The research centers on Milanković cycles, the periodic variations in Earth’s orbital eccentricity, axial tilt, and precession that redistribute the sunlight reaching the planet and thereby pace long-term climate change. In the modern Solar System, these cycles operate on well-known timescales, and they have been used to calibrate the geological time scale for the Cenozoic era with remarkable accuracy. Extending that approach into the Precambrian, however, has been hampered by a fundamental problem: numerical models of the Solar System’s orbital motion become chaotic and lose predictive power over tens of millions of years, and no astronomical solution can currently be trusted beyond roughly the last 100 million years. For intervals more than a billion years in the past, scientists have had to rely on theory alone to estimate how orbital frequencies differed from today’s values.

Sedimentary rocks offer a way around this limitation. When climate cycles driven by orbital variations imprint regular patterns on accumulating sediment—alternations between more resistant and more recessive beds, for example, or rhythmic changes in grain size and composition—the resulting cyclostratigraphy can be read as a recording of the astronomical forcing that produced it. The Hakatai Shale, deposited in shallow-water settings roughly 1.4 to 1.1 billion years ago during the Mesoproterozoic era, preserves such rhythms in striking detail. The team logged and analyzed stratigraphic sections at Red Canyon and Tapeats Creek within Grand Canyon National Park, conducting fieldwork under permit from the National Park Service, and measured the thickness and character of successive sedimentary cycles with centimeter-scale resolution.

The key to interpreting these rhythms lies in the physics of the Earth–Moon system. Tidal friction, the braking effect of lunar tides on Earth’s rotation, has steadily slowed the planet’s spin over geological time while pushing the Moon gradually farther away. As the day lengthens, the frequency of the climatic precession cycle—the wobble in Earth’s axis that changes how seasons align with the planet’s position around the Sun—changes in a predictable way. Because the precession signal modulates the amplitude of the eccentricity cycle, sedimentary records that capture both can be used to solve for the precession constant and, from it, the ancient Earth–Moon distance and length of day. This approach, known as TimeOpt and its Bayesian extension TimeOptBMCMC, was applied to the Hakatai Shale using the Astrochron software package, with 100,000 Monte Carlo samples used to constrain the statistical uncertainty of the reconstruction.

The analysis of the Tapeats Creek composite record, corrected for variations in sediment thickness, revealed a coherent suite of astronomical signals. The team identified cycles corresponding to climatic precession, orbital eccentricity, and obliquity, and used the ratios among them to test which cyclostratigraphic interpretation best fit the data. Among three competing interpretations of the dominant spectral peaks, the preferred option yielded sedimentation rates of a few centimeters per thousand years—values consistent with the quiet, low-energy depositional environments inferred independently from the rock’s lithology, which includes reworked microbial mat fabrics, wind-blown quartz grains, and pseudomorphs after evaporite minerals such as gypsum and anhydrite.

Beyond confirming that Milanković forcing operated in the Mesoproterozoic, the record delivered a surprise. The relative amplitudes of the astronomical forcing frequencies, particularly obliquity—the tilt of Earth’s spin axis—showed anomalous patterns compared with what present-day dynamics would predict. In the spectra of the Hakatai Shale, the strength of individual obliquity-related peaks shifted between different stratigraphic intervals in ways that mirror the behavior of state-of-the-art deep-time astronomical models, specifically the ZB23 solutions developed by Zeebe and colleagues, which extend orbital calculations back 3.5 billion years. In those models, the dominance of particular obliquity cycles changes through time as secular resonances among the planets drift in and out of critical configurations.

One such configuration involves the resonance angle associated with the motions of Mars and the inner planets, which can transiently disrupt the dominant obliquity cycle. Another involves a secular resonance that interferes with the main eccentricity cycle linked to the orbital frequencies of Earth and Jupiter. The Hakatai spectra show amplitude trends—weak expression of one eccentricity peak, enhanced power in a particular obliquity band—that are consistent with the models’ predictions for conditions around 1.2 billion years ago, including the possible influence of a resonance in which combinations of planetary orbital frequencies and Earth’s axial precession frequencies nearly coincide. The authors note that these patterns could also reflect a nonlinear climate response, in which interactions between multiple forcing frequencies generate combination tones that appear in the sedimentary record at sums and differences of the original periods.

Either interpretation carries weighty implications. If the amplitude anomalies record shifts in secular Solar System resonances, then the Grand Canyon strata provide the first empirical evidence from the rock record for how the gravitational architecture of the planetary system has changed over more than a billion years, complementing purely numerical approaches that are limited by chaos. If, instead, the signals arise from nonlinear climate dynamics, they illuminate how the Precambrian climate system responded to astronomical forcing in an atmosphere and ocean very different from today’s, before the rise of complex life and with substantially different greenhouse gas inventories. Distinguishing between these possibilities is a central goal of ongoing work, and the Bayesian inverse modeling framework applied here is designed to weigh such alternatives quantitatively.

The study builds on a growing effort to use geology as a probe of Solar System dynamics, sometimes described as mapping Solar System chaos with the geological record. Previous work by members of the team demonstrated that Milankovitch cycles preserved in 2.46-billion-year-old banded iron formations constrain the Earth–Moon system in the Paleoproterozoic, and theoretical studies have traced how tidal evolution reshaped the lunar orbit through resonant episodes. The Hakatai Shale now extends this empirical reach into the Mesoproterozoic with a record whose internal consistency—matching precession, eccentricity, and obliquity signals across two geographically separated sections—strengthens confidence that the rhythms are genuinely astronomical in origin rather than products of local tectonic or depositional noise.

The practical implications extend well beyond deep-time astronomy. Accurate knowledge of past astronomical frequencies underpins astrochronology, the dating method that uses orbital cycles to refine the geological time scale, and the new results constrain how those frequencies differed in the Precambrian, when shorter days and a closer Moon altered the pacing of climate cycles. The team’s cyclostratigraphic data and analyses have been made openly available through Zenodo, and the ZB23 astronomical solutions are publicly accessible, allowing other researchers to test and extend the reconstruction. As more ancient rhythmically deposited successions are examined with these tools, sedimentary rocks may continue to serve as long-term observatories of the heavens—recording, in ordinary mud, the slow gravitational conversation between Earth, the Moon, and the wandering planets.

Subject of Research: Reconstruction of Mesoproterozoic Earth–Moon dynamics and Solar System orbital evolution from Milanković cycles in Grand Canyon sedimentary strata

Article Title: Earth–Moon and Solar System history recorded in Mesoproterozoic Grand Canyon strata

Article References: Lantink, M. L., Eyster, A., Kocken, I. J., Meyers, S. R., & Zeebe, R. E. (2026). Earth–Moon and Solar System history recorded in Mesoproterozoic Grand Canyon strata. Nature Geoscience. https://doi.org/10.1038/s41561-026-02100-3

Image Credits: AI Generated

DOI: 10.1038/s41561-026-02100-3

Keywords: Milanković cycles, Hakatai Shale, Grand Canyon, Earth–Moon system, Mesoproterozoic, cyclostratigraphy, solar system dynamics, obliquity, lunar distance, astrochronology, secular resonance, tidal evolution

At the core of the IMAP payload is the Compact Dual Ion Composition Experiment (CoDICE), an innovative instrument developed and managed by SwRI. What sets CoDICE apart is its unparalleled ability to combine multiple measurement capabilities within a single patented sensor, allowing it to simultaneously analyze various ion populations in the heliosphere. This sophisticated instrument leverages advanced ion detection and spectrometry techniques to determine the distribution, mass, and composition of particles streaming through the boundary between solar and interstellar space, including interstellar pickup ions and solar wind ions associated with high-energy solar events.

The challenges of operating in the harsh environment of space, where temperatures can swing dramatically between the blistering heat of direct sunlight and the frigid cold of deep space, have been ingeniously addressed in CoDICE’s design. SwRI engineers devised a unique thermal management system for CoDICE whereby one side of the instrument is coated with a reflective “gold” surface that deflects intense solar radiation, while the opposite side bears a matte black finish engineered to absorb heat. This thermal dichotomy ensures the instrument’s components remain within operational temperature limits, safeguarding reliability and longevity throughout its mission lifespan.

Spanning roughly the size and weight of a standard five-gallon paint bucket, CoDICE packs cutting-edge technology into a compact 22-pound frame. Its innovative design not only optimizes space and weight constraints critical for spacecraft payloads but also exemplifies advances in sensor integration and miniaturization. Dr. Mihir Desai, a leading scientist on the IMAP team, highlights the elegant simplicity and robustness of this design, underscoring how it advances the frontier of space instrumentation.

Beyond CoDICE, SwRI’s contributions to IMAP extend to other vital instruments. Notably, the Institute developed the IMAP-Hi and IMAP-Lo instruments responsible for detecting energetic neutral atoms (ENAs), elusive particles that reveal information about the boundaries of interstellar space. IMAP-Lo focuses on lower-energy neutral atoms with a single-pixel imager and a conversion subsystem crafted at SwRI, while IMAP-Hi traces higher-energy ENAs. These paired instruments, operating in tandem, provide a comprehensive, multi-energy perspective of particle environments far beyond what previous missions have delivered.

Moreover, SwRI engineered the high-voltage power supplies for the Solar Wind Electron (SWE) instrument, a device measuring thermal electron distributions within the solar wind. This capability is vital to understanding the solar wind’s plasma characteristics and its influence on near-Earth and planetary space weather. Additionally, SwRI built digital electronics components for four other IMAP instruments, cementing its role as a cornerstone in the successful execution of this complex mission.

IMAP represents the next evolution in NASA’s Solar Terrestrial Probes (STP) program, which seeks to deepen humanity’s grasp of heliophysics—the study of the Sun’s influence throughout the solar system. By charting the heliosphere’s precise shape, composition, and dynamic processes, IMAP will fill longstanding gaps in our understanding of how solar material interacts with the galaxy’s interstellar environment. This knowledge is crucial for forecasting space weather phenomena that pose risks to astronauts, satellites, and critical space infrastructure.

The interaction at the heliosphere’s edge forms a natural shield that modulates the influx of cosmic rays—high-energy particles accelerated from distant astrophysical sources—that can be hazardous to both space missions and terrestrial technologies. IMAP’s detailed measurements will clarify how this barrier operates and how energetic particles are accelerated across vast interplanetary distances. Such insights are key to advancing protective technologies and mission planning for future deep-space exploration.

Led by Princeton University’s Professor David J. McComas and supported by a consortium of 27 institutions world-wide, the IMAP mission encapsulates a monumental collaborative effort. The Johns Hopkins Applied Physics Laboratory in Maryland designed and built the spacecraft and will oversee mission operations once IMAP embarks on its quest through space. This joint enterprise underscores the intersection of scientific innovation, engineering prowess, and international cooperation necessary for tackling today’s most pressing questions in space science.

SwRI’s leadership in managing the payload office and delivering cutting-edge instruments underscores its integral role in this historic mission. Spearheading the efforts, Executive Director Susan Pope serves as IMAP’s payload manager, while Dr. Mark Tapley carries responsibilities as the payload systems engineer. Their leadership ensures the coordination and harmonious integration of all instruments, amplifying the mission’s scientific return by enabling coordinated, multi-instrument observations.

The extraordinary complexity of measuring charged and neutral particles across an extraordinarily vast spatial domain demands instruments that are reliable, highly sensitive, and capable of enduring harsh conditions. IMAP’s suite of instruments, many featuring novel designs and advanced materials, represents a leap forward in heliophysics instrumentation that will set the stage for future explorations. As the mission embarks on its multi-year survey, it promises to deepen humanity’s understanding of our cosmic neighborhood and the forces shaping it.

This mission comes at a pivotal time when understanding solar influences on space weather and planetary environments is critically important not only for scientific discovery but also for the practical protection of both Earth-bound and orbital technologies. With IMAP’s impending launch, the scientific community eagerly awaits the data that will illuminate the complex processes governing our heliospheric boundary and the interplay between the Sun and galaxy.

For further details on this transformative mission and SwRI’s instrumental contributions, interested readers can visit SwRI’s heliophysics research portal, which offers extensive resources on solar and space physics research initiatives. IMAP’s launch represents a landmark achievement in solar and interstellar exploration, one that will fuel scientific inquiry and technological development for decades to come.

Subject of Research:
NASA’s Interstellar Mapping and Acceleration Probe (IMAP) mission and the role of Southwest Research Institute in developing its payload instruments, with a focus on the Compact Dual Ion Composition Experiment (CoDICE).

Article Title:
Southwest Research Institute Pioneers Advanced Ion Composition Sensor for NASA’s IMAP Mission to Map the Heliosphere

News Publication Date:
September 22, 2025

Web References:
https://www.swri.org/markets/earth-space/space-research-technology/space-science/heliophysics?&utm_medium=referralutm_source=eurekalert!&utm_campaign=imap-pr

Image Credits:
Southwest Research Institute

Keywords

Solar physics, Heliosphere, Solar wind, Cosmic rays, Interstellar space