{"id":986272,"date":"2026-05-26T17:00:20","date_gmt":"2026-05-26T17:00:20","guid":{"rendered":"https:\/\/www.europesays.com\/uk\/986272\/"},"modified":"2026-05-26T17:00:20","modified_gmt":"2026-05-26T17:00:20","slug":"jupiters-largest-moon-has-a-rare-magnetic-field-a-strange-theory-may-explain-it","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/uk\/986272\/","title":{"rendered":"Jupiter\u2019s Largest Moon Has a Rare Magnetic Field. A Strange Theory May Explain It"},"content":{"rendered":"

Jupiter, the biggest planet in our solar system, also hosts some of the biggest moons. That includes Ganymede<\/a>, which happens to be the only moon known to generate its own magnetic field. After much speculation about why, one team believes it finally has the answer.<\/p>\n

Recent research published in Science Advances<\/a> suggests that Ganymede\u2019s metallic core is still forming today, and this very process is what generates the moon\u2019s magnetic field. These conclusions are at odds with the conventional understanding that Ganymede\u2019s core formed about 4.5 billion years ago, at nearly the same time that the moon emerged. While the study doesn\u2019t completely reject previous theories, it does raise critical questions surrounding Ganymede\u2019s dynamo<\/a>, or the source of its magnetic field.<\/p>\n

\u201cDynamos are one of the few ways we can understand what\u2019s happening deep in a body\u2019s interior with spacecraft data,\u201d Kevin Trinh, the study\u2019s first author and a planetary scientist at the California Institute of Technology (Caltech), said in a statement<\/a>. \u201cCallisto, for example, is similar in size and density [to Ganymede], but it has no obvious evidence of a dynamo. Why are they so different?\u201d<\/p>\n

The buzzy enclosure <\/p>\n

Aside from its sheer size, Ganymede is also among the icy solar system moons that scientists are closely tracking for signs of water beneath their frozen shells<\/a>. But unlike Europa, Enceladus, and the like, Ganymede has its own magnetosphere\u2014the region surrounding a cosmic body dominated by its magnetic field\u2014which the Galileo spacecraft initially spotted in 1996<\/a>.<\/p>\n

Ever since this momentous discovery, scientists have proposed different ideas about Ganymede\u2019s dynamo. According to the new paper, these suggestions typically converged toward some kind of movement in Ganymede\u2019s metal core. However, the study added, they\u2019ve done so with \u201cconflicting assumptions on Ganymede\u2019s initial state.\u201d<\/p>\n

\"GanymedePossible thermal evolutionary paths of Ganymede\u2019s interior based on assumed initial temperatures. \u00a9 Trinh et al., 2026 <\/p>\n

\u201cMany formation studies suggest that Ganymede formed too cold to start with a metal core,\u201d Trinh, who completed the research as a PhD student at Arizona State University (ASU), explained in the ASU statement<\/a>. \u201cMeanwhile, many modeling studies of Ganymede\u2019s dynamo assume that Ganymede formed its metal core roughly when the moon itself formed, as Earth did. Both of these things cannot be simultaneously true.\u201d<\/p>\n

Tackling the conflict <\/p>\n

The latest study sought to address both possibilities. Trinh and colleagues simulated Ganymede\u2019s evolution from a \u201ccold start\u201d as opposed to immediately starting off with a hot core 4.5 billion years ago, as suggested by current models. For context, if current models are correct, it would mean that Ganymede\u2019s core is at present cooling off, and once it completely cools and solidifies, the dynamo would shut off.<\/p>\n

But the new simulations suggested otherwise, Trinh said in the Caltech statement. The \u201ccold start\u201d simulations revealed a \u201cnew mechanism that hadn\u2019t been identified before, challenging the notion that core-hosted dynamos necessarily arise from a cooling reservoir of constant size.\u201d<\/p>\n

In this scenario, a still-hot, still-forming liquid iron core inside Ganymede stirs the moon\u2019s dynamo while migrating downward. In fact, that\u2019s more consistent with Ganymede\u2019s formation models, which indicate that the moon was too cold to start with a metal core, Trinh explained in the ASU release.<\/p>\n

Growing and growing <\/p>\n

To be clear, the study isn\u2019t disproving conventional models. Obviously, we can\u2019t turn the cosmic clock back billions of years to verify simulations, so it may as well be that Ganymede was born with a metal core. Still, the results introduce a new interpretation of current observations that could fill some gaps in our knowledge of Ganymede\u2019s dynamo.<\/p>\n

Furthermore, the paper added, enhanced understanding of extraterrestrial dynamos \u201cnaturally\u201d raises other questions surrounding the formation of other moons of interest in the outer solar system, such as Europa or Callisto. Why did some large, icy moons fail to develop dynamos? Or did they have one in the distant past? Overall, what do different evolutionary trajectories tell us about cosmic history?<\/p>\n

Hopefully, we won\u2019t have to wait too long for the data to catch up to scientist inquiries. If things go as planned, NASA\u2019s Europa Clipper<\/a> and ESA\u2019s Juice<\/a> will send back some updated info on the Jovian system. So, as always, stay tuned!<\/p>\n","protected":false},"excerpt":{"rendered":"Jupiter, the biggest planet in our solar system, also hosts some of the biggest moons. That includes Ganymede,…\n","protected":false},"author":2,"featured_media":986273,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[3844],"tags":[129438,129439,17172,274198,3889,70,413,16,15],"class_list":["post-986272","post","type-post","status-publish","format-standard","has-post-thumbnail","category-space","tag-europa-clipper","tag-ganymede","tag-jupiter","tag-jupiter-icy-moons-explorer","tag-planetary-science","tag-science","tag-space","tag-uk","tag-united-kingdom"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@uk\/116641952941334753","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/986272","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/comments?post=986272"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/986272\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media\/986273"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media?parent=986272"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/categories?post=986272"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/tags?post=986272"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}