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View Diary: Back When the Earth Had Two Moons (67 comments)

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  •  Our Moon also has "lumpy" gravity (6+ / 0-)

    Quotes from a NASA website:

    "The Moon is extraordinarily lumpy, gravitationally speaking," Konopliv continues. "I don't mean mountains or physical topography. I mean in mass. What appear to be flat seas of lunar lava have huge positive gravitational anomalies—that is, their mass and thus their gravitational fields are significantly stronger than the rest of the lunar crust." Known as mass concentrations or "mascons," there are five big ones on the front side of the Moon facing Earth, all in lunar maria (Latin for "seas") and visible in binoculars from Earth.

    The mascons' gravitational anomaly is so great—half a percent—that it actually would be measurable to astronauts on the lunar surface. "If you were standing at the edge of one of the maria, a plumb bob would hang about a third of a degree off vertical, pointing toward the mascon," Konopliv says. Moreover, an astronaut in full spacesuit and life-support gear whose lunar weight was exactly 50 pounds at the edge of the mascon would weigh 50 pounds and 4 ounces when standing in the mascon's center.

    This makes it difficult to keep satellites in a stable lunar orbit:

    "Lunar mascons make most low lunar orbits unstable," says Konopliv. As a satellite passes 50 or 60 miles overhead, the mascons pull it forward, back, left, right, or down, the exact direction and magnitude of the tugging depends on the satellite's trajectory. Absent any periodic boosts from onboard rockets to correct the orbit, most satellites released into low lunar orbits (under about 60 miles or 100 km) will eventually crash into the Moon. PFS-2 released by Apollo 16 was simply a dramatic worst-case example. But even its longer-lived predecessor PFS-1 (released by Apollo 15) literally bit the dust in January 1973 after less than a year and a half.

    http://science.nasa.gov/...

    = = = = =

    And this causes the Earth Moon Lagrange points (EML1 & EML2) to be ideal locations for a lunar orbiting equivalent of the International Space Station.

    •  Wonder if that's from iron-rich (0+ / 0-)

      meteor strikes?  The creation of the maria would require something dense ....

      --

      Republicans chap my ass

      Me

      by Marc in KS on Thu Aug 04, 2011 at 02:50:27 PM PDT

      [ Parent ]

      •  Or not enough heat during formation to melt (0+ / 0-)

        the core completely before cooling.....

        FDR 9-23-33, "If we cannot do this one way, we will do it another way. But do it we will.

        by Roger Fox on Thu Aug 04, 2011 at 03:51:17 PM PDT

        [ Parent ]

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