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Detecting near-Earth asteroids (NEAs) is crucial for research in solar system and planetary science. In recent year, deep-learning methods have almost dominated the task. Since NEAs represent only one-thousandth of the pixels in images, we proposed an ICC-BiFormer model that includes an image compression and contrast enhancement block and a BiFormer model to capture local features in input images, which is different from previous models based on Convolutional Neural Network (CNN). Furthermore, we utilize a larger input size of the model, which corresponds to the side length of the input image matrix, and design a cropping algorithm to prevent NEAs from being truncated and better divide NEAs and satellites. We apply our ICC-BiFormer model into a dataset of approximately 20,000 streak and 40,000 non-streak images to train a binary classification model. The ICC-BiFormer achieves 99.88% accuracy, which is superior to existing models. Focusing on local features has been proven effective in detecting NEAs.

Active asteroids are those that show evidence of ongoing mass loss. We report repeated instances of particle ejection from the surface of (101955) Bennu, demonstrating that it is an active asteroid. The ejection events were imaged by the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft. For the three largest observed events, we estimated the ejected particle velocities and sizes, event times, source regions, and energies. We also determined the trajectories and photometric properties of several gravitationally bound particles that orbited temporarily in the Bennu environment. We consider multiple hypotheses for the mechanisms that lead to particle ejection for the largest events, including rotational disruption, electrostatic lofting, ice sublimation, phyllosilicate dehydration, meteoroid impacts, thermal stress fracturing, and secondary impacts.

Organic compounds occur in some chondritic meteorites, and their signatures on solar system bodies have been sought for decades. Spectral signatures of organics have not been unambiguously identified on the surfaces of asteroids, whereas they have been detected on cometary nuclei. Data returned by the Visible and InfraRed Mapping Spectrometer on board the Dawn spacecraft show a clear detection of an organic absorption feature at 3.4 micrometers on dwarf planet Ceres. This signature is characteristic of aliphatic organic matter and is mainly localized on a broad region of ~1000 square kilometers close to the ~50-kilometer Ernutet crater. The combined presence on Ceres of ammonia-bearing hydrated minerals, water ice, carbonates, salts, and organic material indicates a very complex chemical environment, suggesting favorable environments to prebiotic chemistry.

The atmospheres of a large proportion of white dwarf stars are polluted by heavy elements 1 that are expected to sink out of visible layers on short timescales 2 , 3 . This has been interpreted as a signature of ongoing accretion of debris from asteroids 4 , comets 5 and giant planets 6 . This scenario is supported by the detection of debris discs 7 and transits of planetary fragments 8 around some white dwarfs. However, photospheric metals are only indirect evidence for ongoing accretion, and the inferred accretion rates and parent body compositions heavily depend on models of diffusion and mixing processes within the white dwarf atmosphere 9 – 11 . Here we report a 4.4 σ detection of X-rays from a polluted white dwarf, G29–38. From the measured X-ray luminosity, we derive an instantaneous accretion rate of M ̇ X = 1.63 − 0.40 + 1.29 × 10 9 g s − 1 , which is independent of stellar atmosphere models. This rate is higher than estimates from past studies of the photospheric abundances of G29–38, suggesting that convective overshoot may be needed to model the spectra of debris-accreting white dwarfs. We measure a low plasma temperature of  k B T = 0.5 ± 0.2 keV, corroborating the predicted bombardment solution for white dwarfs accreting at low accretion rates 12 , 13 . An X-ray source is detected at the expected position of the white dwarf star G29–38, which enables the calculation of the accretion rate of planetary material without using stellar atmosphere models.

We have developed a radar scheme for detecting the asteroid interior structure. Using the auto rotation of an asteroid, radar system can hover at a fix distance from the asteroid, and continuously measure the internal structure echoes at different spin angles, which can be processed to obtain the internal structure profile image. Through simulation and scale model test, we have verified the internal structure imaging results and conformed the effectiveness of the hovering radar method. The proposed radar scheme was selected as the science payload for internal structure in China’s asteroid exploration program aiming at Asteroid 2016HO3.

A machine learning application was developed to detect Potentially Hazardous Asteroid and mitigate asteroid collision risk with the Earth by applying three classifiers: the K-Nearest Neighbors, Naïve Bayes, and Random Forest. The study determined the most effective classifier for developing an asteroid classification program based on orbital motion. The machine learning classifier was then evaluated by its precision, accuracy, F1-score, and recall in determining Potentially Hazardous Asteroids and non-Potentially Hazardous Asteroids. The result presented Random Forest as the most appropriate classifier with the highest accuracy score of 99.53%, followed by the Naive Bayes classifier with an accuracy score of 92.00%, and the KNN classifier with an accuracy score of 84.45%. The study provided information on the most accurate machine learning classifier with the impact parameters for asteroid classification in an early warning system. By improving an embedded real-time detection system for Potentially Hazardous Asteroids, the study contributes to more effective strategies for mitigating the risk of asteroid impacts and enhancing planetary defence.

About 66 million years ago, an asteroid about 10 km in diameter struck the Yucatan Peninsula creating the Chicxulub crater. The crater has been dated and found to be coincident with the Cretaceous–Paleogene (K-Pg) mass extinction event, one of six great mass extinctions in the last 600 million years. This event precipitated one of the largest episodes of rapid climate change in Earth's history, yet no modern three-dimensional climate calculations have simulated the event. Similarly, while there is an ongoing effort to detect asteroids that might hit Earth and to develop methods to stop them, there have been no modern calculations of the sizes of asteroids whose impacts on land would cause devastating effects on Earth. Here, we provide the information needed to initialize such calculations for the K-Pg impactor and for a 1 km diameter impactor. There is considerable controversy about the details of the events that followed the Chicxulub impact. We proceed through the data record in the order of confidence that a climatically important material was present in the atmosphere. The climatic importance is roughly proportional to the optical depth of the material. Spherules with diameters of several hundred microns are found globally in an abundance that would have produced an atmospheric layer with an optical depth around 20, yet their large sizes would only allow them to stay airborne for a few days. They were likely important for triggering global wildfires. Soot, probably from global or near-global wildfires, is found globally in an abundance that would have produced an optical depth near 100, which would effectively prevent sunlight from reaching the surface. Nanometer-sized iron particles are also present globally. Theory suggests these particles might be remnants of the vaporized asteroid and target that initially remained as vapor rather than condensing on the hundred-micron spherules when they entered the atmosphere. If present in the greatest abundance allowed by theory, their optical depth would have exceeded 1000. Clastics may be present globally, but only the quartz fraction can be quantified since shock features can identify it. However, it is very difficult to determine the total abundance of clastics. We reconcile previous widely disparate estimates and suggest the clastics may have had an optical depth near 100. Sulfur is predicted to originate about equally from the impactor and from the Yucatan surface materials. By mass, sulfur is less than 10 % of the observed mass of the spheres and estimated mass of nanoparticles. Since the sulfur probably reacted on the surfaces of the soot, nanoparticles, clastics, and spheres, it is likely a minor component of the climate forcing; however, detailed studies of the conversion of sulfur gases to particles are needed to determine if sulfuric acid aerosols dominated in late stages of the evolution of the atmospheric debris. Numerous gases, including CO2, SO2 (or SO3), H2O, CO2, Cl, Br, and I, were likely injected into the upper atmosphere by the impact or the immediate effects of the impact such as fires across the planet. Their abundance might have increased relative to current ambient values by a significant fraction for CO2, and by factors of 100 to 1000 for the other gases. For the 1 km impactor, nanoparticles might have had an optical depth of 1.5 if the impact occurred on land. If the impactor struck a densely forested region, soot from the forest fires might have had an optical depth of 0.1. Only S and I would be expected to be perturbed significantly relative to ambient gas-phase values. One kilometer asteroids impacting the ocean may inject seawater into the stratosphere as well as halogens that are dissolved in the seawater. For each of the materials mentioned, we provide initial abundances and injection altitudes. For particles, we suggest initial size distributions and optical constants. We also suggest new observations that could be made to narrow the uncertainties about the particles and gases generated by large impacts.

To compare the diagnostic capacity of a color fundus camera (CFC), ultra-wide-field bicolor confocal scanning laser ophthalmoscope (BC-cSLO; OPTOS), and true-color confocal scanning ophthalmoscope (TC-cSO; EIDON) in detecting coexisting retinal diseases in eyes with asteroid hyalosis (AH). The medical records of consecutive patients with AH who were referred to a tertiary hospital for subsequent assessment by a vitreoretinal specialist were retrospectively reviewed. Fundus images obtained simultaneously using CFC, BC-cSLO, and TC-cSO were classified into four grades based on their obscuration by asteroid bodies. The proportion of Grade 1 images (minimal obscuration group) was assessed for each imaging modality. The diagnostic and screening abilities for concurrent retinal diseases were compared in terms of the accuracy and sensitivity of each device. Among the 100 eyes with AH, 76 had coexisting retinal diseases, such as diabetic retinopathy (DR), retinal vascular occlusion, age-related macular degeneration, epiretinal membrane, and retinitis pigmentosa. TC-cSO had the highest ratio of Grade 1 images (94%, P<0.001), followed by CFC (67%) and BC-cSLO (63%). CFC and BC-cSLO exhibited a 5.3-fold higher rate of significant obscuration than TC-cSO (P<0.001, 95% confidence intervals = 2.4~11.6 folds). TC-cSO demonstrated the highest accuracy and sensitivity (95% and 81%, respectively) compared with CFC (89% and 43%, respectively) and BC-cSLO (89% and 39%, respectively) for all retinal diseases. BC-cSLO showed the best performance for DR diagnosis. TC-cSO images showed minimal obscuration and a superior ability for diagnosing retinal diseases accompanied by AH over other imaging devices. TC-cSO can be a valuable alternative screening tool for detecting retinal diseases when AH impedes fundus imaging.

It is important to test the possible existence of fifth forces, as ultralight bosons that would mediate these are predicted to exist in several well-motivated extensions of the Standard Model. Recent work indicated asteroids as promising probes, but applications to real data are lacking so far. Here we use the OSIRIS-REx mission and ground-based tracking data for the asteroid Bennu to derive constraints on fifth forces. Our limits are strongest for mediator masses m  ~ (10 −18 -10 −17 ) eV, where we currently achieve the tightest bounds. These can be translated to a wide class of models leading to Yukawa-type fifth forces, and we demonstrate how they apply to U (1) B dark photons and baryon-coupled scalars. Our results demonstrate the potential of asteroid tracking in probing well-motivated extensions of the Standard Model and ultralight bosons near the fuzzy dark matter range. Asteroid tracking has been demonstrated as a promising and prominent probe of fifth forces arising in several well-motivated models beyond the Standard Model of particle physics. The authors use the state-of-art tracking data for the asteroid Bennu from the OSIRIS-REx mission to derive the tightest limits on fifth forces and ultralight dark matter at the lengths of solar-system objects.

Purpose Asteroids have the characteristics of noncooperative, irregular gravity and complex terrain on the surface, which cause difficulties in successful landing for conventional landers. The purpose of this paper is to study the trajectory tracking problem of a multi-node flexible lander with unknown flexible coefficient and space disturbance. Design/methodology/approach To facilitate the stability analysis, this paper constructs a simplified dynamic model of the multi-node flexible lander. By introducing the nonlinear transformation, a concurrent learning-based adaptive trajectory tracking guidance law is designed to ensure tracking performance, which uses both real-time information and historical data to estimate the parameters without persistent excitation (PE) conditions. A data selection algorithm is developed to enhance the richness of historical data, which can improve the convergence rate of the parameter estimation and the guidance performance. Findings Finally, Lyapunov stability theory is used to prove that the unknown parameters can converge to their actual value and, meanwhile, the closed-loop system is stable. The effectiveness of the proposed algorithm is further verified through simulations. Originality/value This paper provides a new design idea for future asteroid landers, and a trajectory tracking controller based on concurrent learning and preset performance is first proposed.