concerned about the strongest possible sneeze than a typical one, since a single huge sneeze could cause problems.

  • (Score: 3, Funny) by Nuke on Sunday November 18 2018, @10:21AM (2 children)

    by Nuke (3162) on Sunday November 18 2018, @10:21AM (#763426)

    This can't be true. The game of Doom was set on Phobos, and I didn't go into orbit when I ran.

    • (Score: 2) by Unixnut on Sunday November 18 2018, @11:06AM (1 child)

      by Unixnut (5779) on Sunday November 18 2018, @11:06AM (#763432)

      Your BFG weapon (plus the armour and power assistance to wield it) meant you had a lot more mass on Phobos than these "peaceful" explorers with their flimsy light suits have.

      Hence you didn't have to worry about launching yourself into orbit (as easily).

      • (Score: 4, Informative) by isostatic on Sunday November 18 2018, @11:42AM

        by isostatic (365) on Sunday November 18 2018, @11:42AM (#763440) Journal

        Doesn't matter if you weigh 20 grammes or 20 tons, if you're traveling at 5kph, you're going into orbit. Sure the extra mass will make it harder to accelerate to 5kph, but in Doom you could run even with that equipment. And carry a dozen weapons.

        However the base in Doom had artificial gravity so it's a moot point.

  • (Score: 2) by inertnet on Sunday November 18 2018, @11:09AM (3 children)

    by inertnet (4071) on Sunday November 18 2018, @11:09AM (#763433) Journal

    I don't think you could generate enough friction to reach those speeds there, just by walking or running.

    • (Score: 2) by takyon on Sunday November 18 2018, @11:29AM (2 children)

      by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Sunday November 18 2018, @11:29AM (#763438) Journal

      Yeah, the only way we will be running around there is if we hollow it out, spin it, and turn it into a space station.

      --
      [SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
      • (Score: 2) by Immerman on Sunday November 18 2018, @02:59PM (1 child)

        by Immerman (3985) on Sunday November 18 2018, @02:59PM (#763497)

        At a mean diameter of 22 km, with a mass of 10^16 kg, spinning it up would be a major project, and would likely tear the thing apart anyway. However, if you were to excavate a large round chamber you could put a "traditional" rotating torus space station underground, while only needing minimal stabilization. Build it near the center of the moon, and you'll even be in freefall, which would simplify a few things.

        Doesn't have the easy expansion potential of tunneling into a spinning moon - but unless the thing is solid rock with high tensile strength, that "gravity" that holds your feet to the floor is going to be hurling the surface into space as well. And building a bag strong enough to hold all the bits of a spinning asteroid together could be a real challenge.

        • (Score: 2) by takyon on Sunday November 18 2018, @03:31PM

          by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Sunday November 18 2018, @03:31PM (#763509) Journal

          Perhaps some strategic excavation, melting, construction, etc. could be used to strengthen Phobos and Deimos and make them sturdier than mere "rubble piles".

          Alternatively we could hasten the process of ripping it into smaller, more manageable chunks.

          Or we could redirect smaller asteroids into orbit around Earth/Moon, Mars, or Ceres and try it on those.

          --
          [SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
  • (Score: 2) by suburbanitemediocrity on Sunday November 18 2018, @03:43PM (1 child)

    by suburbanitemediocrity (6844) on Sunday November 18 2018, @03:43PM (#763511)
    • (Score: 2) by bob_super on Sunday November 18 2018, @06:59PM

      by bob_super (1357) on Sunday November 18 2018, @06:59PM (#763579)

      Yep. "Asteroids have so little gravity you can jump/run to orbit" isn't news. That's pretty much why there are sample return missions in space right now.

  • (Score: 0) by Anonymous Coward on Sunday November 18 2018, @11:48PM (1 child)

    by Anonymous Coward on Sunday November 18 2018, @11:48PM (#763666)

    https://www.webtender.com/cgi-bin/search?name=&ingr=creme+de+menth&what=drink&show=50&verbose=on [webtender.com]

    Drink search results
        Search for drinks with ingredient(s) 'creme de menth'. Hits 1 - 50 of 973.
            Show hits 51 - 100 | Hide details

    1. Emerald Forest (Ordinary Drink. Alcoholic.)
    Ingredients: Ice, Gin, Green Creme de Menthe, White Creme de Menthe
    2. Astroturf (Ordinary Drink. Alcoholic.)
    Ingredients: Green Creme de Menthe, Creme de Cacao, Milk, Chocolate syrup
    ...

    • (Score: 2) by Fluffeh on Monday November 19 2018, @09:08PM

      by Fluffeh (954) Subscriber Badge on Monday November 19 2018, @09:08PM (#764016) Journal

      Nice one...

      Now, people looking for drink recipes with creme de menthe will end up in this discussion about the escape velocity of a martian moon...

      Did you consider that before posting to the wrong article? Well, did you? The shame you bring to your family must keep them awake at night grinding their teeth!

  • (Score: 2) by All Your Lawn Are Belong To Us on Monday November 19 2018, @06:00AM

    by All Your Lawn Are Belong To Us (6553) on Monday November 19 2018, @06:00AM (#763804) Journal

    They were down on Phobos.
    Pollux got up from where he had sprawled on the deck-plates – and bumped his head on the overhead. After that he tried to walk like Jason Thomas. He had weight, real weight, for the first time since Luna, but it amounted to only two ounces in his clothes. "I wonder how high I can jump here?" he said.
    "Don't try it," Hazel advised. "Remember the escape velocity of this piece of real estate is only sixty-six feet a second."
    "I don't think a man could jump that fast"
    "There was Ole Gunderson. He dived right around Phobos – a free circular orbit thirty-five miles long. Took him eighty-five minutes. He'd have been traveling yet. If they hadn't grabbed as he came back around."
    "Yes, but wasn't he an Olympic jumper or something? And didn't he have to have a special rack or some such to take off from?"
    "You wouldn't have to jump," Castor put in. "Sixty-six feet a second is forty-five miles an hour, so the circular speed comes out a bit more than thirty miles an hour. A man can run twenty miles an hour back home, easy. He could certainly get up to forty-five here."
    Pollux shook his head. "No traction."
    "Special spiked shoes and maybe a tangent launching ramp for the last hundred yards – then woosh! off the end and you're gone for good."
    "Okay, you try it, Grandpa. I'll wave good-by to you."

    Robert A. Heinlein, The Rolling Stones, 1952 And escape velocity (apparently without the libration effects that TFA's reference discusses) is actually about 25 mph if Google knows what it is talking about. ;) That would be some heavy libration to bring it down to 3 mph I think. Wish I were better at planetary dynamics to digest and check it for myself.

    --
    This sig for rent.
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