Planet Mercury Research Articles

Zero-g positioning for the BepiColombo ISA accelerometer

BepiColombo is a joint ESA/JAXA mission devoted to study the planet Mercury through two orbiters (MPO and MMO) to be launched in 2017. Among the main objectives, the European MPO aims at measuring the gravitational field of Mercury with unprecedented accuracy, through a careful reconstruction of the spacecraft orbit. The use of a very high sensitive tri-axial accelerometer, named ISA, will improve the orbital determination through an accurate sensing of the non-gravitational accelerations experienced by the spacecraft, mainly due to the solar radiation.The development of the three accelerometers, aluminium-made and constituted by electro-mechanical transducers, faced different issues to reach the required performance.One of the most relevant topic was the zero-g positioning, i.e. the measure of the sensing mass rest position when the sensor is in free-fall conditions (named briefly zero-g), condition that would be observed in orbit. The sensor offers the best performance when the sensing mass operates around this equilibrium position. Therefore this position needs to be identified and the mass has to be located there to guarantee the requirements imposed by the measurement of the non-gravitational accelerations. The group of Experimental Gravitation at IAPS/INAF in Rome developed an experimental procedure and a set-up to measure the zero-g position, carrying out a measurement campaign. This procedure will be applied to measure the zero-g positioning of ISA flight models.

Cosmochemical and spectroscopic properties of Northwest Africa 7325—A consortium study

AbstractThis work is part of a project to build an infrared database in order to link IR data of planetary materials (and therefore possible Mercury material) with remote sensing observations of Mercury, which will probably be obtained by the MERTIS instrument on the forthcoming BepiColombo mission.The unique achondrite Northwest Africa (NWA) 7325, which has previously been suggested to represent the first sample from Mercury, was investigated by optical and electron microscopy, and infrared and Raman spectroscopy. In addition, the oxygen, strontium, xenon, and argon isotopes were measured and the abundance of selected trace elements determined. The meteorite is a cumulate rock with subchondritic abundances of HFSE and REE and elevated Sr contents, which underwent a second heating and partial remelting process. Oxygen isotope measurements show that NWA 7325 plots in the ureilite field, close to the ALM‐A trachyandesitic fragment found in the unique Almahata Sitta meteorite breccia. On the other hand, mineralogical investigations of the pyroxenes in NWA 7325 provide evidence for similarities to the lodranites and acapulcoites. Furthermore, the rock is weakly shocked and argon isotope data record ancient (~4.5 Ga) plateau ages that have not been reset. The sample records a cosmogenic exposure age of ~19 Ma. Systematics of Rb‐Sr indicate an extreme early volatile depletion of the precursor material, similar to many other achondrite groups. However, despite its compositional similarities to other meteorite groups, our results suggest that this meteorite is unique and unrelated to any other known achondrite group. An origin for NWA 7325 as a sample from the planet Mercury is not supported by the results of our investigation. In particular, the evidence from infrared spectroscopy indicates that a direct relationship between NWA 7325 and the planet Mercury can be ruled out: no acceptable spectral match between laboratory analyses and remote sensing observations from Mercury has been obtained. However, we demonstrate that infrared spectroscopy is a rapid and nondestructive method to characterize mineral phases and thus an excellent tool for planetary surface characterization in space missions.

The interior configuration of planet Mercury constrained by moment of inertia and planetary contraction

This paper presents an analysis of present-day interior configuration models for Mercury considering cores of Fe-S or Fe-Si alloy, the latter possibly covered by a solid FeS layer, in light of the improved limit of planetary contraction of 7 km derived from MErcury Surface, Space ENvironment, GEochemistry, and Ranging observations of surface landforms. Density profiles, generated by a Monte Carlo approach, are constrained by Mercury's mass, polar moment of inertia (C), fraction of polar moment corresponding to its outer solid shell (Cm/C), and observed planetary contraction. Results show that the outer liquid core boundary is constrained to 1985–2090 km in radius, where large radii correspond to high Si and S core contents and high mantle densities or the presence of an FeS layer at the top of the outer core. The bulk core S and Si contents are within 2.8–8.9 wt % and above 8.5 wt %, respectively, where an increase of light element core content correlates positively with mantle density and core size. The size of the inner core is constrained by the observed planetary contraction to below 1454 or 1543 km in radius for bulk cores rich in S (near 8.9 wt %) or Si (near 25 wt %), respectively. For cores poor in light elements, inner cores up to 1690 km in radius remain consistent with the observed planetary contraction. Finally, we show that solid FeS at outer core conditions, previously argued to float on liquid Fe-S, may be denser than the residual liquid. This implies that a separate mechanism may be required to maintain an FeS layer at the suggested location.

Asymmetries in the dust flux at Mercury

The planet Mercury has an extended and tenuous exosphere made up of atoms that are ejected from the surface by energetic processes, including hypervelocity micrometeoritic impacts, photon-stimulated desorption by UV radiation, and ion sputtering. Meteoroid impacts of particles smaller than 1cm, which are important for replenishing the exosphere daily, are not well-studied. We present a systematic investigation of spatial asymmetries in the impactor rate of micrometeoroids over Mercury’s surface as a function of planetary true anomaly (TAA). Since the orbit of Mercury is quite eccentric a seasonal variation of the impact rate is to be expected. We find that the source peaks near the planetary equator for most TAA. Contrary to previous assumptions, we find the source to be non-uniform in local time. Only certain regions of Mercury are exposed to dust as a result of the orbital elements of Mercury and of the Main Belt particles (inclination less than 20°). Our results offer important constraints on transport models used for interpreting measurements of this exosphere, but also inform studies of space weathering of Mercury’s surface.

First MESSENGER orbital observations of Mercury's librations

AbstractWe have coregistered laser altimeter profiles from 3 years of MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) orbital observations with stereo digital terrain models to infer the rotation parameters for the planet Mercury. In particular, we provide the first observations of Mercury's librations from orbit. We have also confirmed available estimates for the orientation of the spin axis and the mean rotation rate of the planet. We find a large libration amplitude of 38.9 ± 1.3 arc sec and an obliquity of the spin axis of 2.029 ± 0.085 arc min, results confirming that Mercury possesses a liquid outer core. The mean rotation rate is observed to be (6.13851804 ± 9.4 × 10−7)°/d (a spin period of 58.6460768 days ± 0.78 s), significantly higher than the expected resonant rotation rate. As a possible explanation we suggest that Mercury is undergoing long‐period librational motion, related to planetary perturbations of its orbit.

Alchemy and the Transgendering of Mercury

Within late medieval alchemical texts, Latin authors adopted both classical and Arabic concepts of physical matter. They assumed that metals were composed of two polarized substances – hot, dry and masculine Philosophic Sulphur, and cool, wet and feminine Philosophic Mercury – whose ‘Chemical Wedding’ within the laboratory produced the Philosophers’ Stone. As visual illustrations developed in alchemical manuscripts and early printed books from the late fourteenth century onward, artists represented these substances with a variety of male and female characters, with Philosophic Mercury almost always depicted as a woman. At the same time, the planet Mercury, which oversaw the ripening of the metal Quicksilver within the earth, also played an important role within alchemical illustrations. This paper will examine how artists navigated this confusion by examining gendered images of the philosophical concept Mercury, the metal Mercury, and the planet Mercury, in light of shifting attitudes towards women in early modern science.

Reference surfaces of the planet Mercury from MESSENGER

The aim of this work is to study the reference surfaces of the planet Mercury obtained by the MESSENGER mission in order to provide a geodetic reference system (GRS) for the planet. The reference surfaces under consideration are the geoid and the reference ellipsoid. The reference ellipsoid is a triaxial planetocentric equipotential ellipsoid that best fits the geoid. To determine the reference surfaces, two methods are presented. In this line, the shape of the planet is sampled by expanding the global shape model (GSM) GTMES_125V03_SHA only up to the degree strength of the global gravity model (GGM) GGMES_50V06_SHA. The spatial resolution of the sampling points is selected based on the degree strength and the latitude of the location. According to our preferred method, we estimate the values for the semi-major equatorial axis, semi-minor equatorial axis, and polar axis of the reference ellipsoid equal to 2,439,422±368m, 2,439,304±368m, and 2,439,178±368m, respectively. Moreover, we estimate the geoid potential value equal to 9,032,044±1361m2/s2. The three axes of the reference ellipsoid give the polar and equatorial flattenings equal to (100±213)×10-6 and (48±213)×10-6, respectively. However, we show that the best-fitting ellipsoid gives the polar and equatorial flattenings equal to (896±213)×10-6 and (426±213)×10-6, respectively. The best-fitting ellipsoid is a triaxial ellipsoid that fits the shape of Mercury in a least-squares sense. The significant discrepancy observed between the flattenings of the two ellipsoids is a consequence of Mercury’s geophysical characteristics together with its non-hydrostatic equilibrium. The results provided in the present work prove adequate for defining a promised GRS for the planet Mercury.

Inside the Chönyid Bardo: Winner of the 2015 AWP Intro Journals Project in Nonfiction, selected by Sue William Silverman

Inside the Chönyid BardoWinner of the 2015 AWP Intro Journals Project in Nonfiction, selected by Sue William Silverman Jan Becker (bio) It took us four days to discover that our service provider had switched our phone number without telling us. In those four days, we became accustomed to the absence of a ringing phone. I was too busy getting ready for a trip to Cassadaga, a Spiritualist camp in central Florida, to notice how quiet it had become. The only calls we received during those four days were from telemarketers. This should have signaled something was amiss, because our landline is on the Do-Not-Call registry. Then on the fourth day, Matt, my boyfriend, called a friend, who asked him why we’d changed our number and why we hadn’t bothered to tell him. It is easy to lay blame somewhere in a situation like this, and I rested it solely on the planet Mercury. It was in the middle of a retrograde pattern, where the orbit appears to move backward through the night sky. According to astrologers, when Mercury’s orbit goes retrograde, communications break down, computers are hacked or crash with increasing frequency, contracts are broken, reliable people suddenly become unreliable, and the results can be chaotic. This mistake could be blamed on a new customer service agent who mistakenly hit the wrong button and canceled our phone service, but better to say it was a contortion of a planet millions of miles away—better to say it was the winged god playing a capricious game. Panicked, the agent realized his mistake and switched us back on, but under a different telephone number. He might have been worried about his new job and told no one that the only string in the tin can that connected us to the rest of the world had been severed. The first call I made when we got our new phone number (from a different, apologetic agent) was to a close friend, Michael, who’d been in for outpatient surgery. “How did you know I was trying to reach you?” he asked. “I didn’t,” I answered. “I just wanted to know how the surgery went.” [End Page 92] “Robbie died last night.” Robbie, Michael’s best friend, my friend, Matt’s friend, Eagle Scout, husband. Dead. In the four days without our familiar phone number, we missed our last chance to talk with Rob, who’d been battling liver cancer for the last year. Years earlier, during a period of major depression, I’d broken a newly blossoming clematis vine in the garden I was planting in Michael’s yard. When the vine snapped in my hands, I cried harder than I’d ever cried before. I thought I had killed the whole plant. I sobbed so hard I felt something snap inside with a loud crack, like a tree giving in to the lumberjack’s saw and falling, hard. I could feel a strange new pain, like poison smog escaping my body. It baffled me and made me wonder if I was being touched by something divine. Robbie was certified in massage therapy and had mentioned that emotions are stored in the memory of our muscles, so I asked him, “What does this mean?” “It’s nothing God handed you,” he said. “It’s just part of you getting your shit together.” O ye Buddhas and Bodhisattvas, abiding in the Ten Directions, endowed with great compassion, endowed with foreknowledge, endowed with the divine eye, endowed with love, affording protection to sentient beings, consent through the power of your great compassion to come hither…. (Invocation to the Buddhas and Bodhisattvas, appendix to The Tibetan Book of the Dead) I’m not a Buddhist. I’m probably not anything, but I call myself a pantheist. I decided a long time ago that I would believe in everything because I would hate to miss Heaven due to a technicality. While I am not Buddhist, when someone close to me dies I reach for my Tibetan Book of the Dead, in case my loved one might be lost and alone inside the chönyid bardo. The chönyid bardo is...

Precession of a Planet with the Multiple Scales Lindstedt–Poincare Technique

Abstract The recently developed multiple scales Lindstedt–Poincare (MSLP) technique is successfully applied to a mathematical model of planet motion. The equation is originally developed to precisely understand the orbital motion of the planet Mercury around the Sun and the precession of the orbit due to the relativistic effects. The quadratic nonlinear equation is solved by the classical Lindstedt–Poincare method (LP) and then by the newly developed multiple scales Lindstedt–Poincare method (MSLP). Both approximate solutions are contrasted with the numerical simulations. When the relativistic effects are small, all three solutions coincide with each other. When the perturbation effects are increased, the MSLP solutions agree better with the numerical solutions than the LP solutions. The precession of the perihelion of the planet is calculated and compared for the approximate solutions.

The pre-flight calibration setup of the instrument SIMBIO-SYS onboard the mission BepiColombo

BepiColombo, an European Space Agency (ESA) mission being conducted in cooperation with the Japan space agency, will explore Mercury with a set of eleven instruments onboard the spacecraft Mercury Planetary Orbiter (MPO). Among them, SIMBIO-SYS (Spectrometers and Imagers for MPO BepiColombo Integrated Observatory SYStem) is a complex instrument that will provide images and spectra in the 400–2000nm wavelength range of the entire surface of Mercury. Pre-flight calibration of the SYMBIO-SYS instrument is mandatory for reliable scientific interpretation of images and spectra returned from the planet Mercury. This paper presents the calibration device designed and implemented for the specific requirements of this instrument. It mainly consists of a thermal vacuum chamber simulating the space environment, an optical bench collecting calibration sources and optical elements that simulate the conditions of Mercury observations, mechanical interfaces used for positioning the three channels inside the vacuum chamber, thermal interfaces to explore the operating temperatures, computer interfaces that allow to communicate with both the instrument and the calibration elements and synchronize the calibrations sequences with the status of the calibration device. As the major goal is the characterization of the radiometric performances of the three channels of SIMBIO-SYS, radiometric performances of the test setup evaluated by simulations and measurements are emphasized.

Einstein's perihelion formula and its generalization

Einstein's perihelion advance formula can be given a geometric interpretation in terms of the curvature of the ellipse. The formula can be obtained by splitting the constant term of an auxiliary polar equation for an elliptical orbit into two parts that, when combined, lead to the expression of this relativistic effect. Using this idea, we develop a general method for dealing with orbital precession in the presence of central perturbing forces, and apply the method to the determination of the total (relativistic plus Newtonian) secular perihelion advance of the planet Mercury.

Extreme Ultraviolet Radiation Measurement for Planetary Atmospheres/Magnetospheres from the Earth-Orbiting Spacecraft (Extreme Ultraviolet Spectroscope for Exospheric Dynamics: EXCEED)

The Sprint-A satellite with the EUV spectrometer (Extreme Ultraviolet Spectroscope for Exospheric Dynamics: EXCEED) was launched in September 2013 by the Epsilon rocket. Now it is orbiting around the Earth (954.05 km×1156.87 km orbit; the period is 104 minutes) and one has started a broad and varied observation program. With an effective area of more than 1 cm2 and well-calibrated sensitivity in space, the EUV spectrometer will produce spectral images (520–1480 Å) of the atmospheres/magnetospheres of several planets (Mercury, Venus, Mars, Jupiter, and Saturn) from the Earth’s orbit. At the first day of the observation, EUV emissions from the Io plasma torus (mainly sulfur ions) and aurora (H2 Lyman and Werner bands) of Jupiter have been identified. Continuous 3-month measurement for Io’s plasma torus and aurora is planned to witness the sporadic and sudden brightening events occurring on one or both regions. For Venus, the Fourth Positive (A1 Π-X1 Σ +) system of CO and some yet known emissions of the atmosphere were identified even though the exposure was short (8-min). Long-term exposure from April to June (for approximately 2 months) will visualize the Venusian ionosphere and tail in the EUV spectral range. Saturn and Mars are the next targets.

Magnetic reconnection at the edge of Uranus's magnetic field

A new modeling study sheds light on how the magnetosphere of Uranus compares to those of other planets. Magnetospheres around the inner planets Mercury and Earth are primarily driven by the solar wind—the charged particles spewed out from the Sun—through magnetic reconnection, in which the planet's magnetic field lines break and reconnect, releasing energy in the process.

Classic tests of General Relativity described by brane-based spherically symmetric solutions

We discuss a way to obtain information about higher dimensions from observations by studying a brane-based spherically symmetric solution. The three classic tests of General Relativity are analyzed in details: the perihelion shift of the planet Mercury, the deflection of light by the Sun, and the gravitational redshift of atomic spectral lines. The braneworld version of these tests exhibits an additional parameter $b$ related to the fifth-coordinate. This constant $b$ can be constrained by comparison with observational data for massive and massless particles.

Effect of GUP on the Kepler problem and a variable minimal length

Various approaches to quantum gravity, such as string theory, predict a minimal measurable length and a modification of the Heisenberg uncertainty principle near the Plank scale, known as the generalized uncertainty principle (GUP). Here we study the effects of GUP, which preserves the rotational symmetry of the space–time, on the Kepler problem. By comparing the value of the perihelion shift of the planet Mercury in Schwarzschild – de Sitter space–time with the resultant value of GUP, we find a relation between the minimal measurable length and the cosmological constant of the space–time. Now, if the cosmological constant varies with time, we have a variable minimal length in the space–time. Finally, we investigate the effects of GUP on the stability of circular orbits.

Astrology as a Social Framework

During the Early Modern period, many believed that the seven planets—Mercury, Venus, Mars, Jupiter, Saturn, the sun, and the moon—affected the course of terrestrial events and determined the temperament, complexion, profession, and even the manner of death of individuals. Such concepts were depicted by artists in a series of images commonly referred to as the ‘Children of the Planets’. By merging scientific knowledge and popular imagery, the convention helped to shape the contemporary understanding of the cosmos. Astrology is often described in terms of the correspondence between the macrocosm and the microcosm or the universe and the individual, but by linking diverse individuals according to mutual planetary affiliations, the ‘Children of the Planets’ also offered a system for categorizing corporate identity and defining social relations.

Secular perihelion advances of the inner planets and asteroid Icarus

A small effect expected from a recently proposed gravitational impact model (Wilhelm et al., 2013) is used to explain the remaining secular perihelion advance rates of the planets Mercury, Venus, Earth, Mars, and the asteroid (1566) Icarus—after taking into account the disturbances related to Newton’s Theory of Gravity. Such a rate was discovered by Le Verrier (1859) for Mercury and calculated by Einstein (1915, 1916) in the framework of his General Theory of Relativity (GTR). Accurate observations are now available for the inner Solar System objects with different orbital parameters. This is important, because it allowed us to demonstrate that the quantitative amount of the deviation from an 1/r potential is—under certain conditions—only dependent on the specific mass distribution of the Sun and not on the characteristics of the orbiting objects and their orbits. A displacement of the effective gravitational from the geometric centre of the Sun by about 4400m towards each object is consistent with the observations and explains the secular perihelion advance rates.

Analyzing Black Hole Super-Radiance Emission of Particles/Energy from a Black Hole as a Gedankenexperiment to Get Bounds on the Mass of a Graviton

Use of super-radiance in BH physics, sodE/dt<0specifies conditions for a mass of a graviton being less than or equal to 1065grams, allows for determing what role additional dimensions may play in removing the datum that massive gravitons lead to 3/4th the bending of light past the planet Mercury. The present document makes a given differentiation between super-radiance in the case of conventional BHs and Braneworld BH super-radiance, which may delineate whether Braneworlds contribute to an admissible massive graviton in terms of removing the usual problem of the 3/4th the bending of light past the planet Mercury which is normally associated with massive gravitons. This leads to a fork in the road between two alternatives with the possibility of needing a multiverse containment of BH structure or embracing what Hawkings wrote up recently, namely, a redo of the event horizon hypothesis as we know it.

Djerfisherite: nebular source of refractory potassium

Djerfisherite is an important carrier of potassium in highly reduced enstatite chondrites, where it occurs in sub-round metal-sulfide nodules. These nodules were once free-floating objects in the protoplanetary nebula. Here, we analyze existing and new data to derive an equation of state (EOS) for djerfisherites of \( {\text{K}}_{ 6} ({\text{Cu}},{\text{Fe}},{\text{Ni}})^{B} ({\text{Fe}},{\text{Ni}},{\text{Cu}})_{24}^{C} {\text{S}}_{ 2 6} {\text{Cl}} \) structural formula. We use this EOS to calculate the thermal stability of djerfisherite coexisting in equilibrium with a cooling vapor of solar composition enriched in a dust analogous to anhydrous, chondritic interplanetary dust (C-IDP). We find that condensed mineral assemblages closely match those found in enstatite chondrites, with djerfisherite condensing above 1,000 K in C-IDP dust-enriched systems. Results may have implications for the volatile budgets of terrestrial planets and the incorporation of K into early formed, highly reduced, planetary cores. Previous work links enstatite chondrites to the planet Mercury, where the surface has a terrestrial K/Th ratio, high S/Si ratio, and very low FeO content. Mercury’s accretion history may yield insights into Earth’s.

The extreme ultraviolet spectroscope for planetary science, EXCEED

The extreme ultraviolet spectroscope EXtrem ultraviolet spetrosCope for ExosphEric Dynamics (EXCEED) on board the SPRINT-A mission will be launched in the summer of 2013 by the new Japanese solid propulsion rocket Epsilon as its first attempt, and it will orbit around the Earth with an orbital altitude of around 1000km. EXCEED is dedicated to and optimized for observing the terrestrial planets Mercury, Venus and Mars, as well as Jupiter for several years. The instrument consists of an off axis parabolic entrance mirror, switchable slits with multiple filters and shapes, a toroidal grating, and a photon counting detector, together with a field of view guiding camera. The design goal is to achieve a large effective area but with high spatial and spectral resolution. In this paper, the performance of each optical component will be described as determined from the results of test evaluation of flight models. In addition, the results of the optical calibration of the overall instrument are also shown. As a result, the spectral resolution of EXCEED is found to be 0.3–0.5nm Full Width at Half Maximum (FWHM) over the entire spectral band (52–148nm) and the spatial resolution achieve was 10". The evaluated effective area is around 3cm2. Based on these specifications, the possibility of EXCEED detecting atmospheric ions or atoms around Mercury, Venus, and Mars will be discussed. In addition, we estimate the spectra that might be detected from the Io plasma torus around Jupiter for various hypothetical plasma parameters.