Anna Mittelholz


Last Name

Mittelholz

First Name

Anna

ORCID

0000-0002-5603-7334

Organisational unit

03476 - Giardini, Domenico / Giardini, Domenico

Filters

2025 - 20264
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Publications 1 - 4 of 4
  • LunarLeaper—A mission concept to explore the lunar subsurface with a small-scale legged robot
    Item type: Journal Article
    Kolvenbach, Hendrik; Mittelholz, Anna; Stähler, Simon Christian; et al. (2026)
    Acta Astronautica
    We present the LunarLeaper mission concept, which aims to robotically investigate volcanic pits on the lunar surface. Volcanic pits, or skylights, are collapse features that may provide access to subsurface lava tubes, which could serve as shelters for future human explorers and offer insight into the volcanic history of the Moon by exposing ancient lava flows. The existence and extent of large caves are still debated today and require in situ analysis. The Marius Hills site in particular offers a potential entry point to a cave system in a volcanic region on the lunar nearside. Our mission aims to deploy a payload-equipped 15 kg-class legged robot that can approach a pit, such as the Marius Hills pit, while taking measurements during the traverse. During the mission, measurements from a ground-penetrating radar (GPR) and a gravimeter will allow us to survey the subsurface and map any underlying lava tube, if present. The mission will investigate key questions regarding lunar volcanism, such as the existence and geometry of subsurface caves and the magnitude and timing of lava flows, while assessing the site's suitability for future human utilization and habitation. Furthermore, the mission will demonstrate key enabling technologies such as legged robots, serving as building blocks for the next generation of planetary missions.
  • Scales of Martian Crustal Magnetization Constrained by MAVEN, InSight, and Zhurong
    Item type: Journal Article
    Romeo, Orlando M.; Manga, Michael; Lillis, Robert J.; et al. (2025)
    Journal of Geophysical Research: Planets
    While Mars does not possess a currently active geodynamo, remanent crustal magnetization has been found across the planet and contains records of the origin, scale, and timing of Martian magnetization. The first in situ measurements of the Martian magnetic field on the planet's surface, at the InSight and Zhurong landing sites, allow for better constraints on magnetization coherence and depth scales near the surface, as crustal fields are closely related to a variety of geological and topographic features. We develop Monte Carlo models of the Martian crustal magnetization near the two landing sites on small-scales (<50 km) to meso-scales (100 - 1,000 km) to compute altitude profiles of the magnetic field intensity. We compare our simulations with the Langlais et al. (2019, https://doi.org/10.1029/2018je005854) crustal field model and surface measurements, indicating that power law distributions more accurately describe Martian altitude profiles compared to Gaussian models. Observations are best explained by fractal parameter β values near 2.7 and coherence scales roughly 250 km near InSight, with larger coherence scales and possibly thicker crustal magnetization near Zhurong. Motivated by these length scales, we create additional magnetization models based on the geological units near each lander to relate them to different time periods of Martian history. Our results suggest at least one polar field reversal in Martian history based on the simulated magnetization near the North-South dichotomy boundary. Furthermore, we propose that the Martian geodynamo might have weakened or suspended during the late Noachian, followed by revitalization of the core dynamo during the Hesperian period.
  • Modeling the Crustal Magnetic Field of Mars With Physics-Informed Neural Networks
    Item type: Journal Article
    Delcourt, Timothée; Mittelholz, Anna (2025)
    Journal of Geophysical Research: Planets
    Satellites orbiting Mars have measured crustal magnetic fields up to two orders of magnitude stronger than those on Earth. Although Mars currently lacks an active global magnetic field, this magnetization preserves a valuable record of the planet's early dynamo activity and crustal evolution. We present a high-resolution model of the crustal magnetic field of Mars, using all currently available magnetic field data collected by the MGS and MAVEN spacecraft (up to 02/2025), combined with a novel modeling approach. Notably, we incorporate recent low-altitude MAVEN data which contain short wavelength signals that were not available for previous models. We show that neural networks trained from spacecraft data can accurately predict the magnetic field at any location around Mars at orbital altitudes. These physics-informed networks use the equations of magnetostatics to enforce the conservative and solenoidal nature of the field, and are enhanced with bagging to mitigate the effect of noise in the data. Using this ensemble approach, we provide an estimate of uncertainties associated with our predictions. To demonstrate the performance of this method, we benchmark it against previous models using the same input and validation data subsets. Our model achieves an unprecedented resolution of spherical harmonics degree 139, corresponding to a spatial resolution of 153 km at the surface. Using our model to investigate small scale magnetic field signatures, we find that magnetic fields over ancient paleolakes are significantly stronger than other surface features or geological units, suggesting that serpentinization may have played a key role in magnetizing the crust.
  • LunarLeaper: From Simulation to Hardware for Lunar Legged Locomotion
    Item type: Conference Paper
    Church, Joseph; Fuhrer, Adrian; Fischer, Oliver; et al. (2025)
    IAC 2025 Congress Proceedings
    Following a successful Mission Concept Review in April 2025, the LunarLeaper team is advancing the design of a ~15 kg legged robot for investigation of a lunar volcanic pit. The review established Level 0/1 requirements and a concept of operations, while highlighting key challenges in locomotion maturity (TRL 4), power and thermal margins, and dust mitigation. To address these challenges, we are conducting interconnected studies that include morphology analyses, learning-based locomotion control, actuator and thermal modeling, and simulations of regolith interaction. Together, these activities form a framework that links morphology, actuation, control, and environment to mission level feasibility. By exposing key sensitivities of a legged robot, they enable better-informed Level 2/3 requirements, provide the foundation for the upcoming System Requirements Review (SRR), and establish a path toward hardware designs in Phase B.
Publications 1 - 4 of 4