Planetary and Space Science最新文献

The April Lyrid meteor shower is the oldest meteor shower ever recorded continuously throughout history, dating as far back as 687 BC. Before the 20th century, historical sources only provided reports of two years of strong activity and up to nine possible additional events. Currently, the shower has low activity, but it has had significant episodes that, during the 20th century, seem to repeat at time intervals that are multiples of 12yr or 60 yr. Earlier outbursts may have also occurred with a frequency consistent with this period. Outbursts of activity are also known in other meteor showers. The classical explanation that they are correlated to the close proximity of the parent comet to the Earth was proven wrong in the last years of the 20th century and this is also clear in the case of the April Lyrids, whose parent comet is C/1861 G1 (Thatcher), with an orbital period of about 400 yr. Our previous research has led us to compile an additional list of possible April Lyrids in the last 2000 years. This paper has two objectives. First, to present the list of possible Lyrids that we have compiled that would significantly increase the number of historical observations considered to date. Secondly, to study if the historical data fit well with the main theories and recent studies concerning the Lyrids.

In recent decades, the use of optical detection systems for meteor studies has increased dramatically, resulting in huge amounts of data being analyzed. Automated meteor detection tools are essential for studying the continuous meteoroid incoming flux, recovering fresh meteorites, and achieving a better understanding of our Solar System. Concerning meteor detection, distinguishing false positives between meteor and non-meteor images has traditionally been performed by hand, which is significantly time-consuming. To address this issue, we developed a fully automated pipeline that uses Convolutional Neural Networks (CNNs) to classify candidate meteor detections. Our new method is able to detect meteors even in images that contain static elements such as clouds, the Moon, and buildings. To accurately locate the meteor within each frame, we employ the Gradient-weighted Class Activation Mapping (Grad-CAM) technique. This method facilitates the identification of the region of interest by multiplying the activations from the last convolutional layer with the average of the gradients across the feature map of that layer. By combining these findings with the activation map derived from the first convolutional layer, we effectively pinpoint the most probable pixel location of the meteor. We trained and evaluated our model on a large dataset collected by the Spanish Meteor Network (SPMN) and achieved a precision of 98%. Our new methodology presented here has the potential to reduce the workload of meteor scientists and station operators and improve the accuracy of meteor tracking and classification.

We computed the ablation of different spherical artificial meteoroids entering from a low-Earth orbit in the context of the AllBert EinStein mission. AllBert EinStein is intended to reenter spheres of known size and material into the atmosphere to determine the percentage of kinetic energy converted to light. This paper models the reentry to predict magnitude curves for the different initial conditions. An emphasis is placed on determining the difference between the single body ablation model and ESA’s reentry software SCARAB. It is also shown how the CFD simulations can work in synergy with SCARAB results to increase detail in the airflow regime around. Our study shows that with few fixes the meteor method replicates with good accuracy the SCARAB results for different artificial meteoroids, showing the validity of both tools.

PRAIA – Package for the Reduction of Astronomical Images Automatically – is a suite of astrometric and photometric tasks designed to cope with huge amounts of heterogeneous observations with fast processing, no human intervention, minimum parameterization and yet maximum possible accuracy and precision. It is the main tool used to analyse astronomical observations by an international collaboration involving Brazilian, French and Spanish researchers under the Lucky Star umbrella for Solar System studies. In this paper, we focus on the astrometric concepts underneath PRAIA, used in reference system works, natural satellite and NEA astrometry for dynamical and ephemeris studies, and lately for the precise prediction of stellar occultations by planetary satellites, dwarf-planets, TNOs, Centaurs and Trojan asteroids. We highlight novelties developed by us and never reported before in the literature, which significantly enhance astrometry precision and automation. Such as the robust object detection and aperture characterization (BOIA), which explains the long standing empirical photometry/astrometry axiom that recommends using apertures with 2 – 3 $\sigma$ (Gaussian width) radius. We give examples showing the astrometry performance, discuss the advantages of PRAIA over other astrometry packages and comment about future planed astrometry implementations. PRAIA codes and input files are publicly available for the first time at: https://ov.ufrj.br/en/PRAIA/. PRAIA astrometry is useful for Solar System as well as astrophysical observations.

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.