Lunar-like silicate material forms the Earth quasi-satellite (469219) 2016 HO3 Kamoʻoalewa

Little is known about Earth quasi-satellites, a class of near-Earth small solar system bodies that orbit the sun but remain close to the Earth, because they are faint and difficult to observe. Here we use the Large Binocular Telescope (LBT) and the Lowell Discovery Telescope (LDT) to conduct a comprehensive physical characterization of quasi-satellite (469219) Kamoʻoalewa and assess its affinity with other groups of near-Earth objects. We find that (469219) Kamoʻoalewa rotates with a period of 28.3 (+1.8/−1.3) minutes and displays a reddened reflectance spectrum from 0.4–2.2 microns. This spectrum is indicative of a silicate-based composition, but with reddening beyond what is typically seen amongst asteroids in the inner solar system. We compare the spectrum to those of several material analogs and conclude that the best match is with lunar-like silicates. This interpretation implies extensive space weathering and raises the prospect that Kamo’oalewa could comprise lunar material.

Spectral properties of near-Earth objects with low-Jovian Tisserand invariant

ABSTRACT The near-Earth objects with low-Jovian Tisserand invariant (TJ) represent about 9 per cent of the known objects orbiting in the near-Earth space, being subject of numerous planetary encounters and large temperature variations. We aim to make a spectral characterization for a large sample of NEOs with TJ ≤ 3.1. Consequently, we can estimate the fraction of bodies with a cometary origin. We report new spectral observations for 26 low-TJ NEOs. The additional spectra, retrieved from different public data bases, allowed us to perform the analysis over a catalogue of 150 objects. We classified them with respect to Bus-DeMeo taxonomic system. The results are discussed regarding their orbital parameters. The taxonomic distribution of low-TJ NEOs differs from the entire NEOs population. Consequently, TJ ∼ 3 can act as a composition border too. We found that 56.2 per cent of low-TJ NEOs have comet-like spectra and they become abundant (79.7 per cent) for TJ ≤ 2.8. 16 D-type objects have been identified in this population, distributed on orbits with an average TJ = 2.65 ± 0.6. Using two dynamical criteria, together with the comet-like spectral classification as an identification method and by applying an observational bias correction, we estimate that the fraction of NEOs with a cometary nature and H ∈ (14, 21) mag has the lower and upper bounds (1.5 ± 0.15) and (10.4 ± 2.2) per cent. Additionally, our observations show that all extreme cases of low-perihelion asteroids (q ≤ 0.3 au) belong to S-complex.

THE CHANGING EVENT SURVEY: TRANSIENTS, SPACE DEBRIS & NEOs

Motivated by the promising era of time-domain and multi-messenger astronomy, CHanging Event Survey (CHES) is designed to join the ongoing campaign with a powerful wide-field optical telescope array. CHES project aims to monitor the transient universe, including gamma-ray bursts, fast radio bursts, the electromagnetic counterpart of gravitational waves events (kilonova), supernova, variable stars, near-earth objects, and space debris. The array consists of 12 individual wide field refractors with aperture 280 mm, covering 600 square degrees in total. In the same project, two 800 mm prime focus telescopes can be triggered for follow-up observation. Furthermore, CHES can effectively monitor 300 square deg in a dual band simultaneously, which enable the array to do candidate identification and follow-up for the triggers from LIGO/Virgo collaboration, Fermi, Swift, GECam and SVOM satellites.

Hayabusa2 Returned Samples: First Results From the MicrOmega Investigation Within the ISAS Curation Facility

<p><strong>Introduction:</strong> On December 6, 2020, the Hayabusa2 mission successfully returned to Earth ~ 5.4 g of samples collected at the surface of the C-type asteroid Ruygu [1,2]. Its surface was first sampled on February 22, 2019, then on July 12, 2019, close to a 10-meter large artificial crater, so as to possibly access sub-surface material [3]. The collected samples are now kept at the Extraterrestrial Samples Curation Center of JAXA at ISAS in Sagamihara, Japan, for a first round of preliminary analyses, with the objective to characterize in a non-destructive manner both the bulk samples and a few hundreds of grains extracted from them [4]. In particular, the objective is 1) to support their further detailed characterization by the international initial analysis teams, which will start their activity in July 2021, and 2) to catalog the grains, accessible to the international community through AO selection, starting mid-2022.</p> <p>The preliminary characterization of these samples is being conducted with a visible microscope with four color filters, a FTIR spectrometer operating in the 1-5 µm range and MicrOmega, a hyperspectral NIR microscope developed at Institut d'Astrophysique Spatiale (Université Paris-Saclay/CNRS, Orsay, France), operating in the near-infrared range (0.99-3.65 µm) [5]. It is noteworthy that never before have the preliminary analyses of returned extraterrestrial samples included the characterization by a NIR hyperspectral microscope.</p> <p><strong>Results: </strong>Preliminary outcomes of the analyses performed with MicrOmega will be presented at the conference. In particular, the question of the representativity of the samples collected by the Hayabusa2 spacecraft will be addressed thanks to the comparison of the spectra obtained by MicrOmega and the NIRS3 remote sensing IR spectrometer [6] which performed a spectral characterization (1.8-3.2 µm) of Ryugu's surface, including the sites of the samples' collection [7,8]. A preliminary analysis of the spatial compositional heterogeneity will be presented. Specific signatures, detected in grains typically present in <1% of the pixels, but of high relevance regarding the processes determining Ryugu formation and evolution, will also be discussed.</p> <p><strong>References: </strong>[1] Binzel R. P. et al. (2002), Physical Properties of Near-Earth Objects. pp. 255-271, [2] Vilas F. (2008) <em>The Astronomical Journal</em> 135 (4), 1101-1105, [3] Morota et al. (2020) <em>Science</em> 368, Issue 6491, pp. 654-659, [4] Yada T. et al., in preparation, [5] Bibring J.-P. et al. (2017) <em>Astrobiology</em> 17, Issue 6-7, pp.621-626, [6] Iwata T. et al. (2017) <em>Space Science Reviews</em> 208 (1-4), 317-337, [7] Kitazato K. et al. (2019) <em>Science</em> 364 (6437), 272-275, [8] Kitazato K. et al. (2020) <em>Nature Astronomy</em>, Volume 5, p. 246-250.</p>