arXiv subjects

Mark P. Panning

Publications and source records attributed to Mark P. Panning.

10 recordsLinked to original sources

arXiv2025

Potential for Lunar Interior Science by the Gravitational-Wave Detector LILA

The Laser Interferometer Lunar Antenna (LILA), a concept for measuring sub-Hz gravitational waves on the Moon, would use laser strainmeters to obtain extremely sensitive strain measurements from 1 mHz to 1 Hz. With proposed strain sensitivities, LILA would also be able to measure the normal modes of the Moon from 1-10 mHz at high signal-to-noise ratio. Such measurements would enable significant advances in our understanding of both the spherically symmetric and even 3D deep internal structure of the Moon. Strainmeter measurements may even be able to detect the translational mode of the solid inner core of the Moon at frequencies below 0.1 mHz. Inertial seismometers, on the other hand, are unlikely to reach the performance of $\sim10^{-16}$ m/s$^2$/$\sqrt{\mathrm{Hz}}$ required to reliably detect normal modes below 5-10 mHz, even with optimistic assumptions on future projected performance.

physics.geo-ph↗

arXiv2025

Fundamental Noise and Gravitational-Wave Sensitivity of the Laser Interferometer Lunar Antenna (LILA)

The Earth's Moon presents a uniquely advantageous environment for detecting astrophysical gravitational waves (GWs) in the frequency range of millihertz to decihertz. Unlike Terrestrial GW detectors, the quiet seismic environment of the Moon does not impede detection in this band; in fact the ground motions of the Moon will be excited by GWs, making the Moon a resonant amplifier at low frequencies. The Laser Interferometer Lunar Antenna (LILA) mission aims to be limited by thermal Brownian noise in its optics across most target frequencies. By taking advantage of the lunar normal mode resonances, we show that the first phase of the mission, LILA Pioneer, achieves the GW sensitivity required to study astrophysical sources through the millihertz to decihertz range. The advanced phase of the mission, LILA Horizon, would increase GW sensitivity to the cosmological horizon in this band.

gr-qc↗

arXiv2021

The Lunar Geophysical Network Landing Sites Science Rationale

The Lunar Geophysical Network (LGN) mission is proposed to land on the Moon in 2030 and deploy packages at four locations to enable geophysical measurements for 6-10 years. Returning to the lunar surface with a long-lived geophysical network is a key next step to advance lunar and planetary science. LGN will greatly expand our primarily Apollo-based knowledge of the deep lunar interior by identifying and characterizing mantle melt layers, as well as core size and state. To meet the mission objectives, the instrument suite provides complementary seismic, geodetic, heat flow, and electromagnetic observations. We discuss the network landing site requirements and provide example sites that meet these requirements. Landing site selection will continue to be optimized throughout the formulation of this mission. Possible sites include the P-5 region within the Procellarum KREEP Terrane (PKT; (lat:$15^{\circ}$; long:$-35^{\circ}$), Schickard Basin (lat:$-44.3^{\circ}$; long:$-55.1^{\circ}$), Crisium Basin (lat:$18.5^{\circ}$; long:$61.8^{\circ}$), and the farside Korolev Basin (lat:$-2.4^{\circ}$; long:$-159.3^{\circ}$). Network optimization considers the best locations to observe seismic core phases, e.g., ScS and PKP. Ray path density and proximity to young fault scarps are also analyzed to provide increased opportunities for seismic observations. Geodetic constraints require the network to have at least three nearside stations at maximum limb distances. Heat flow and electromagnetic measurements should be obtained away from terrane boundaries and from magnetic anomalies at locations representative of global trends. An in-depth case study is provided for Crisium. In addition, we discuss the consequences for scientific return of less than optimal locations or number of stations.

astro-ph.EP↗

arXiv2020

On-deck seismology: Lessons from InSight for future planetary seismology

Before deploying to the surface of Mars, the short-period (SP) seismometer of the InSight mission operated on deck for a total of 48 hours. This dataset can be used to understand how deck-mounted seismometers can be used in future landed missions to Mars, Europa, and other planetary bodies. While operating on deck, the SP seismometer showed signals comparable to the Viking-2 seismometer near 3 Hz where the sensitivity of the Viking instrument peaked. Wind sensitivity showed similar patterns to the Viking instrument, although amplitudes on InSight were ~80% larger for a given wind velocity. However, during the low wind evening hours the instrument noise levels at frequencies between 0.1 and 1 Hz were comparable to quiet stations on Earth, although deployment to the surface below the Wind and Thermal Shield lowered installation noise by roughly 40 dB in acceleration power. With the observed noise levels and estimated seismicity rates for Mars, detection probability for quakes for a deck-mounted instrument are low enough that up to years of on-deck recordings may be necessary to observe an event. Because the noise is dominated by wind acting on the lander, though, deck-mounted seismometers may be more practical for deployment on airless bodies, and it is important to evaluate the seismicity of the target body and the specific design of the lander. Detection probabilities for operation on Europa reach over 99% for some proposed seismicity models for a similar duration of operation if noise levels are comparable to low-wind time periods on Mars.

physics.geo-ph↗

arXiv2019

Seismic Signals from Waves on Titan's Seas

Seismology is the main tool for inferring the deep interior structures of Earth and potentially also of other planetary bodies in the solar system. Terrestrial seismology is influenced by the presence of the ocean-generated microseismic signal, which sets a lower limit on the earthquake detection capabilities but also provides a strong energy source to infer the interior structure on scales from local to continental. Titan is the only other place in the solar system with permanent surface liquids and future lander missions there might carry a seismic package. Therefore, the presence of microseisms would be of great benefit for interior studies, but also for detecting storm-generated waves on the lakes remotely. We estimated the strength of microseismic signals on Titan, based on wind speeds predicted from modeled global circulation models interior structure. We find that storms of more than 2 m/s wind speed, would create a signal that is globally observable with a high-quality broadband sensor and observable to a thousand kilometer distance with a space-ready seismometer, such as the InSight instruments currently operating on the surface of Mars.

astro-ph.EP↗

arXiv2018

Seismic response of the Mars Curiosity Rover: Implications for future planetary seismology

Seismic measurements are an important tool for exploration of planetary interiors, but may not be included in missions due to perceived complexity in placement of sensitive instruments on the surface. To help address this concern, we assess the fidelity of recordings of ground motion by an instrument placed on the deck of the engineering model of the Mars Science Laboratory compared with an identical instrument placed on the ground directly beneath. Comparison of the recordings reveals clear recordings of teleseismic earthquakes on both instruments. The transfer function between the instruments demonstrates the deck instrument is affected by resonance frequencies of the lander, and does not faithfully record ground motion at these frequencies or higher. In addition, additional decoherence is observed near 1 Hz during periods of strong airflow due to air conditioning cycling. However, excellent coherence and a transfer function near 1 can be observed in the important seismic band between 2 and 30 seconds at all times and extending up to the lander resonances during the night time when air conditioning was not running. This suggests a deck-mounted seismic instrument may be able to provide valuable science return without requiring additional deployment complexity.

physics.geo-ph↗

arXiv2017

Seismic wave propagation in icy ocean worlds

Seismology was developed on Earth and shaped our model of the Earth's interior over the 20th century. With the exception of the Philae lander, all in situ extraterrestrial seismological effort to date was limited to other terrestrial planets. All have in common a rigid crust above a solid mantle. The coming years may see the installation of seismometers on Europa, Titan and Enceladus, so it is necessary to adapt seismological concepts to the setting of worlds with global oceans covered in ice. Here we use waveform analyses to identify and classify wave types, developing a lexicon for icy ocean world seismology intended to be useful to both seismologists and planetary scientists. We use results from spectral-element simulations of broadband seismic wavefields to adapt seismological concepts to icy ocean worlds. We present a concise naming scheme for seismic waves and an overview of the features of the seismic wavefield on Europa, Titan, Ganymede and Enceladus. In close connection with geophysical interior models, we analyze simulated seismic measurements of Europa and Titan that might be used to constrain geochemical parameters governing the habitability of a sub-ice ocean.

physics.geo-ph↗

arXiv2017

Expected seismicity and the seismic noise environment of Europa

Seismic data will be a vital geophysical constraint on internal structure of Europa if we land instruments on the surface. Quantifying expected seismic activity on Europa both in terms of large, recognizable signals and ambient background noise is important for understanding dynamics of the moon, as well as interpretation of potential future data. Seismic energy sources will likely include cracking in the ice shell and turbulent motion in the oceans. We define a range of models of seismic activity in Europa's ice shell by assuming each model follows a Gutenberg-Richter relationship with varying parameters. A range of cumulative seismic moment release between $10^{16}$ and $10^{18}$ Nm/yr is defined by scaling tidal dissipation energy to tectonic events on the Earth's moon. Random catalogs are generated and used to create synthetic continuous noise records through numerical wave propagation in thermodynamically self-consistent models of the interior structure of Europa. Spectral characteristics of the noise are calculated by determining probabilistic power spectral densities of the synthetic records. While the range of seismicity models predicts noise levels that vary by 80 dB, we show that most noise estimates are below the self-noise floor of high-frequency geophones, but may be recorded by more sensitive instruments. The largest expected signals exceed background noise by $\sim$50 dB. Noise records may allow for constraints on interior structure through autocorrelation. Models of seismic noise generated by pressure variations at the base of the ice shell due to turbulent motions in the subsurface ocean may also generate observable seismic noise.

astro-ph.EP↗

arXiv2017

Vital Signs: Seismology of ocean worlds

Ice-covered ocean worlds possess diverse energy sources and associated mechanisms that are capable of driving significant seismic activity, but to date no measurements of their seismic activity have been obtained. Such investigations could probe their transport properties and radial structures, with possibilities for locating and characterizing trapped liquids that may host life and yielding critical constraints on redox fluxes, and thus on habitability. Modeling efforts have examined seismic sources from tectonic fracturing and impacts. Here, we describe other possible seismic sources, their associations with science questions constraining habitability, and the feasibility of implementing such investigations. We argue, by analogy with the Moon, that detectable seismic activity on tidally flexed ocean worlds should occur frequently. Their ices fracture more easily than rocks, and dissipate more tidal energy than the <1 GW of the Moon and Mars. Icy ocean worlds also should create less thermal noise for a due to their greater distance and consequently smaller diurnal temperature variations. They also lack substantial atmospheres (except in the case of Titan) that would create additional noise. Thus, seismic experiments could be less complex and less susceptible to noise than prior or planned planetary seismology investigations of the Moon or Mars.

astro-ph.EP↗

arXiv2017

Geophysical tests for habitability in ice-covered ocean worlds

Geophysical measurements can reveal the structure of icy ocean worlds and cycling of volatiles. The associated density, temperature, sound speed, and electrical conductivity of such worlds thus characterizes their habitability. To explore the variability and correlation of these parameters, and to provide tools for planning and data analyses, we develop 1-D calculations of internal structure, which use available constraints on the thermodynamics of aqueous MgSO$_4$, NaCl (as seawater), and NH$_3$, water ices, and silicate content. Limits in available thermodynamic data narrow the parameter space that can be explored: insufficient coverage in pressure, temperature, and composition for end-member salinities of MgSO$_4$ and NaCl, and for relevant water ices; and a dearth of suitable data for aqueous mixtures of Na-Mg-Cl-SO$_4$-NH$_3$. For Europa, ocean compositions that are oxidized and dominated by MgSO$_4$, vs reduced (NaCl), illustrate these gaps, but also show the potential for diagnostic and measurable combinations of geophysical parameters. The low-density rocky core of Enceladus may comprise hydrated minerals, or anydrous minerals with high porosity comparable to Earth's upper mantle. Titan's ocean must be dense, but not necessarily saline, as previously noted, and may have little or no high-pressure ice at its base. Ganymede's silicious interior is deepest among all known ocean worlds, and may contain multiple phases of high-pressure ice, which will become buoyant if the ocean is sufficiently salty. Callisto's likely near-eutectic ocean cannot be adequately modeled using available data. Callisto may also lack high-pressure ices, but this cannot be confirmed due to uncertainty in its moment of inertia.

astro-ph.EP↗