Neutrino Tomography of Earth: A New Look at the Planet's Interior ✛
Context
For nearly a century, Earth’s interior has been studied primarily through seismic waves, which are sensitive to the elastic properties of matter. These methods yielded the detailed PREM model, yet they rely on the macroscopic response of matter to gravitational and elastic forces. Neutrinos, predicted by Wolfgang Pauli almost a century ago, interact exclusively through the weak force, opening an additional window. Their ability to penetrate the planet’s bulk, partially absorbed depending on the density traversed, resembles the transit spectroscopy method used to study exoplanet atmospheres—except here, instead of a star, it’s the atmosphere, and instead of a planet, it’s Earth itself.
Methods
The analysis is based on data collected by the IceCube neutrino telescope at the South Pole. The detector registers Cherenkov radiation—flashes of light produced when charged particles travel through the ice faster than light in that medium. By measuring the flux attenuation as a function of energy, the researchers apply a kind of spectroscopy of Earth: different neutrino energies are sensitive to different depths. Out of 368,071 recorded tracks from neutrino interactions, events with energies from 500 GeV to 100 TeV were selected. For each event, the energy and zenith angle were reconstructed, the latter determining the path length through Earth. To link the observed flux attenuation to density, Earth was parameterized as a set of concentric shells of constant density. Then, using Monte Carlo methods and Bayesian analysis, by varying density parameters and numerous systematic uncertainties (including neutrino fluxes, interaction cross-section, and ice properties), a joint probability distribution was constructed.
Results
The reconstructed radial density profile, shown in Figure 2, agrees well with the standard seismic PREM model. The densities of the core, mantle, and crust, determined to within tens of percent, lie within expected ranges. From this profile, Earth’s mass was calculated: 7.25×1024 kg (68% confidence interval [6.31, 8.31]×1024 kg), which encompasses the gravitationally measured value of 5.97×1024 kg within the 95% interval. Similarly, the polar moment of inertia was found to be 1.05×1038 kg·m² ([9.04×1037, 1.24×1038] kg·m²), also consistent with the reference value of 8.01×1037 kg·m². This result is the most precise measurement to date of Earth’s internal structure using the weak interaction.
Implications
The success of neutrino tomography ushers in a new era in planetary science. We can now test models of Earth’s structure without relying solely on elastic waves and gravity. This method is especially valuable because it is based on an interaction described with high precision by the Standard Model of particle physics—the neutrino-nucleon cross-section is determined by the properties of partons inside protons and neutrons. Thus, geophysics gains a tool calibrated by the physics of the microcosm. Moreover, neutrino tomography could eventually be applied to other planets if sufficiently powerful detectors become available.
Future development
The near future of the method lies in increased statistics and reduced systematic uncertainties. The already planned IceCube upgrade and the under-construction Mediterranean telescope KM3NeT will boost the number of detected neutrinos, especially at high energies. Meanwhile, data on fluxes of atmospheric and astrophysical neutrinos, produced in objects like supernovae, neutron stars, and pulsars, as well as around black holes, are being refined. Improved models of nuclear effects in cross-sections at low Bjorken-x will help reduce uncertainties related to parton shadowing in nuclei.
Impact
Neutrino tomography will impact geophysics by providing an independent check on models of Earth’s interior; particle physics by stimulating more precise measurements of neutrino-nucleon cross-sections; and astrophysics, since it requires detailed knowledge of astrophysical neutrino fluxes, whose sources may include accreting black holes and exploding stars.
Next steps
Next steps include analyzing IceCube data with improved calibration of ice properties and incorporating information on neutrino oscillations (though negligible in this energy range). Joint fits with other experiments are also planned to reduce cross-section uncertainties.
Key open problems
Neutrino tomography is directly linked to the mystery of the composition and dynamics of Earth’s core, which generates the magnetic field. It may also help understand why Mars, a similar planet, lacks a global field. Moreover, the method bridges geophysics and particle physics, testing predictions of the Standard Model using an enormous nuclear target—Earth itself.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The study uses data from the IceCube neutrino telescope to reconstruct the radial density profile of the Earth. From 368,071 recorded tracks, events with energies from 500 GeV to 100 TeV were selected, and Monte Carlo and Bayesian analysis were used to estimate the density of the Earth's shells. The obtained profile is consistent with the PREM model, and the computed mass and moment of inertia agree with reference values within uncertainties.
Where its strength is
The strength of the work lies in the fact that neutrino tomography relies on the weak interaction, which is independent of the elastic properties of matter, providing an additional channel to test models of Earth's structure. This is the first measurement of the planet's internal structure with precision down to tens of percent based solely on neutrino data.
Where it could go next
- It might be interesting to see how the neutrino tomography method could be applied to study the distribution of dark matter inside the Earth, if one looks for an excess of neutrinos from annihilation of dark matter particles captured by the planet's gravity in IceCube data.based on: Symphony of Shadows: Neutrino Telescopes Catch the Whisper of Dark Matter arXiv:2607.05335v1
- A related idea is to use neutrinos to study the geothermal flux: if one analyzes the geoneutrino flux in a way analogous to the attenuation of the flux through the Earth, one could obtain an independent estimate of the radioactive element content in the mantle and crust.based on: An Underwater Hunter for Earth's Heat arXiv:2606.20780
- One could consider applying the approach to other dense objects, such as mountain ranges: using muon tomography, one could obtain high-resolution images of internal structure, and then compare with neutrino tomography for calibration.based on: How to Catch Ghost Neutrinos in the Mountains arXiv:2607.26128v1
Worth trying
- Test whether the accuracy of density reconstruction can be improved by adding geoneutrinos to the analysis, which provide information about radioactive heat production in the interior.
- Try a joint analysis of neutrino and seismic data to refine the PREM model in transition zones.
- Use IceCube data to search for density anomalies associated with possible heterogeneities in the mantle, such as large low-shear-velocity provinces.
Why this may matter
This method could become an independent tool for verifying geophysical models, and in the future, a way to study the composition and thermal history of the Earth without relying on assumptions about elastic properties.
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Original abstract
as written by the authors arXiv:2607.02644v2
The Earth's interior reflects its geological evolution, from accretion to present-day dynamics. Its structure drives the geodynamo in the outer core, generating the magnetic field that shields the surface from charged cosmic radiation. The primary observables of the Earth's interior are its radial density distribution and derived quantities such as its mass and moment of inertia. These have traditionally been inferred from gravity and seismic wave propagation, which probe the macroscopic response of matter to gravitational and elastic forces. Here we instead constrain the Earth's density profile using high-energy neutrinos observed by the IceCube Neutrino Observatory at the South Pole. We analyze 10.7 years of predominantly muon-neutrino data spanning 500 GeV--100 TeV, including atmospheric neutrinos produced by cosmic-ray interactions in the Earth's atmosphere and the diffuse astrophysical neutrino flux. Neutrino attenuation depends on both the traversed column density and neutrino energy. By measuring the zenith- and energy-dependent flux suppression, we infer the Earth's radial density profile by fitting a concentric uniform-density shell model that incorporates neutrino fluxes, interaction cross sections, detector response, and glacial-ice systematic uncertainties. From the resulting density posteriors, we derive the Earth's mass and polar moment of inertia as measured by neutrinos. These are the most precise weak-interaction measurements of these quantities to date and are consistent with the Preliminary Reference Earth Model and independent gravitational determinations. Our results demonstrate that neutrinos provide a novel probe of planetary interiors via a distinct physical interaction, complementing gravity and seismology. With improved detectors and precision, neutrinos will further contribute to a multifaceted understanding of the Earth's structure.
To detect a single neutrino, you would need a lead wall one light-year thick; yet Earth can attenuate a beam of 100 TeV neutrinos by almost half if they pass through the core.
Key numbers
- Years of data: 10.7 years
- Number of events: 368 071
- Energy range: 500 GeV – 100 TeV
- Measured mass of Earth: 7.25×1024 kg
- Measured moment of inertia: 1.05×1038 kg·m²