This project studies the physical and compositional properties of the so-called minor bodies of the Solar System, that includes asteroids, icy objects, and comets. Of special interest are the trans-neptunian objects (TNOs), including those considered the most distant objects detected so far (Extreme-TNOs or ETNOs); the comets and the comet-asteroid transitional objects (Centaurs and main belt comets or MBCs); the primitive asteroids. The last two groups contain the most primordial and pristine material of the Solar System and so they provide the clues to understand the origin and the subsequent evolution of our system. Among asteroid population, the near-Earth asteroids or NEAs, as well as the potentially hazardous asteroids (PHAs) are of particular interest: due to their proximity to the Earth, they are the most accesible to spacecraft and so are ideal for in-situ or even sample-return space missions. In addition they are considered as future potential resources of materials (asteroid mining), and they are also impact hazards for the Earth. Regarding primitive asteroids, it is remarkable the spectroscopic survey (visible and near-infrared) led by the PI of this project (PRIMitive Asteroids Spectroscopic Survey - PRIMASS). This survey received financial support from NASA (17-PDART17_2-0097, PI: N. Pinilla-Alonso, 137.000€ - 2 years) in order to upload and archive at the Small Bodies Node of the NASA Planetary Data System the more than 800 spectra obtained.
The compositional surface properties, as well as the physical and thermal properties of these objects are inferred through imaging, photometry, and spectroscopy in a wide range of wavelengths (from 0.35 up to 24 microns). Data are interpreted using scattering and thermo-physical models. This project works also in the study of the physical properties of the cometary nuclei, as well as properties of dust and coma in the tails of the MBCs and the mechanisms that generate them.
This group maintains several international collaborations with other groups, and some of their members are also members of (1) the Science Team of the NASA OSIRIS-REx mission, in particular the Image Processing Working Group, were they work with the images obtained with the OCAMS suite of cameras; (2) the coordination of an international group to study NEAs (EURONEAR); (3) the central core of the proponents of ESA M5 missions CASTALIA, CASTAway, and Hera; (4) the Center for Lunar and Asteroid Surface Science - CLASS (NASA); (5) the Solar System group of the Euclid consortium; (6) the surveys J-PLUS and J-PASS for the exploitation of observations of Solar System objects; (7) the Solar System working group of Gaia and JWST.
First asteroid gas sample delivered by the Hayabusa2 mission: A treasure box from Ryugu
The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on 6 December 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial 3He/4He and 20Ne/22Ne ratiosOkazaki R. et al et al.
A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu
Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through a collective process called space weathering. The return of samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory
Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites
Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measure the mineralogy, bulk chemical and isotopic compositions of Ryugu samples. They are mainly composed of materials similar to carbonaceous chondrite meteoritesYokoyama, T. et al.
Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples
Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed seventeen Ryugu samples measuring 1-8 mm. CO2-bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials thatNakamura T. et al. et al.
Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution
The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth’s volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measure noble gas and nitrogen isotopes in Ryugu samples, finding they are dominated by pre-solar and primordialOkazaki R. et al et al.
Site selection for the Hayabusa2 artificial cratering and subsurface material sampling on Ryugu
Hayabusa2 took on the challenge of collecting fresh subsurface samples from asteroid (162173) Ryugu during its second touchdown operation. For this ambitious goal, the spacecraft conducted artificial cratering by using a small carry-on impactor (SCI), leading to the exposure of subsurface materials. The key to mission success lies in the targetKikuchi, Shota et al.
Resurfacing processes constrained by crater distribution on Ryugu
Understanding the geological modification processes on asteroids is fundamental for elucidating their surface evolution. Images of small asteroids from spacecrafts show a depletion in smaller craters. Seismic shaking was considered to be responsible for erasing such small craters and the main driver modifying the geology of asteroids. However, aTakaki, Naofumi et al.
Pebbles and sand on asteroid (162173) Ryugu: In situ observation and particles returned to Earth
The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. The mission performed two landing operations to collect samples of surface and subsurface material, the latter exposed by an artificial impact. We present images of the second touchdown site, finding that ejecta from the impact crater was present at the sampleWatanabe, S. et al.
Detection of the Irregular Shape of the Southern Limb of Menoetius from Observations of the 2017-2018 Patroclus-Menoetius Mutual Events
This work presents the analysis of seven mutual events of the Patroclus-Menoetius system (PMS) observed during the last season of mutual events, in 2017-2018. We compare the obtained light curves with those predicted using Grundy et al. and discuss the differences in the timing of the events and the drop of magnitude. Based on models of thesePinilla-Alonso, Noemí et al.
Characterization of the MASCOT landing area by Hayabusa2
Context. After landing on C-type asteroid Ryugu, MASCOT imaged brightly colored, submillimeter-sized inclusions in a small rock. Hayabusa2 successfully returned a sample of small particles from the surface of Ryugu, but none of these appear to harbor such inclusions. The samples are considered representative of Ryugu. Aims: To understand theSchröder, Stefan et al.
Particle size distributions inside and around the artificial crater produced by the Hayabusa2 impact experiment on Ryugu
Japanese Hayabusa2 spacecraft has successfully carried out an impact experiment using a small carry-on impactor (SCI) on an asteroid (162173) Ryugu. We examine the size distribution of particles inside and outside an artificial impact crater (the SCI crater) based on the images taken by the optical navigation camera onboard the Hayabusa2 spacecraftOgawa, K. et al.
A pristine record of outer Solar System materials from asteroid Ryugu's returned sample
Volatile and organic-rich C-type asteroids may have been one of the main sources of Earth's water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but the meteorite record is biased: only the strongest types survive atmospheric entry and are then modified by interaction with the terrestrialIto, Motoo et al.
Spectral Rotational Characterization of the Didymos System prior to the DART Impact
The smallest member of the Didymos binary near-Earth object system (Dimorphos) is the target of the DART/LICIACube mission, the first attempt to change the orbit of another celestial body via a kinetic impactor. It is important to characterize the unperturbed system prior to the DART impact. In this work we obtained, for the first time, spectralIeva, Simone et al.
Near-ultraviolet to visible spectroscopy of the Themis and Polana-Eulalia complex families
Context. Spectrophotometry data of asteroids obtained in the 1980s showed that there are large variations in their near-ultraviolet (NUV) reflectance spectra. Reflectance spectra at NUV wavelengths are important because they help detect the presence of hydrated minerals and organics on the asteroid surfaces. However, the NUV wavelength region hasTatsumi, E. et al.
Photometric Observations of the Binary Near-Earth Asteroid (65803) Didymos in 2015-2021 Prior to DART Impact
We performed photometric observations of the binary near-Earth asteroid (65803) Didymos in support of the Double Asteroid Redirection Test (DART) mission that will test the Kinetic Impactor technology for diverting dangerous asteroids. It will hit the Didymos secondary, called Dimorphos, on 2022 September 26. We observed Didymos with 11 telescopesPravec, P. et al.
The EURONEAR Lightcurve Survey of Near Earth Asteroids 2017-2020
This is the fourth data paper publishing lightcurve survey work of 52 Near Earth Asteroids (NEAs) using 10 telescopes available to the EURONEAR network between 2017 and 2020. Forty six targets were not observed before our runs (88% of the sample) but some of these were targeted during the same oppositions mainly by Brian Warner. We propose newVaduvescu, O. et al.
Apophis Planetary Defense Campaign
We describe results of a planetary defense exercise conducted during the close approach to Earth by the near-Earth asteroid (99942) Apophis during 2020 December-2021 March. The planetary defense community has been conducting observational campaigns since 2017 to test the operational readiness of the global planetary defense capabilities. TheseReddy, Vishnu et al.
A comprehensive study of the opposition effect on 15 NEOs
We report the results we derived analyzing photometric measurements obtained at different phase angles for 15 Near-Earth Objects (NEOs), observed from Campo Imperatore observatory, and Observatório Astronômico do Sertão de Itaparica (OASI). The performed analysis allows us to taxonomically classify them using several independent techniques, thusIeva, S. et al.
Three-axial shape distributions of pebbles, cobbles and boulders smaller than a few meters on asteroid Ryugu
Over a broad size range, the shapes of impact fragments from catastrophic disruptions are distributed around the mean axial ratio 2: √2: 1, irrespective of experimental conditions and target materials. Although most blocks on asteroids are likely to be impact fragments, there is not enough quantitative data for reliable statistics on their threeMichikami, Tatsuhiro et al.
Physical and dynamical characterization of hyperbolic comet C/2017 U7 (PANSTARRS)
We present here a dynamical and observational study of the comet C/2017 U7 (PANSTARRS). This comet was discovered in 2017 and found to have a hyperbolic orbit. Our dynamical analysis shows that the object has probably originated in the Oort cloud, however an interstellar origin cannot be discarded. The observations were obtained in 2018 and 2019Evangelista-Santana, M. et al.
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