Planetary and Space Science最新文献

The potential commonality of organic synthesis and prebiotic processes on the surface of Titan and primitive Earth makes Saturn's largest moon an indispensable location to seek answers for the origins of life on Earth and elsewhere. NASA's New Frontiers Mission, Dragonfly, is set to arrive on Titan's surface in the mid-2030s. Two of the main scientific goals of the Dragonfly mission are to identify chemical components and potential processes responsible for the production of biologically relevant compounds, and to search for potential biosignatures. To address these mission goals, Dragonfly is equipped with a linear ion trap mass spectrometer, called the Dragonfly Mass Spectrometer, or DraMS. This instrument will measure the molecular composition of Titan's surface at various locations inside and near Selk Crater, where prebiotic chemistry is expected to have occurred. Some molecules of interest on Titan's surface are thought to be sensitive to phase changes within the expected range of the sample handling chain, 94–165 K and 0.04–1.5 bar. A large abundance of such materials may therefore impact the capture efficiency and physical properties of the sampled materials within the DraMS system. In this work, we explore the potential for some of the hypothesized abundant organic molecules to be induced into phase transitions during the end-to-end sampling process by DraMS.

The aim of this paper is to present the concept of a dedicated gravity field mission for the planet Mars, the Mars Quantum Gravity Mission (MaQuIs).

The mission is targeted at improving the data on the gravitational field of Mars, enabling studies on planetary dynamics, seasonal changes, and subsurface water reservoirs.

MaQuIs follows well known mission scenarios, currently deployed for Earth, and includes state-of-the-art quantum technologies to enhance the gained scientific signal.

Micro-computed tomography is a fast and essentially non-destructive technique for studying 3D properties of solid objects. This study explores the use of a micro-CT technique to determine the physical properties and average atomic numbers of 44 chondrules from unequilibrated (petrologic type 3.00 to 3.6) ordinary, carbonaceous, and enstatite chondrites. Many chondrules deviate from a spherical geometry, implying that they were affected by strain during cooling and prior to complete solidification. The porosity of the studied chondrules ranges from 0.04 vol% to 5.3 vol%. Chondrules from carbonaceous chondrites show the highest porosity and the largest voids. The high porosity could be caused by the presence of oxidized precursors in the chondrule melt that escaped as a gas during high temperature processing and crystallization of the melt. In some chondrules, pores are associated with opaque phases, suggesting their formation either during solidification of metal phases and/or during aqueous alteration. The average atomic numbers of chondrules range from 35 ± 4 to 22 ± 2, independently of porosity and opaque content and is likely controlled by the variation of Mg/Fe in chondrule silicates. The absence of a consistent variation between the degree of deformation, chondrule diameter, and porosity among the studied chondrules from different groups, suggests that the processes responsible for the different physical properties of the chondrules are decoupled from each other and are likely universal to all chondrules.

In the absence of Mercurian rocks or meteorites in our collections, komatiites and boninites are often proposed as the best analogue rocks to Mercury lavas. However, despite previous work on the possible analogy between komatiites and Mercury rocks, similar work has not been done for boninites. In this work, we investigate the whole-rock geochemistry and visible/near-infrared (VNIR) spectroscopy of boninitic material collected at three specific areas of the Troodos Massif (Cyprus island). The objective is to evaluate if collected boninites, these along with other boninites present in the literature, can be analogous to Mercury geochemical terranes. On average, we find an unusually high MgO/SiO₂ ratio (0.68) for the boninites from the Troodos Massif compared with previous boninite analysis. This MgO/SiO₂ value is most closely related to the high-Mg regions of Mercury, while the average Al₂O₃/SiO₂ ratio (0.25) is consistent with the Mercurian intermediate terrain and to Mercury's largest pyroclastic deposit. In addition, further affinity to the high-Mg regions and the intermediate terrains of Mercury are shown in regard to Si vs. Mg, Si vs. Ca, and Si vs. Fe content for one sample in particular. We then conduct magmatic modeling on this specific sample to provide a possible parental melt composition for analogue Mercurian magmas. In conclusion, we suggest these specific locations on the Troodos Massif in Cyprus as good geochemical analogue sites for the high-Mg regions of Mercury and explain how boninites could be important benchmark samples for the chemical and spectral data expected from the BepiColombo mission.

Martian rocky material available on Earth has been so far composed of meteorites and is limited in terms of mass and number. This restricted amount directly impairs the possibility to perform destructive analyses and experiments requiring large mass of sample, such as alteration and hydrothermal experiments. One of the main intents of the current Mars Sample Return (MSR) mission is to bring rock samples from Mars to Earth in the next 10 years. While we will have a geological context for the samples, the total mass that will be collected will also be limited. It is thus crucial to seek analogs of martian rocks, not suffering from this limitation while bearing specific martian properties required by the planned experiments.

To overcome this problem in the frame of alteration and hydrothermal experiments, we have built a flexible powder analog system to mimic a typical non-altered shergottite from a chemical and mineralogical perspective. To do so, we have selected the six main mineral phases in weight percentage present in shergottites. For each phase we selected multiple pure terrestrial mineral powders chosen for their chemistry close to their shergottite counterparts. As these mineral phases come from only three different relatively easy access locations, the assemblage is virtually unlimited.

From the Shergottite Analog System (SAS), the Shergottite Sample Powder (SSP)-1 analog has been created to focus on serpentinization and abiotic methane formation experiments under martian conditions. The SAS could also be used to create analogs of Oxia Planum, Gale Crater, or Jezero Crater, and to test possible detection interferences and to determine the sensitivity of multiple analytic techniques by varying the selected phases and their proportions.

Asteroid exploration has allowed detailed observations of boulders on the surface and measurements of craters on the boulders. We focused on the craters near the edges of the boulders and investigated the distance from the impact point to the side surfaces of finite-sized brittle targets when spallation of the side surfaces occurred. First, impact cratering data was compiled, including previous and newly conducted experiments on porous gypsum and less-porous basalt targets. When the distance from the edge to the impact point was shorter than approximately twice the crater radius, spallation of the side surfaces occurred, irrespective of the target material. Then, explosion experiments were conducted using porous gypsum targets to elucidate the physical mechanisms of this process. We investigated the relationship between the distance from the explosion point to the free surface and the incident angle of the stress waves relative to the free surface when spallation occurs. Experimental results suggest that spallation at the side surfaces occurs when the amplitude of the reflected wave caused by a stress wave incident perpendicular to the side surfaces is greater than that at the rim of the crater formed on the top surface. The quantitative relationships obtained in this study using both porous gypsum and less-porous basalt will help to constrain the history of cratered boulders with a wide variety of porosities on asteroids.

Meteor shower identification and search for parent bodies of the meteoroid streams are still on-going topics of meteor science. Both problems are often approached by comparing the orbital (and/or geocentric) parameters of the investigated bodies, as is done in the independent identification method developed by Rudawska et al. (2014). In our work we applied the slightly modified version of the method to 3 most numerous years of the EDMOND (The European viDeo MeteOr Network Database) meteor data, and identified 517 meteor showers. Found showers were characterized and the problematic cases of mis-identification and hyperbolic orbits were analysed. The newly determined mean orbital parameters were then compared with known cometary and NEO (near-Earth object) orbits with the goal to get a broader picture of the associations of known and also suggested parent bodies of the meteoroid streams. From our results, 62 of known associations with the parent bodies were confirmed, and 13 new parent comets were proposed. For 7 meteor showers, new seemingly better solutions among the shower-asteroid associations are suggested.

The term ‘$\alpha$-meteoroid’ was introduced to describe a group of micrometeoroids with certain dynamical properties, which – alongside the group of the $\beta$-meteoroids – had been identified by the first generation of reliable in-situ dust detectors in interplanetary space. In recent years, use of the term $\alpha$-meteoroid has become more frequent again, under a subtly but crucially altered definition. This work shall bring attention to the discrepancy between the term’s original and newly established meaning, and spotlight the now-overlooked group of particles that the term used to describe. We review past and present pertinent literature around the term $\alpha$-meteoroid, and assess the dynamics of the originally referred-to particles with respect to possible sources, showing that their formation is the expected consequence of collisional grinding of the zodiacal cloud at short heliocentric distances. The abundance of the original $\alpha$-meteoroids, which are essentially ‘bound $\beta$-meteoroids’, makes them relevant to all in-situ dust experiments in the inner solar system. Due to the change of the term’s meaning, however, they are not considered by contemporary studies. The characterization of this particle population could elucidate the processing of the innermost zodiacal cloud, and should thus be objective of upcoming in-situ dust experiments. The attained ambiguity of the term $\alpha$-meteoroid is not easily resolved, warranting great care and clarity going forward.

During ESA's Rosetta science mission, the COSIMA instrument collected dust particles in the coma of Comet 67P/Churyumov-Gerasimenko during two years near the comet's nucleus. The largest particles are about $1mm$ in size. The collection process involved a low velocity impact on porous gold-black surfaces, often resulting in breakup, from which information on structural properties has previously been derived (Langevin et al., 2016). However, some of the particles were collected with little damage, but fragmented due to charging during subsequent secondary ion mass spectrometry. This report shows that the details of this electrical fragmentation support the concept of the existence of stable units with sizes of tens of $\mu m$ within the incoming cometary dust particles prior to collection, possibly representing remnants of the early accretion processes.