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Walk, Don’t Run, on Martian Moon Phobos

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

"exec" writes:

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.

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Original Submission

• Reminded me of this blast from the past... (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.

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