Surrounding Earth is a powerful magnetic field created by swirling liquid iron in the planets core.
But did the Moons core generate a magnetic field in the past?
But a robust magnetic field requires a power source, and the Moons core is relatively small.
Im aprofessor of geophysicsand have beenstudying Earths magnetic field for more than 30 years.
I recently assembled a team to use new scientific techniques to reexamine the evidence for lunar magnetization.
We found thatthe Moon did not in fact have a long-lived magnetic field.
Image via Rory Cottrell/U.
Rochester, CC BY-ND
Why a magnetic Moon?
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This allows researchers tolearn about past magnetic fields.
But they faced problems.
Lunar rocks contain a certain bang out of iron called native iron thatis easily altered by heat.
From the 1970s onward, geophysicists used alternative, nonheating methods to study the Moons magnetism.
But this result only deepened the conundrum.
The question of how the Moons core could produce a strong magnetic fieldremained unsolved.
The white scale bar is 1 mm.
Some researchers attributed the missing magnetization to the presence of large native iron grains that were poor magnetic recorders.
But many of the samples also contained small iron grains that should have recorded a field.
There have beenlong-standing doubts about the nonheating techniquesresearchers used on the Apollo samples.
In 2008, geophysicistKristin Lawrencedecided to revisit the question of lunar magnetization using an improved reheating technique.
Image via Adam Fenster/U.
Rochester, CC BY-ND
In 2011, Lawrence brought us a collection of lunar samples to test.
We found that nearly all the rocks had profoundly weak magnetic signals.
But we have been improving our testing methods, and last year we decided to revisit the Apollo samples.
But the rocks had recorded no such signals.
This suggests that the Moon lacked a magnetic field for nearly all of its history.
So, what explains the previous findings of a magnetic Moon?
Image via Rory Cottrell/U.
But it was formed only about 2 million years ago.
The magnetic signature of the glass matched simulations of magnetic fields that can begenerated by meteor impacts.
This showed that meteorite impacts alone can create strong magnetic fields that magnetize rocks nearby.
This could explain the high values previously reported from some Apollo rocks.
Taken together, I believe these findings deal with the mystery of a seemingly magnetic Moon.
Image via Michael Osadciw/U.
Magnetic fields act as shields thatprevent solar particles from reaching a planet or moon.
There is also scientific value.
Elements embedded by solar wind could shed light on the evolution of the Sun.
