Was the Sun a Slow Rotator? Sodium and Potassium Constraints from the Lunar Regolith

While the Earth and Moon are generally similar in composition, a notable difference between the two is the apparent depletion in moderately volatile elements in lunar samples. This is often attributed to the formation process of the Moon, and it demonstrates the importance of these elements as evolu...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2019-05, Vol.876 (1), p.L16
Main Authors: Saxena, Prabal, Killen, Rosemary M., Airapetian, Vladimir, Petro, Noah E., Curran, Natalie M., Mandell, Avi M.
Format: Article
Language:English
Subjects:
Analogs
Bombardment
Depletion
Earth-Moon system
Habitability
Impactors
Lunar crust
Lunar evolution
Lunar regolith
Lunar surface
Moon
Planetary evolution
Planetary surfaces
planets and satellites: surfaces
planets and satellites: terrestrial planets
Potassium
Regolith
Sodium
Solar activity
Solar Physics
Solar system
Solar system evolution
Space weather
Sun
Sun: coronal mass ejections (CMEs)
Sun: evolution
Sun: rotation
Tracers
Volatile compounds
Weather
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Summary:While the Earth and Moon are generally similar in composition, a notable difference between the two is the apparent depletion in moderately volatile elements in lunar samples. This is often attributed to the formation process of the Moon, and it demonstrates the importance of these elements as evolutionary tracers. Here we show that paleo space weather may have driven the loss of a significant portion of moderate volatiles, such as sodium and potassium, from the surface of the Moon. The remaining sodium and potassium in the regolith is dependent on the primordial rotation state of the Sun. Notably, given the joint constraints shown in the observed degree of depletion of sodium and potassium in lunar samples and the evolution of activity of solar analogs over time, the Sun is highly likely to have been a slow rotator. Because the young Sun's activity was important in affecting the evolution of planetary surfaces, atmospheres, and habitability in the early Solar System, this is an important constraint on the solar activity environment at that time. Finally, as solar activity was strongest in the first billion years of the Solar System, when the Moon was most heavily bombarded by impactors, evolution of the Sun's activity may also be recorded in lunar crust and would be an important well-preserved and relatively accessible record of past Solar System processes.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/ab18fb