{"id":548358,"date":"2026-03-20T05:41:12","date_gmt":"2026-03-20T05:41:12","guid":{"rendered":"https:\/\/www.newsbeep.com\/ca\/548358\/"},"modified":"2026-03-20T05:41:12","modified_gmt":"2026-03-20T05:41:12","slug":"apollo-samples-told-a-conflicting-story-about-lunar-magnetism-until-now","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/ca\/548358\/","title":{"rendered":"Apollo Samples Told a Conflicting Story About Lunar Magnetism, Until Now"},"content":{"rendered":"

Scientists know that since about 900 million years ago, our Moon has had no magnetic field, and data from lunar soil<\/a> and observations of lunar crust show that it had either a weak or nonexistent magnetic field even before then. But Moon rocks from NASA\u2019s Apollo missions<\/a> indicated the opposite, recording strangely strong magnetism during the Moon\u2019s early history between 3.5 billion and 3.9 billion years ago.<\/p>\n

The Moon\u2019s inner core is only about one seventh the size (radius) of the Moon itself, meaning that it would be difficult for the Moon to create a dynamo<\/a> strong enough to explain the magnetism measured in the Apollo samples. (For comparison, Earth\u2019s inner core is about 20% of our planet\u2019s radius.)<\/p>\n

\u201cThese two conflicting stories just keep fighting each other.\u201d<\/p>\n

This discrepancy raised a question for paleomagnetists: Was the Moon\u2019s magnetic field truly weak or truly strong in its early history? \u201cThese two conflicting stories,\u201d said Claire Nichols<\/a>, a paleomagnetist at the University of Oxford, \u201cjust keep fighting each other.\u201d<\/p>\n

The question inspired Nichols and her team to analyze data from Apollo missions once more. Their results, published in Nature Geoscience<\/a>, show that both understandings of lunar samples are partly right: The Moon\u2019s early magnetic field was probably mostly weak or nonexistent, punctuated by very short bursts of strong magnetism.<\/p>\n

The study is \u201can important step forward, because it\u2019s a work that recognizes both the evidence for the presence and the absence of a magnetic field on the Moon,\u201d said John Tarduno<\/a>, a geophysicist at the University of Rochester who was not involved in the new study.<\/p>\n

Revisiting Apollo Samples<\/p>\n

Many Apollo samples consist of rocks known as mare basalts. Mare basalts are found on the flat plains (lunar maria) that provided suitable landing sites for most of Apollo\u2019s lunar modules, and that\u2019s where astronauts collected most samples.<\/p>\n

In the new study, researchers investigated whether a link existed between the intense magnetism of the Apollo samples and their composition. This approach was \u201creally interesting,\u201d explained Sabine Stanley<\/a>, a planetary scientist at Johns Hopkins University, because it allowed scientists to ask the question of \u201cwhere did these rocks come from, as opposed to what\u2019s carrying the magnetism.\u201d Stanley was not involved in the new research.<\/p>\n

The team found that large amounts of titanium in the Apollo samples correlated with evidence of increased magnetism on the Moon. This result pointed to one likely explanation: The formation of these titanium-rich basalts was somehow linked to the temporary generation of strong magnetic fields.<\/p>\n

\u201cI was pretty blown away,\u201d Nichols said. \u201cSuddenly, it all makes sense.\u201d Scientists can now \u201cactually explain\u201d every paleomagnetic observation from the Moon between 3.5 billion and 3.9 billion years ago, she said.<\/p>\n

Modeling Magnetism<\/p>\n

But what exactly was the relationship between Apollo\u2019s titanium-rich basalts and instances of strong lunar magnetism?<\/p>\n

To answer that question, the researchers used existing models<\/a> that simulated the Moon\u2019s interior.<\/p>\n

The models showed the lunar core could feasibly generate strong magnetic fields when titanium-rich material melted at the boundary between the Moon\u2019s core and mantle. This melting would spur high heat transfer (also called heat flux) across the boundary and create a strong dynamo. However, such a process would be possible only if the melting events were very short\u2014less than 5,000 years. Longer melting periods would not be able to generate high enough heat transfers across the core-mantle boundary to create a strong magnetic field, Nichols said.<\/p>\n

\"A<\/p>\n

\t\tThe authors\u2019 drawing shows the structure of the Moon\u2019s interior without a strong magnetic field (left) and with one (right). The scenario at right explains the formation of the Moon\u2019s strong dynamo and the creation of the high-titanium basalts that make up most Apollo samples. In this scenario, high-titanium (High Ti) material falls to the core-mantle boundary, creating a temporary heat flux that forms a strong dynamo and a short-lived magnetic field. Magma created from that melting process then erupts at the Moon\u2019s surface, producing high-titanium basalts. KREEP, identified at both the crust-mantle and core-mantle boundary in this illustration, is material enriched in potassium (K), rare earth elements (REE), and phosphorus (P). Credit: Nichols et al., 2026, https:\/\/doi.org\/10.1038\/s41561-026-01929-y<\/a><\/p>\n

The results indicate that the Apollo samples are likely highly biased, meaning they document very brief periods of strong magnetism in the Moon\u2019s early history, and do not record the hundreds of millions of years of weak or nonexistent lunar magnetism, according to the authors.<\/p>\n

The new study is \u201ca really nice systematic analysis to say that there really is a strong correlation [of lunar magnetism] to these high-titanium basalts, and looking for a causal mechanism related to those makes total sense,\u201d Stanley said. However, \u201cthere\u2019s a lot of work that needs to be done to see whether or not all the processes and timings that [the authors] are suggesting will actually work,\u201d she added.<\/p>\n

Heat flux \u201cis only one criterion for a dynamo,\u201d Tarduno said. \u201cThere are other things you have to consider.\u201d<\/p>\n

Tarduno, who said he liked the ideas proposed in the paper, agreed. The researchers\u2019 description\u2014of short, discrete melting events that cause strong lunar dynamos\u2014works well to explain the paleomagnetic evidence, he said. But additional factors, such as the magnetic and hydrodynamic properties and the geometry of the Moon\u2019s interior, should be added to more sophisticated models and dynamo simulations to further test whether that explanation is likely. Heat flux \u201cis only one criterion for a dynamo,\u201d he said. \u201cThere are other things you have to consider.\u201d<\/p>\n

Timing also needs to be better defined, Stanley said. The speed at which the mass of titanium-rich material sank to the Moon\u2019s core, melted, and then rose back to the Moon\u2019s surface would have determined the intensity of the magnetism of Apollo samples, so clarifying the timeline of mare basalt formation is critical.<\/p>\n

Experiments on the lunar surface and additional sampling of Moon rocks, perhaps from future Artemis missions<\/a>, may offer further insight into the origin of the Moon\u2019s early magnetism, Tarduno said.<\/p>\n

\u201cIt\u2019s going to really depend on what the composition and structure of the Moon\u2019s mantle is, which we need more information on,\u201d Stanley said.<\/p>\n

\u2014Grace van Deelen (@gvd.bsky.social<\/a>), Staff Writer<\/p>\n

Citation:\u00a0van Deelen, G. (2026), Apollo samples told a conflicting story about lunar magnetism, until now,\u00a0Eos, 107, https:\/\/doi.org\/10.1029\/2026EO260094<\/a>. Published on 19 March 2026.<\/p>\n

Text \u00a9 2026. AGU.\u00a0CC BY-NC-ND 3.0<\/a>
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.<\/p>\n

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