Summary: The powdery “dirt” that covers much of the lunar surface is almost as dark as charcoal. In the far-distant past, though, it was almost white. It’s been darkened by exposure to radiation — mainly the flow of charged particles from the Sun known as the solar wind. Yet the lighter color still shows through in some beautiful patterns known as lunar swirls. They look like dollops of cream being swirled into a cup of coffee. A recent study says the swirls are protected by magnetic “bubbles” that deflect the solar wind. The Moon doesn’t generate a magnetic field today, but it did in the distant past. That magnetized the rocks, which create their own magnetic fields around them. The study found that in places, these fields produce magnetic bubbles that extend dozens of miles above the surface. They deflect the negatively charged particles known as electrons around the bubble. The electrons hit the lunar surface at the edges of the bubble, forming a dark outline. Funneling away the electrons creates an electric field that shoots the positively charged protons in the solar wind back into space. The result is a lunar deflector shield — a magnetic bubble that blocks radiation, keeping the surface below nice and bright. Look for the Moon in the east at first light tomorrow. The bright star Regulus, the “heart” of Leo, the lion, is to its left or lower left. And Venus, the “morning star,” is well below them. More about Venus and the Moon tomorrow. Script by Damond Benningfield, Copyright 2012 For more skywatching tips, astronomy news, and much more, read StarDate magazine.
