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posted by Fnord666 on Saturday August 12 2017, @10:27AM   Printer-friendly
from the pulling-for-the-moon dept.

The Moon's magnetic field was much stronger than it is today for longer than previously thought (alt link):

New evidence from ancient lunar rocks suggests that an active dynamo once churned within the molten metallic core of the moon, generating a magnetic field that lasted at least 1 billion years longer than previously thought. Dynamos are natural generators of magnetic fields around terrestrial bodies, and are powered by the churning of conducting fluids within many stars and planets.

In a paper published today in Science Advances, researchers from MIT and Rutgers University report that a lunar rock collected by NASA's Apollo 15 mission exhibits signs that it formed 1 to 2.5 billion years ago in the presence of a relatively weak magnetic field of about 5 microtesla. That's around 10 times weaker than Earth's current magnetic field but still 1,000 times larger than fields in interplanetary space today.

Several years ago, the same researchers identified 4-billion-year-old lunar rocks that formed under a much stronger field of about 100 microtesla, and they determined that the strength of this field dropped off precipitously around 3 billion years ago. At the time, the researchers were unsure whether the moon's dynamo — the related magnetic field — died out shortly thereafter or lingered in a weakened state before dissipating completely.

The results reported today support the latter scenario: After the moon's magnetic field dwindled, it nonetheless persisted for at least another billion years, existing for a total of at least 2 billion years.

A two-billion-year history for the lunar dynamo (open, DOI: 10.1126/sciadv.1700207) (DX)

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  • (Score: 3, Informative) by requerdanos on Saturday August 12 2017, @10:59PM (3 children)

    by requerdanos (5997) Subscriber Badge on Saturday August 12 2017, @10:59PM (#553016) Journal

    Dynamos are natural generators of magnetic fields around terrestrial bodies

    And presumably also around selenial [] bodies, then?

    • (Score: 2) by coolgopher on Sunday August 13 2017, @03:55AM (2 children)

      by coolgopher (1157) Subscriber Badge on Sunday August 13 2017, @03:55AM (#553096)

      Careful, we might end up arguing the IAU definition of "planet" if we're not careful! :)

      • (Score: 0) by Anonymous Coward on Sunday August 13 2017, @06:55PM (1 child)

        by Anonymous Coward on Sunday August 13 2017, @06:55PM (#553326)
        • (Score: 3, Interesting) by takyon on Sunday August 13 2017, @07:40PM

          by takyon (881) Subscriber Badge <reversethis-{gro ... s} {ta} {noykat}> on Sunday August 13 2017, @07:40PM (#553341) Journal

          There is the possibility of a Mars-sized object at the edge of the Kuiper belt []:

          According to the calculations, an object with the mass of Mars orbiting roughly 60 AU from the sun on an orbit tilted by about eight degrees (to the average plane of the known planets) has sufficient gravitational influence to warp the orbital plane of the distant KBOs within about 10 AU to either side.

          The known KBO population is about to expand greatly []:

          Though no planet-size objects have been spotted in the Kuiper Belt so far, the researchers are optimistic that the Large Synoptic Survey Telescope (LSST), which is currently under construction in Chile, will help find these hidden worlds. "We expect LSST to bring the number of observed KBOs from currently about 2,000 to 40,000," Malhotra said.

          Many of those objects will be much smaller than Pluto, but some of the more distant ones with darker albedos may be larger.

          [SIG] 10/28/2017: Soylent Upgrade v14 []