Apollo Rocks Reveal The Moon’s Magnetic Field Was Both Strong and Weak
Did the Moon have a strong magnetic field in its early history, or a weak one? Researchers have debated that question for years. A new study in Nature Geoscience now suggests the debate can finally be put to rest: the Moon experienced brief bursts of intense magnetism, but for most of its history, its field was weak.
The confusion, the researchers say, stems from where Apollo astronauts landed. All six missions touched down in regions rich in titanium-heavy volcanic rock, areas that happened to preserve evidence of short-lived magnetic surges, rather than the Moon’s typical, weaker state.
“Our new study suggests that the Apollo samples are biased to extremely rare events that lasted a few thousand years – but up to now, these have been interpreted as representing 0.5 billion years of lunar history. It now seems that a sampling bias prevented us from realising how short and rare these strong magnetism events were,” said lead author Claire Nichols in a press release.
How the Moon’s Early Magnetic Field Flickered
Many researchers struggled to reconcile the strong magnetism recorded in some Apollo samples with what they knew about the Moon’s interior. Compared with Earth, the Moon has a relatively small core, about one-seventh of its radius, which seems too small to sustain a powerful magnetic dynamo for long periods.
The new research proposes that the Moon didn’t maintain a strong field continuously. Instead, geological events inside the Moon temporarily supercharged it.
To investigate, the team analyzed mare basalts — dark volcanic rocks formed when lava rose from the Moon’s interior billions of years ago. They discovered that every sample that recorded a strong magnetic field also contained high levels of titanium. Samples with less than six percent titanium were consistently linked to weak magnetism.
Rather than sustaining a powerful magnetic shield for hundreds of millions of years, the Moon appears to have experienced brief, intense pulses.
Read More: Establishing a Moon Time Zone Could Benefit Future Missions to Mars
Why Apollo Samples Told an Incomplete Story
The titanium connection also helps explain why earlier interpretations leaned heavily toward a strong lunar magnetic past. The Apollo missions landed in relatively flat regions known as the lunar mare — plains formed by ancient volcanic lava flows — because they were safer for spacecraft, not because they were representative of the Moon as a whole.
Those mare regions happen to contain abundant titanium-rich basalts. As a result, astronauts brought back an outsized number of rocks that recorded the Moon’s rare magnetic surges.
“If we were aliens exploring the Earth, and had landed here just six times, we would probably have a similar sampling bias especially if we were selecting a flat surface to land on,” said co-author Jon Wade in the press release.
The team’s models suggest that if samples had been collected randomly across the lunar surface, most would show evidence of a weak magnetic field.
What Artemis Could Reveal Next
The findings not only clarify the Moon’s past but also offer predictions for future exploration. If the theory is correct, rocks collected from regions outside the mare basins should overwhelmingly record weak magnetism.
Upcoming Artemis missions aim to land astronauts in new parts of the Moon, potentially providing a broader cross-section of lunar geology.
“We are now able to predict which types of samples will preserve which magnetic field strengths on the Moon. The upcoming Artemis missions offer us an opportunity to test this hypothesis and delve further into the history of the lunar magnetic field,” added co-author Simon Stephenson.
Billions of years after those magnetic pulses flickered through its interior, the Moon’s rocks are still refining our understanding of how planetary dynamos begin, and how easily our conclusions can be shaped by where we happen to land.
Read More: NASA’s Artemis II Rocket Arrives at Launch Pad Ahead of Moon Mission
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a new study published in Nature Geoscience: An intermittent dynamo linked to high-titanium volcanism on the Moon