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Moon China Space

China's Rover Reveals Moon's Hidden Depths (scientificamerican.com) 48

Posted by BeauHD from the structure-of-the-moon dept.
China's Chang'e-4 mission to the dark side of the moon has discovered signs of mantle material at the moon's surface, "effectively setting an 'X' on lunar maps for future explorers seeking this not-so-buried geological treasure," reports Scientific American. From the report: China's Chang'e-4 mission touched down near the south pole on the lunar far side on January 3, 2019, the first spacecraft ever to land intact on this largely unexplored region of the moon. Consisting of a lander and rover, the mission is still going strong today, with the rover -- called Yutu-2 -- continuing its journey across the surface. On board are a variety of instruments, and today in Nature scientists from the Chinese Academy of Sciences in Beijing report the mission's first scientific results, suggesting lunar mantle material has at last been located.

"We found that the material of the Chang'e-4 landing site is mainly composed of olivine and low-calcium pyroxene," says Dawei Liu, one of the paper's co-authors. "This mineral combination is the candidate mantle-derived material." Chang'e-4 rests inside the South Pole-Aitken (SPA) basin, which, at 2,500 kilometers across, is one of the solar system's oldest and largest known impact craters. Specifically, the mission touched down in the 186-kilometer-wide Von Karman crater within this larger basin. Von Karman was produced billions of years ago by the impact of a large comet or asteroid; such collisions can excavate mantle material from deep underground, allowing it to be scattered across the surface by subsequent impacts.

The mantle material was discovered using the Visible and Near Infrared Spectrometer on Yutu-2, which can ascertain the chemical composition of rocks by studying their reflected light. Both olivine and pyroxene are believed to be among the first minerals that froze out from the moon's magma ocean as it cooled, falling to its solid base deeper in the mantle. Because previous surveys from orbit have revealed much of Von Karman's floor to be composed of lava from volcanic eruptions rather than excavated mantle, the paper's authors suspect the material detected by Yutu-2 was actually blasted into Von Karman from the upper mantle beneath another nearby impact structure, the 72-kilometer-wide Finsen crater.
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China's Rover Reveals Moon's Hidden Depths

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  • "Dark side"? (Score:4)

    by Darren Hiebert ( 626456 ) on Friday May 17, 2019 @06:17AM (#58607282) Homepage
    I hope everyone realizes that the Moon has no "dark side", per se. The Moon rotates on its axis once per month, synchronized with its orbit around the Earth, such that the same side always faces Earth because its rotation is tidally locked with the Earth. It should be obvious that during the new moon (where we don't see the Moon, or it's barely a sliver of a crescent), the back side of the Moon is facing, and lit by, the Sun. The term "dark side" of the Moon is sometimes used (and really should be places in quotes) to describe the side that always faces away from us and that we never see it lit, and so it remains "dark" to our knowledge.

    • Re: (Score:1)

      by Anonymous Coward

      Yeah, it's an idiosyncrasy of English. Other languages use more proper terms, in French it's "face cachée" (hidden side) and in Spanish it's "cara oculta" (occult side).

      • Re:"Dark side"? (Score:4, Informative)

        by Zocalo ( 252965 ) on Friday May 17, 2019 @07:58AM (#58607628) Homepage
        "Dark" actually would be a proper term in English, it's just that the usage to mean an absence of knowledge (or conversely being "illuminated" upon its acquisition) isn't so common in modern English, so people just assume it can only mean an absence of light or something to do with being evil. For instance, the term "Dark Ages" actually refers to a lack of much in the way of reliably recorded history about the period being available, not a lack of progress as is commonly assumed - quite incorrectly as it turns out, since there was a fair bit of scientific and engineering progress before the Renaissance.
        • But I thought it was called the Dark Ages because there were so many knights...

        • For instance, the term "Dark Ages" actually refers to a lack of much in the way of reliably recorded history about the period being available, not a lack of progress as is commonly assumed - quite incorrectly as it turns out, since there was a fair bit of scientific and engineering progress before the Renaissance.
          Correct. Funnily even the wikipedia article is wrong (used to be? to lazy to check it now) wrong about that.

    • Re:"Dark side"? (Score:5, Funny)

      by dddux ( 3656447 ) on Friday May 17, 2019 @07:39AM (#58607536)
      Blame it on the Pink Floyd, mate. :)

      • Re: (Score:1)

        by Anonymous Coward

        Matter of fact, it's all dark.

    • Put this one in the same box where we store the knowledge that "the days are getting longer."

      Days, by definition are approx. 24 hours.

      Daylight is another matter.

  • Given the same side of the moon always faces the earth, the "far side" of the moon is always opposite of the earth.....meaning when on the surface of the far side, the moon is between the rover and earth.

    If I am correct in understanding positions of the rover to earth, how does it communicate back to earth? Do the Chinese have their own satellites to assist?

    I'd love to know more....

    • Good question and here's more.

      You are absolutely correct that the equipment on the other side of the Moon is pretty much shielded from Earthly contamination, and also, cannot send signals back to Earth in that same direction.

      An alternate route exists. Like me, you'll kick yourself for not thinking of this:

      There's another craft in orbit up there, and off to the side that's constantly line-of-sight with both the far side of the Moon and the Earth.

    • Well, not exactly at L2, but orbiting in a circle around it. L2 is a Lagrangian point - a gravitationally stable point between the Earth and Moon. Several of these points exist, and L2 is behind the Moon (as viewed from the Earth). If they parked the relay satellite [wikipedia.org] at L2, the Moon would block it from view from the Earth. So they put it into a halo orbit [wikipedia.org], meaning it circles L2, just far enough away from L2 that it peeks around the edge of the Moon and we can always see it from Earth, but it also has a v

    • They have a satellite in a so called "halo orbit" around earth/moon Lagrange point 2. That means from the point of view of the earth the satellite is in a kind of ring orbit (like finger ring) around that point behind the moon. Like the halo of a full moon, that satellite is always visible from earth, its orbit plane is perpendicular to the direct line of sight.

      https://www.space.com/30302-la... [space.com]
      https://en.wikipedia.org/wiki/... [wikipedia.org]

  • “There is no dark side of the moon really. As a matter of fact it's all dark.” -- Pink Floyd

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