If you want to understand about the sun's history, go no farther than the moon. That's the advice of a group of scientists who plan to use future Artemis lunar missions to learn more about our star's life cycle. The sun has always had an impact on all of the bodies in the solar system. We receive not just heat and light from the sun, but also a steady downpour of high-energy particles and solar wind. And this has been happening every day for the previous 4.5 billion years, not just today.
However, on worlds such as Earth, we have forgotten the old history of the sun's effect on humans. Wind weathering, water erosion, and the repeated cycles of plate tectonics remove any adjustments caused by the sun on our crust and either blow it away or bury it deep beneath our mantle. According to a new white paper published in the preprint magazine arXiv, dead planets are considerably better record keepers. And, because the moon is the closest dead world to us and the goal of the Artemis series of missions, we should travel there to look.
Since the moon's creation, there has been some surface activity, including as lava flows and asteroids and comet impacts. However, according to the white paper, such exercise is really beneficial rather than detrimental. Large parts of the moon's surface can be sealed off from further interaction with the sun by lava flows. We would have a snapshot of solar history from before the lava flowed if we could dig underneath the flows and into the deeper regolith of the moon.
While hits tend to jumble things up, they also expose deeper levels of the surface, allowing us easy access to them. The researchers described a few critical parameters that may be measured from lunar samples and how they relate to solar activity. For example, we may use the length of time a sample has been exposed to cosmic rays to calculate the rate of cosmic ray production from the sun over the last several billion years.
To gain the same information, we may look at the tracks made by high-energy particles as they dig through the crust. The quantity of solar radiation alters the rate at which lunar soil converts into brecchia. We can comprehend the variation in the brightness of the sun over time by comparing multiple samples at different depths and places. There is no more accessible spot in the solar system to peek into the sun's past history, according to the white paper. To put it simply, the moon is a solar time capsule.
Journal Information: Prabal Saxena, Natalie Curran, Heather Graham, Lunar Samples are Time Capsules of the Sun. arXiv:2208.13307v2 [astro-ph.IM], arxiv.org/abs/2208.13307