Spin vectors in the Koronis family: V. Resolving the ambiguous rotation period of (3032) Evans

A sidereal rotation counting approach is demonstrated by resolving an ambiguity in the synodic rotation period of Koronis family member (3032) Evans, whose rotation lightcurves' features did not easily distinguish between doubly- and quadruply-periodic. It confirms that Evans's spin rate does not exceed the rubble-pile spin barrier and thus presents no inconsistency with being a ~14-km reaccumulated object. The full spin vector solution for Evans is comparable to those for the known prograde low-obliquity comparably-fast rotators in the Koronis family, consistent with having been spun up by YORP thermal radiation torques.Comment: 8 pages, 6 figures, accepted for publication in Icaru

Twenty years of SpeX: Accuracy limits of spectral slope measurements in asteroid spectroscopy

We examined two decades of SpeX/NASA Infrared Telescope Facility observations from the Small Main-Belt Asteroid Spectroscopic Survey (SMASS) and the MIT-Hawaii Near-Earth Object Spectroscopic Survey (MITHNEOS) to investigate uncertainties and systematic errors in reflectance spectral slope measurements of asteroids. From 628 spectra of 11 solar analogs used for calibration of the asteroid spectra, we derived an uncertainty of 4.2%/micron on slope measurements over 0.8 to 2.4 micron. Air mass contributes to -0.92%/micron per 0.1 unit air mass difference between the asteroid and the solar analog, and therefore for an overall 2.8%/micron slope variability in SMASS and MITHNEOS designed to operate within 1.0 to 1.3 air mass. No additional observing conditions (including parallactic angle, seeing and humidity) were found to contribute systematically to slope change. We discuss implications for asteroid taxonomic classification works. Uncertainties provided in this study should be accounted for in future compositional investigation of small bodies to distinguish intrinsic heterogeneities from possible instrumental effects.Comment: 15 pages, 11 figures, accepted for publication in ApJ

The Massalia asteroid family as the origin of ordinary L chondrites

Studies of micrometeorites in mid-Ordovician limestones and Earth's impact craters indicate that our planet witnessed a massive infall of ordinary L chondrite material 466 million years (My) ago (Heck et al. 2017, Schmieder & Kring 2020, Kenkmann 2021) that may have been at the origin of the first major mass extinction event (Schmitz et al. 2019). The breakup of a large asteroid in the main belt is the likely cause of this massive infall. In modern times, material originating from this breakup still dominates meteorite falls (>20% of all falls) (Swindle et al. 2014). Here, we provide spectroscopic observations and dynamical evidence that the Massalia collisional family is the only plausible source of this catastrophic event and of the most abundant class of meteorites falling on Earth today. It is suitably located in the inner belt, at low-inclination orbits, which corresponds to the observed distribution of L-chondrite-like near-Earth objects (NEOs) and of interplanetary dust concentrated at 1.4 degrees (Sykes 1990, Reach et al. 1997).Comment: 35 pages, 11 pages, under revisio

The Debiased Compositional Distribution of MITHNEOS : Global Match between the Near-Earth and Main-belt Asteroid Populations, and Excess of D-type Near-Earth Objects

We report 491 new near-infrared spectroscopic measurements of 420 near-Earth objects (NEOs) collected on the NASA InfraRed Telescope Facility as part of the MIT-Hawaii NEO Spectroscopic Survey. These measurements were combined with previously published data from Binzel et al. and bias-corrected to derive the intrinsic compositional distribution of the overall NEO population, as well as of subpopulations coming from various escape routes (ERs) in the asteroid belt and beyond. The resulting distributions reflect well the overall compositional gradient of the asteroid belt, with decreasing fractions of silicate-rich (S- and Q-type) bodies and increasing fractions of carbonaceous (B-, C-, D- and P-type) bodies as a function of increasing ER distance from the Sun. The close compositional match between NEOs and their predicted source populations validates dynamical models used to identify ERs and argues against any strong composition change with size in the asteroid belt between similar to 5 km and similar to 100 m. A notable exception comes from the overabundance of D-type NEOs from the 5:2J and, to a lesser extend, the 3:1J and nu (6) ERs, hinting at the presence of a large population of small D-type asteroids in the main belt. Alternatively, this excess may indicate preferential spectral evolution from D-type surfaces to C and P types as a consequence of space weathering, or point to the fact that D-type objects fragment more often than other spectral types in the NEO space. No further evidence for the existence of collisional families in the main belt, below the detection limit of current main-belt surveys, was found in this work.Peer reviewe

Spin axis of (2953) Vysheslavia and its implications

International audiencePhotometric observations made during the years 2000-2005 are used to determine the pole orientation of (2953) Vysheslavia, a ~=15-km size member of the Koronis family. We find admissible solutions for ecliptic latitude and longitude of the rotation pole P: beta=-64°±10° and lambda=11°±8° or P: beta=-68°±8° and lambda=192°±8°. These imply obliquity values gamma=154°±14° and gamma=157°±11°, respectively. The sidereal rotation period is P=0.2622722±0.0000018 day. This result is interesting for two reasons: (i) the obliquity value between 90° and 180° is consistent with a prediction done by Vokrouhlický et al. [Vokrouhlický, D., Broz, M., Farinella, P., Knezevic, Z., 2001. Icarus 150, 78-93] that Vysheslavia might have been transported to its unstable orbit by the Yarkovsky effect, and (ii) with the obliquity close to 180°, Vysheslavia seems to belong to one of the two distinct groups in the Koronis family found recently by Slivan [Slivan, S.M., 2002. Nature 419, 49-51], further supporting the case of dichotomy in the spin axis distribution in this family. We also argue against the possibility that Vysheslavia reached its current orbit by a recent collisional breakup

Connecting asteroids and meteorites with visible and near-infrared spectroscopy

International audienceIn this work we identify spectral similarities between asteroids and meteorites. Using spectral features such as absorption bands and spectral curvature, we identify spectral matches between 500 asteroid spectra and over 1,000 samples of RELAB meteorite spectra over visible plus near-infrared wavelengths (0.45- 2 . 5 μm). We reproduce and confirm many major and previously known meteorite-asteroid connections and find possible new, more rare or less-established connections. Well-established connections include: ordinary chondrites with S-complex asteroids; pristine CM carbonaceous chondrites with Ch-type asteroids and heated CMs with C-type asteroids ; HED meteorites with V-types; enstatite chondrites with Xc-type asteroids; CV meteorites with K-type asteroids; Brachinites, Pallasites and R chondrites with olivine-dominated A-type asteroids. In addition to the link between ordinary chondrite meteorites with S-complex asteroids, we find a trend from Q, Sq, S, Sr to Sv correlates with LL to H, with Q-types matching predominately to L and LL ordinary chondrites, and Sr and Sv matching predominantly with L and H ordinary chondrites. We find ordinary chondrite samples that match to the X-complex. These are measurements of slabs and many are labeled as dark or black (shocked) ordinary chondrites. We find carbonaceous chondrite samples having spectral slopes large enough to match D-type asteroid spectra. We find in many cases the asteroid type to meteorite type links are not unique, for classes with and without distinct spectral features. While there are examples of dominant matches between an asteroid class and meteorite class that are well established, there are less common but still spectrally compatible matches between many asteroid types and meteorite types. This result emphasizes the diversity of asteroid and meteorite compositions and highlights the degeneracy of classification by spectral features alone requiring additional measurements to firmly establish asteroid-meteorite links. Recent and upcoming spacecraft missions will shed light on the compositions of many of the asteroid classes, particularly those without diagnostic features, (C-, B-, X-, and D-types), with measurements of C-type Ceres, C-type Ryugu, B-type Bennu, M-type Psyche, and C-, P-, and D-types as part of the Lucy mission

Size and Shape Constraints of (486958) Arrokoth from Stellar Occultations

International audienceWe present the results from four stellar occultations by (486958) Arrokoth, the flyby target of the New Horizons extended mission. Three of the four efforts led to positive detections of the body, and all constrained the presence of rings and other debris, finding none. Twenty-five mobile stations were deployed for 2017 June 3 and augmented by fixed telescopes. There were no positive detections from this effort. The event on 2017 July 10 was observed by the Stratospheric Observatory for Infrared Astronomy with one very short chord. Twenty-four deployed stations on 2017 July 17 resulted in five chords that clearly showed a complicated shape consistent with a contact binary with rough dimensions of 20 by 30 km for the overall outline. A visible albedo of 10% was derived from these data. Twenty-two systems were deployed for the fourth event on 2018 August 4 and resulted in two chords. The combination of the occultation data and the flyby results provides a significant refinement of the rotation period, now estimated to be 15.9380 ± 0.0005 hr. The occultation data also provided high-precision astrometric constraints on the position of the object that were crucial for supporting the navigation for the New Horizons flyby. This work demonstrates an effective method for obtaining detailed size and shape information and probing for rings and dust on distant Kuiper Belt objects as well as being an important source of positional data that can aid in spacecraft navigation that is particularly useful for small and distant bodies