The Moon is bombarded by so much space rock that its surface gets a complete facelift every 81,000 years, according to a study released Wednesday based on NASA data.
By comparing images of the same area at regular intervals, a team of scientists led by Emerson Speyerer from Arizona State University in Tempe were able to tally the number of new craters and extrapolate to the entire surface of the Moon.
"We detected 222 new impact craters and found 33 percent more craters with a diameter of at least 10 metres than predicted" by earlier models, the researchers concluded.
The scientists also found thousands of subtler disturbances on the surface, which they described as "scars" from smaller, secondary impacts that –- over thousands of years –- churned up the top layer of the Moon without creating craters.
One of the key science findings is that the emission and re-absorption of photo/secondary electrons at the walls of micro-cavities formed between neighboring dust particles can generate unexpectedly large electrical charges and intense particle-particle repulsive forces. This can cause dust particles to move and lift off the surface, or "levitate." And not just single-sized dust particles—large aggregates can be lofted as well.
We expect dust particles to mobilize and transport electrostatically over the entire lunar surface, as well as the surface of any other airless planetary body," Wang said. "If so, electrostatic dust activity may be also responsible for the degradation of retroreflectors on the lunar surface."
The laboratory observations also showed dusty surfaces becoming smooth as a consequence of dust mobilization. These electrostatic dust processes could help to explain the formation of the "dust ponds" on asteroid Eros and comet 67P, and the unexpectedly smooth surface on Saturn's icy satellite Atlas.
What's more, this electrostatic dust mobilization may help explain the formation of "dust ponds" on asteroid Eros and Comet 67P/Churyumov-Gerasimenko, as well as the smooth surface on Saturn's icy moon Atlas"
""This new 'patched charge model' resolved a fundamental mechanism of dust charging and transport, which has been puzzling scientists for decades," Xu Wang"
"Powerful solar storms can charge up the soil in frigid, permanently shadowed regions near the lunar poles, and may possibly produce "sparks" that could vaporize and melt the soil, perhaps as much as meteoroid impacts"
"on the moon, these particles—ions and electrons—slam directly into the surface. They accumulate in two layers beneath the surface; the bulky ions can't penetrate deeply because they are more likely to hit atoms in the regolith, so they form a layer closer to the surface while the tiny electrons slip through and form a deeper layer. The ions have positive charge while the electrons carry negative charge"
-comment: ie an electric discharge"In August 2014, however, Jordan's team published simulation results predicting that strong solar storms would cause the regolith in the moon's permanently shadowed regions (PSRs) to accumulate charge in these two layers until explosively released, like a miniature lightning strike."
-comment, the rules for distinguishing are already well established (thunderbolts video https://www.youtube.com/watch?v=5ThZZPCMXNU), very good that NASA is studying this."Laboratory on experiments to see how breakdown affects the regolith and to look for any tell-tale signatures that could distinguish it from the effects of meteoroid impacts."
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