Moon Research Articles

A Synchronous Moon as a Possible Cause of Mars' Initial Triaxiality

AbstractThe paper addresses the possibility of a young Mars having had a massive moon, which synchronized the rotation of Mars, and gave Mars an initial asymmetric triaxiality to be later boosted by geological processes. It turns out that a moon of less than a third of the lunar mass was capable of producing a sufficient initial triaxiality. The asymmetry of the initial tidal shape of the equator depends on timing: the initial asymmetry is much stronger if the synchronous moon shows up already at the magma‐ocean stage. From the moment of synchronization of Mars' rotation with the moon's orbital motion, and until the moon was eliminated (as one possibility, by an impact in the beginning of the Late Heavy Bombardment), the moon was sustaining an early value of Mars' rotation rate.

Hints of Planet Formation Signatures in a Large-cavity Disk Studied in the AGE-PRO ALMA Large Program

Detecting planet signatures in protoplanetary disks is fundamental to understanding how and where planets form. In this work, we report dust and gas observational hints of planet formation in the disk around 2MASS J16120668-301027, as part of the Atacama Large Millimeter/submillimeter Array (ALMA) Large Program “AGE-PRO: ALMA survey of Gas Evolution in Protoplanetary disks.” The disk was imaged with the ALMA at Band 6 (1.3 mm) in dust continuum emission and four molecular lines: 12CO(J = 2–1), 13CO(J = 2–1), C18O(J = 2–1), and H2CO(J = 3(3,0)–2(2,0)). Resolved observations of the dust continuum emission (angular resolution of ∼150 mas, 20 au) show a ring-like structure with a peak at 0.″57 (75 au), a deep gap with a minimum at 0.″24 (31 au), an inner disk, a bridge connecting the inner disk and the outer ring, along with a spiral arm structure, and a tentative detection (to 3σ) of a compact emission at the center of the disk gap, with an estimated dust mass of ∼2.7−12.9 Lunar masses. We also detected a kinematic kink (not coincident with any dust substructure) through several 12CO channel maps (angular resolution ∼200 mas, 30 au), located at a radius of ∼0.″875 (115.6 au). After modeling the 12CO velocity rotation around the protostar, we identified a purple tentative rotating-like structure at the kink location with a geometry similar to that of the disk. We discuss potential explanations for the dust and gas substructures observed in the disk and their potential connection to signatures of planet formation.

A Method for Constructing Low-Energy Trajectories for Earth–Moon Transfers

A Method for Constructing Low-Energy Trajectories for Earth–Moon Transfers

Space debris in vicinity of collinear libration points of the Earth–Moon system

Practical space exploration has a priority the issues of safety of space missions. And an important fundamental problem arises — the study of the evolution and the stability of a space debris cloud, consisting of artificial objects remnants, or debris of extra-terrestrial origin.We discuss a new behavior of mechanical system near an unstable equilibrium position — the trajectories located in the selected neighborhood of unstable equilibrium. As an important application, we consider perturbed motion in collinear libration points vicinity of the restricted circular three-body problem.Numerical simulations for the parameters of the Earth–Moon system convincingly illustrate our theoretical study. This mathematical model allows us predicting how long the debris with certain energy can fly in vicinity of unstable collinear libration point, being close to the localized trajectory. This must be taken under consideration when planning the space missions. And also the localized trajectories may be useful when spaceship flies around the collinear libration point.

Gauss Equations for Local Action-Angle Orbital Elements in Cislunar Space

To track orbits in cislunar space, predict where they will naturally move over time, and identify where unbounded trajectories come from, one may consider local action-angle orbital elements—coordinates that relate a spacecraft state to specific trajectories and exist in approximately integrable regions of the Earth–moon circular restricted three-body problem (CR3BP). As local action-angle elements are a semi-analytical analog to two-body orbital elements, the theory is extended to allow for the study of arbitrary perturbations to the dynamics. Namely, we derive Gauss equations for an arbitrary perturbing acceleration—continuous or discrete—to the CR3BP. Examples for continuous thrust and impulsive ΔV are provided in cislunar space, i.e., around Earth–moon L1,2 in the CR3BP. Strategies for instantaneous maneuver design and transfers between quasi-periodic orbits and manifolds are developed.

Delivery of DART Impact Ejecta to Mars and Earth: Opportunity for Meteor Observations

NASA’s Double Asteroid Redirection Test (DART) and ESA’s Hera missions offer a unique opportunity to investigate the delivery of impact ejecta to other celestial bodies. We performed ejecta dynamical simulations using 3 million particles categorized into three size populations (10 cm, 0.5 cm, and 30 μm) and constrained by early postimpact LICIACube observations. The main simulation explored ejecta velocities ranging from 1 to 1000 m s−1, while a secondary simulation focused on faster ejecta with velocities from 1 to 2 km s−1. We identified DART ejecta orbits compatible with the delivery of meteor-producing particles to Mars and Earth. Our results indicate the possibility of ejecta reaching the Mars Hill sphere in 13 yr for launch velocities around 450 m s−1, which is within the observed range. Some ejecta particles launched at 770 m s−1 could reach Mars's vicinity in 7 yr. Faster ejecta resulted in a higher flux delivery toward Mars and particles impacting the Earth Hill sphere above 1.5 km s−1. The delivery process is slightly sensitive to the initial observed cone range and driven by synodic periods. The launch locations for material delivery to Mars were predominantly north of the DART impact site, while they displayed a southwestern tendency for the Earth–Moon system. Larger particles exhibit a marginally greater likelihood of reaching Mars, while smaller particles favor delivery to Earth–Moon, although this effect is insignificant. To support observational campaigns for DART-created meteors, we provide comprehensive information on the encounter characteristics (orbital elements and radiants) and quantify the orbital decoherence degree of the released meteoroids.

Forming Massive Terrestrial Satellites through Binary-exchange Capture

The number of planetary satellites around solid objects in the inner solar system is small either because they are difficult or unlikely to form or because they do not survive for astronomical timescales. Here we conduct a pilot study on the possibility of satellite capture from the process of collision-less binary exchange and show that massive satellites in the range 0.01–0.1 M ⊕ can be captured by Earth-sized terrestrial planets in a way already demonstrated for larger planets in the solar system and possibly beyond. In this process, one of the binary objects is ejected, leaving the other object as a satellite in orbit around the planet. We specifically consider satellite capture by an “Earth” in an assortment of hypothetical encounters with large terrestrial binaries at 1 au around the Sun. In addition, we examine the tidal evolution of captured objects and show that orbit circularization and long-term stability are possible for cases resembling the Earth–Moon system.

Analysis of the Reasons Why the Moon Formed Earlier than the Earth

After the birth of the sun, planets and satellites formed. Since the mass of the moon is much smaller than that of the Earth, the heat exchange rate of the moon will be faster than that of the Earth. Therefore, the lunar nebula will complete the condensation process faster than the formation of the Earth.

A computational study of the role of cobalt in thiophene adsorption on small Mo and MoCo clusters as site models for the HDS process

Non periodic density functional theory calculations are used to investigate the role of cobalt atoms in the adsorption of thiophene on small Mo and MoCo clusters. Metallic aggregates play the role of those active sites found in the true catalysts. Two interaction modes between thiophene and metallic sites are considered, namely, the S-mode, in which the organosulfur molecule interacts through the S atom, and the R-mode, in which the interaction takes place through the thiophene ring. A large number of sites, in which thiophene effectively adsorbs, was found, both in the monometallic case and in the bimetallic one. Considerably larger adsorption energies were found when thiophene interacts via the R-mode than when adsorption occurs through the S-mode. The activation of C-S bonds is also more important for R-mode cases than for S-mode ones. Further analysis made on some selected systems and based on density of states and molecular orbital overlap population-projected density of states reveals that thiophene and metallic clusters interact in an energy range around −6.0 eV with respect to the Fermi energy. Bands observed at energies below −6.0 eV correspond to thiophene states that become shifted with respect to the values obtained for isolated thiophene depending on the strength of the interaction. Bands above -6.0 eV describe how C and S atoms interact with Co and Mo ones, providing both bonding and antibonding patterns that helps to understand the overall interaction. Most important is the finding that cobalt atoms seem to play no relevant role during the adsorption of thiophene on metallic sites. Thus, present results obtained using non periodic GGA density functional theory seem to point to cobalt taking part in another step of the overall HDS process, hydrogen adsorption or hydrogen attack to C-S bonds, for instance.

A Relativistic Framework to Estimate Clock Rates on the Moon

As humanity aspires to explore the solar system and investigate distant worlds such as the Moon, Mars, and beyond, there is a growing need to estimate and model the rate of clocks on these celestial bodies and compare them with the rate of standard clocks on Earth. According to Einstein’s theory of relativity, the rate of a standard clock is influenced by the gravitational potential at its location and its relative motion. A convenient choice of local reference frames allows for the comparison of local time variations of clocks due to gravitational and kinematic effects. We estimate the rate of clocks on the Moon using a locally freely falling reference frame coincident with the center of mass of the Earth–Moon system. A clock near the Moon’s selenoid ticks faster than one near the Earth’s geoid, accumulating an extra 56.02 μs day−1 over the duration of a lunar orbit. This formalism is then used to compute the clock rates at Earth–Moon Lagrange points. Accurate estimation of the rate differences of coordinate times across celestial bodies and their intercomparisons using clocks on board orbiters at Lagrange points as time transfer links is crucial for establishing reliable communications infrastructure. This understanding also underpins precise navigation in cislunar space and on celestial bodies’ surfaces, thus playing a pivotal role in ensuring the interoperability of various position, navigation, and timing systems spanning from Earth to the Moon and to the farthest regions of the inner solar system.

Low-energy Earth–Moon transfer autonomous guidance considering high-fidelity orbital dynamics

Low-energy Earth–Moon transfer autonomous guidance considering high-fidelity orbital dynamics

Geological evidence reveals a staircase pattern in Earth’s rotational deceleration evolution

The Earth’s rotation has been decelerating throughout its history due to tidal dissipation, but the variation of the rate of this deceleration through time has not been established. We present a detailed analysis of eight geological datasets to constrain the Earth’s rotational history from 650 to 240 Mya. The results allow us to test physical tidal models and point to a staircase pattern in the Earth’s deceleration from 650 to 280 Mya. During this time interval, the Earth–Moon distance increased by approximately 20,000 km and the length of day increased by approximately 2.2 h. Specifically, there are two intervals with high Earth rotation deceleration, 650 to 500 Mya and 350 to 280 Mya, separated by an interval of stalled deceleration from 500 to 350 Mya. The interval with stalled deceleration is attributed mainly to reduced tidal dissipation due to the continent-ocean configuration at the time, not to changes in Earth’s dynamical ellipticity from continental assembly or glaciation. Modeling indicates that, except for the very recent time, tidal dissipation is the main driver for decelerating Earth rotation. One potential implication of our findings is that the Earth’s tidal dissipation, along with Earth’s rotation deceleration, may play a role in the evolving Earth.

Polar Orbits around the Newly Formed Earth–Moon Binary System

We examine the dynamics and stability of circumbinary particles orbiting around the Earth–Moon binary system. The moon formed close to the Earth (semimajor axis a EM ≈ 3 R ⊕) and expanded through tides to its current day semimajor axis (a EM = 60 R ⊕). Circumbinary orbits that are polar or highly inclined to the Earth–Moon orbit are subject to two competing effects: (i) nodal precession about the Earth–Moon eccentricity vector and (ii) Kozai–Lidov oscillations of eccentricity and inclination driven by the Sun. While we find that there are no stable polar orbits around the Earth–Moon orbit with the current day semimajor axis, polar orbits were stable immediately after the formation of the Moon, at the time when there was a lot of debris around the system, up to when the semimajor axis reached about a EM ≈ 10 R ⊕. We discuss implications of polar orbits on the evolution of the Earth–Moon system and the possibility of polar orbiting moons around exoplanet–moon binaries.

Spectro-photometry of Phobos simulants: I. Detectability of hydrated minerals and organic bands

Previous Mars Reconnaissance Orbiter and Mars Express observations of Phobos and Deimos, the moons of Mars, have improved our understanding of these small bodies. However, their formation and composition remain poorly constrained. Physical and spectral properties suggest that Phobos may be a weakly thermal-altered captured asteroid but the dynamical properties of the martian system suggest a formation by giant collision similar to the Earth moon. In 2027, the JAXA’s MMX mission aims to address these outstanding questions.We undertook measurements with a new simulant called OPPS (Observatory of Paris Phobos Simulant) which closely matches Phobos reflectance spectra from the visible to the mid-infrared wavelength range. The simulant was synthesized using a mixture of olivine, saponite, anthracite, and coal.Since observation geometry strongly influences the photometry and spectra of the light reflected from planetary surfaces, we evaluated the parameters obtained by modeling the phase curves – obtained through laboratory measurements – of two different Phobos simulants (UTPS-TB and OPPS) using Hapke IMSA model. Our results show that the photometric properties of Phobos simulants are not fully consistent with those of carbonaceous chondrites and martian meteorites. We also investigated the detection of volatiles/organic compounds and hydrated minerals, as the presence of such components is expected on Phobos in the hypothesis of a captured primitive asteroid. To investigate their detectability, we examined the variability of the 3.28μm and 3.42μm absorption bands related to aliphatic/aromatic carbon (as a proxy of organic material), as well as the 2.7μm O–H feature in a Phobos laboratory spectroscopic simulant. The results indicate that a significant amount of organic compounds is required for the detection of C–H bands at 3.4μm. The bands at 3.28 and 3.42μm are faint (less than 2%) when ∼3 wt% of organic compounds are present in the simulant and are likely undetectable by the MIRS spectrometer onboard the MMX mission. When the concentration of aliphatic and aromatic compounds is increased to 6 wt%, a positive detection starts to become more plausible using remote sensing infrared spectroscopy. In contrast, the 2.7μm absorption band, due to hydrated minerals, is much deeper and easier to detect than C–H organic features at the same concentration levels. The feature is still clearly detectable even when the simulant contains only 3 vol.% of phyllosilicates, corresponding to 0.7 wt% OH groups.Posing limits on detectability of some possible key components of Phobos surface will be pivotal to prepare and interpret future observations of the MIRS spectrometer as well as TENGOO and OROCHI cameras onboard MMX mission.

Design of Entire-Flight Pinpoint Return Trajectory for Lunar DRO via Deep Neural Network

Lunar DRO pinpoint return is the final stage of manned deep space exploration via a lunar DRO station. A re-entry capsule suffers from complicated dynamic and thermal effects during an entire flight. The optimization of the lunar DRO return trajectory exhibits strong non-linearity. To obtain a global optimal return trajectory, an entire-flight lunar DRO pinpoint return model including a Moon–Earth transfer stage and an Earth atmosphere re-entry stage is constructed. A re-entry point on the atmosphere boundary is introduced to connect these two stages. Then, an entire-flight global optimization framework for lunar DRO pinpoint return is developed. The design of the entire-flight return trajectory is simplified as the optimization of the re-entry point. Moreover, to further improve the design efficiency, a rapid landing point prediction method for the Earth re-entry is developed based on a deep neural network. This predicting network maps the re-entry point in the atmosphere and the landing point on Earth with respect to optimal control re-entry trajectories. Numerical simulations validate the optimization accuracy and efficiency of the proposed methods. The entire-flight return trajectory achieves a high accuracy of the landing point and low fuel consumption.

Dynamics around the Earth–Moon triangular points in the Hill restricted 4-body problem

This paper investigates the motion of a small particle moving near the triangular points of the Earth–Moon system. The dynamics are modeled in the Hill restricted 4-body problem (HR4BP), which includes the effect of the Earth and Moon as in the circular restricted 3-body problem (CR3BP), as well as the direct and indirect effect of the Sun as a periodic time-dependent perturbation of the CR3BP. Due to the periodic perturbation, the triangular points of the CR3BP are no longer equilibrium solutions; rather, the triangular points are replaced by periodic orbits with the same period as the perturbation. Additionally, there is a 2:1 resonant periodic orbit that persists from the CR3BP into the HR4BP. In this work, we investigate the dynamics around these invariant objects by performing a center manifold reduction and computing families of 2-dimensional invariant tori and their linear normal behavior. We identify bifurcations and relationships between families. Mechanisms for transport between the Earth, L4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$L_4$$\\end{document}, and the Moon are discussed. Comparisons are made between the results presented here and in the bicircular problem (BCP).

Low-Energy Transfers to Lunar Distant Retrograde Orbits from Geostationary Transfer Orbits

This study focuses on the low-energy transfers to lunar distant retrograde orbits (DROs) from geostationary transfer orbits (GTOs) in the bicircular-restricted sun–Earth–moon four-body problem. The low-energy transfer is essential for low-cost small satellites reaching out to the Moon, and the departure from GTO allows more rideshare opportunities. We first created several large-scale databases of trajectory segments, such as GTO to apogee in the weak-stability area, apogee to perilune, and DRO to perilune. Then, millions of GTO–DRO transfer trajectories with double powered lunar flybys (PLFs) and weak stability boundary (WSB) ballistic transfer were constructed through trajectory patching. The key flight information, such as the ΔV–time-of-flight Pareto fronts, launch windows, and the flight mode via WSB ballistic transfer, is obtained from feasible solutions. Results show that low-energy GTO–DRO transfers can be achieved by exploiting PLFs and WSB ballistic arcs, which suggests potential applications in the cislunar space.

Exomoons and Exorings with the Habitable Worlds Observatory. I. On the Detection of Earth–Moon Analog Shadows and Eclipses

The highest priority recommendation of the Astro2020 Decadal Survey for space-based astronomy was the construction of an observatory capable of characterizing habitable worlds. In this paper series we explore the detectability of and interference from exomoons and exorings serendipitously observed with the proposed Habitable Worlds Observatory (HWO) as it seeks to characterize exoplanets, starting in this manuscript with Earth–Moon analog mutual events. Unlike transits, which only occur in systems viewed near edge-on, shadow (i.e., solar eclipse) and lunar eclipse mutual events occur in almost every star–planet–moon system. The cadence of these events can vary widely from ∼yearly to multiple events per day, as was the case in our younger Earth–Moon system. Leveraging previous space-based (EPOXI) light curves of a Moon transit and performance predictions from the LUVOIR-B concept, we derive the detectability of Moon analogs with HWO. We determine that Earth–Moon analogs are detectable with observation of ∼2–20 mutual events for systems within 10 pc, and larger moons should remain detectable out to 20 pc. We explore the extent to which exomoon mutual events can mimic planet features and weather. We find that HWO wavelength coverage in the near-infrared, specifically in the 1.4 μm water band where large moons can outshine their host planet, will aid in differentiating exomoon signals from exoplanet variability. Finally, we predict that exomoons formed through collision processes akin to our Moon are more likely to be detected in younger systems, where shorter orbital periods and favorable geometry enhance the probability and frequency of mutual events.

Navigation performance analysis of Earth–Moon spacecraft using GNSS, INS, and star tracker

Global Navigation Satellite System (GNSS) can provide an approach for spacecraft autonomous navigation in earth–moon space to make up for the insufficiency of earth-based tracking, telemetry, and control systems. However, its weak power and poor observation geometry near the moon causes new problems. After the GNSS signal characteristics and satellite visibility were evaluated in Phasing Orbit and Lunar Transfer Orbit, we proposed an adaptive Kalman filter based on the Carrier-to-Noise ratio (C/N0) and innovation vector to weaken the influence of GNSS accuracy attenuation as much as possible. The experimental results show that the spacecraft position and velocity accuracy are better than 10 m and 0.1 m/s near the Earth, and better than 50 m and approximately 0.2 m/s near the moon use GNSS with the proposed adaptive algorithms. Additionally, because of the deterioration of navigation performance based on the orbit filter during orbital maneuvering, we used accelerometer data to compensate for the dynamic model to maintain navigation performance. The results of the experiment provide a reference for subsequent studies.

Lessons Learned in Designing a Proposed Ultraviolet Sterilization System for Space

This paper presents a number of lessons learned while designing a proposed sterilization system for Mars Sample Return. This sterilization system is needed to inactivate any potentially hazardous Mars material on the exterior surface of the vessel containing sealed sample tubes filled with Mars rock cores, regolith and atmosphere. These returned samples would provide information on the geologic history of Mars, the evolution of its climate and the potential for ancient life. Mars Sample Return is categorized at Planetary Protection Category V Restricted Earth Return, so it is required to protect the Earth–Moon system from the biological impact of returning samples from Mars to Earth. This article reviews lessons learned in the development of a particular engineering implementation to support the protection of the Earth–Moon biosphere: the use of in situ ultraviolet LED illumination. The details of the biological efficacy of this approach or the policy-related impacts are outside of the scope of this manuscript. The lessons learned presented here include establishing design requirements for the system, the selection of a light source, optical design options, contamination control and approaches to thermal and power management.