For centuries, the surface of the Moon has harbored a mystery: bright, sinuous spirals that cover thousands of square kilometers of the lunar surface, visible but unexplained by telescopes on Earth. Now, scientists are finally beginning to unravel the mystery, and it turns out to be stranger than anyone could have imagined. These enigmatic “Moon spirals” are the result of an ancient underground force field that protects the Moon from a barrage of subatomic particles blasting from the Sun. Each spiral is a twisted blanket of pure rock, tangled with irradiated, blackened material.
While most of the Moon’s surface features are jagged and rugged, the Moon’s spirals are smooth and faint, like cirrus clouds painted on the surface. The spirals are widespread, with some appearing in Mare Marginis (Latin for “edge sea” because it is the eastern edge of the Moon’s surface as seen from Earth) and others in Reiner Gamma, thousands of kilometers to the west. The spirals are found both in the smooth, dark lowlands of maria (Latin for “ocean”; vaguely resembling a sea when seen with the naked eye from Earth) and in the heavily cratered highlands, suggesting that they are not associated with any particular feature. The spirals are brighter than the maria (plains of dark, flooded basaltic lava), making it easier to spot the Moon’s spirals in those areas.
Observers have long noticed that the spirals aren’t landforms like hills or valleys because they don’t cast shadows, but instead resemble the formations created when clouds collapse onto the ground. That wouldn’t be possible on the Moon without an atmosphere.And even if such “cloud collapse” could occur there, recent observations of the moon’s spirals indicate that they are made of the same material as their surroundings. do not have It is not a covered substance, but rather part of the existing surface.
Supporting science journalism
If you enjoyed this article, please support our award-winning journalism. Subscribe. By purchasing a subscription, you help ensure a future of influential stories about the discoveries and ideas shaping the world today.
Rainer Gamma is one of the largest and best-studied lunar spirals. It is a flattened oval like a staring eye, more than 100 kilometers wide, with two long, thin tails stretching out for hundreds of kilometers from each end. This makes it large enough to be seen even with a small telescope. In fact, I have seen it myself! At the time I was amazed that such a beautiful and striking feature could still not be explained.
Photograph showing Rainer Gamma, a “Moon Vortex” near the right edge of the Moon. Taken using a 20 cm telescope and a cell phone camera.
The remarkable brightness of the moon’s spirals turns out to be an important clue that explains what they are and where they came from. Surface material darkens over time as radiation from the Sun bathes it. A rule of thumb is that the brighter something is on the moon, the younger it is. Look, for example, at the glowing, feathery “rays” of relatively new material that splash around the giant craters. Tychoformed about 100 million years ago. From the Moon’s perspective, it was practically yesterday, since the Moon’s surface is billions of years old and essentially static compared to Earth.
During the Apollo era, scientists speculated that the swirls might be material ejected by recent volcanic activity. But maps of the Moon’s magnetic field (Created with data Apollo 15 and 16) show that the spirals all coincide with regions of slightly stronger magnetism, suggesting a different, more complex origin. To understand how this relates to the brightness of the spirals, we need to briefly look at the history of the Moon and the geophysics of its magnetic field.
Unlike Earth, the Moon currently has no global magnetic field. It had a weak magnetic field billions of years ago when it was still molten, but this weakened rapidly as the Moon cooled. But as the rocks on its surface solidified, they were able to retain some of their temporary magnetism, forming localized areas with slightly stronger, more permanent fields. These are called “relic” fields because of their ancient origin, and many are associated with lunar spirals.
The real reason for this link became clear when scientists published their findings about 10 years ago. Nature Communications The relic field around the vortex is weak, but slightly Deflect the solar wind Solar wind bombards the Moon’s surface. This wind is made up of subatomic particles from the Sun, and the magnetic field causes the trajectories of electrically charged particles like electrons and protons to change. In places where the residual magnetic field is strong, the particles are deflected to the side, darkening the ground where they fall, and leaving strange swirling patterns on the cleaner, magnetically shielded surface.
Surprisingly, the rule of thumb for the Moon that bright means young doesn’t always hold true. Sometimes bright means it has avoided the aging effects of cosmic radiation.
I remember reading the research paper with delight and having a smile on my face. Star Trek The fan in me was thrilled. The moon swirls were a reminder that our moon is Deflector Shield—Force field!
You might be thinking: Yes, the spirals have a magnetic effect. But why are they so long and winding? Further research in 2018 revealed that The source of the magnetic field that creates the vortex must be shallow.at a depth of less than three kilometers below the surface. This indicates that the whirlpools trace buried geological features formed by ancient lunar volcanism: lava tubes, rills and dikes. Rills are long, shallow grooves carved by flowing lava. Sometimes, as the flowing lava cools, it builds a roof of solid rock over it, forming an underground lava tube. Some whirlpools have been found near lava tubes. There are whirlpools in Mare Ingenii (“Sea of Wisdom”), Holes in the surface reveal lava tubes beneathA dike is a geological feature where magma intrudes between existing layers of rock and cools to form a large sheet-like structure.
If rocks with such structures have residual magnetic fields, they could generate vortices on the surface, a team of scientists reported in a paper published in 2024. Journal of Geophysical Research: Planets They suggest that deposits of ilmenite, a mineral common in lunar magma, could increase the local abundance of elements such as iron and nickel in the dikes, amplifying the amount of magnetism in the area.
This paints a good overall picture of whirlpools and how they form, but of course there are still unanswered questions. Planetary Science Journal There teeth Some Topographical changes in the vortexOn average, the brighter parts of the spirals tend to be several meters lower in altitude than the darker parts. It’s not yet clear why this is the case, and the scientists note in the paper that the underlying cause of the discoloration is still unknown. Decisively Although the solar wind remains the leading candidate, other models propose that the difference in colour could be due to material scattered by comets, or electrostatically charged dust particles kicked up by tiny meteorite impacts, either of which are then sorted by the Moon’s residual magnetic field.
To me, the real message of the Moon’s complicated origin story is quite simple: the Moon is literally the closest object to Earth in the entire universe, yet there is still much we don’t understand about it. That’s a reason for excitement, not discouragement. Building on our first visit to the Moon over half a century ago, as we explore it in more detail, perhaps even to actually visit it, we will have the opportunity to solve more of its mysteries, including some that perplex us.
