Near-UV Reddening Observed in the Reflectance Spectrum of High-inclination Centaur 2012 DR30

Centaurs with high orbital inclinations and perihelia (i > 60°; q ≳ 5 au) are a small group of poorly understood minor planets that are predicted to enter the giant planet region of the solar system from the inner Oort Cloud. As such, they are one of the few samples of relatively unaltered Oort Cloud material that can currently be directly observed. Here we present two new reflectance spectra of one of the largest of these objects, 2012 DR30, in order to constrain its color and surface composition. Contrary to reports that 2012 DR30 has variable optical color, we find that consistent measurements of its spectral gradient from most new and published data sets at 0.55–0.8 μm agree with a spectral gradient of S ′ ≃ 10 % ± 1 % / 0.1 μ m within their uncertainties. The spectral variability of 2012 DR30 at near-UV/blue and near-IR wavelengths, however, is still relatively unconstrained; self-consistent rotationally resolved follow-up observations are needed to characterize any spectral variation in those regions. We tentatively confirm previous detections of water ice on the surface of 2012 DR30, and we also consistently observe a steady steepening of the gradient of its spectrum from λ ∼ 0.6 μm toward near-UV wavelengths. Plausible surface materials responsible for the observed reddening may include ferric oxides contained within phyllosilicates and aromatic refractory organics.

Were recently reported MHz events planet mass primordial black hole mergers?

A bulk acoustic wave cavity as high frequency gravitational wave antenna has recently detected two rare events at 5.5MHz. Assuming that the detected events are due to gravitational waves, their characteristic strain amplitude lies at about $$h_c\approx 2.5 \times 10^{-16}$$ h c ≈ 2.5 × 10 - 16 . While a cosmological signal is out of the picture due to the large energy carried by the high frequency waves, the signal could be due to the merging of two planet mass primordial black holes ($$\approx 4\times 10^{-4} M_\odot $$ ≈ 4 × 10 - 4 M ⊙ ) inside the Oort cloud at roughly 0.025 pc (5300 AU) away. In this short note, we show that the probability of one such event to occur within this volume per year is around $$1:10^{24}$$ 1 : 10 24 , if such Saturn-like mass primordial black holes are $$1\%$$ 1 % of the dark matter. Thus, the detected signal is very unlikely to be due the merger of planet mass primordial black holes. Nevertheless, the stochastic background of saturn mass primordial black holes binaries might be seen by next generation gravitational wave detectors, such as DECIGO and BBO.

The Planetary Vaporization Event Hypothesis: Supercharging Earth’s Geothermal Core, Identifying Side Effects Blast Patterns, and Inferring how to Find Earth-Like Planets or Identifying Super Charged Geothermal Cores and their Byproduct Blast Patterns

The supercharged nature of the Earth’s geothermal core can be demonstrated by three thought experiments exhibiting it is tremendously more powerful than any other terrestrial object in the solar system (planet or moon). Identifying a minimum of four byproduct asteroid blast patterns linked to the formation of Earth’s supercharged geothermal core is critical to properly identifying stars that also have these four byproduct asteroid blast patterns. These stars are the most likely to host an Earth-like planet qualified by having a supercharged geothermal core. The Planetary Vaporization-Event (PVE) Hypothesis provides a basis for correlation between the supercharged nature of Earth’s geothermal core and at least 14 listed side effects: (1) the asteroid-wide/planet-scale homogenization and lack thereof of 182W ε for Earth, the Moon, Mars and meteors, (2) the primary and secondary shifting of Earth’s tectonic plates, (3) the solar system wide displacement of Earth’s wayward moons (including Ceres, Pluto, Charon and Orcus) outgassing identical samples of ammoniated phyllosilicates, (4) the formation of asteroids at 100+ times the expected density of a nebular cloud vs. pre-solar grains formation density at the expected density of a nebular cloud, (5) three distinct formation timestamps for all known asteroids within a 5 million year window 4.55+ billion years ago, (6) the estimated formation temperature of CAI at 0.86 billion Kelvin and (7) the remaining chondritic meteorite matrix flash vaporizing at 1,200–1,900 °C, (8) followed by rapid freezing near 0 K, (9) the development of exactly 2 asteroid belts and a swarm of non-moon satellites, (10) particulate size distinction between the 2 asteroid belts of small/inner, large/outer, (11) the proximity of the Trojan Asteroid Groups to the Main Asteroid Belt, (12) observation of a past or present LHB, (13) the development of annual meteor showers for Earth proximal to apogee and/or perigee, (14) the Sun being the most-likely object struck by an asteroid in the inner solar system. Through better understanding of the relevant data at hand and reclassification of the byproducts of supercharging the core of a planet, at least 5 new insights can be inferred and are listed as: (1) the original mass, (2) distance and (3) speed of Earth Mark One, (4) the original order of Earth’s multi-moon formation and (5) the high probability of finding detectable signs of life on a planet orbiting the stars Epsilon Eridani and Eta Corvi. There are at least 6 popular hypothesis that the PVE Hypothesis is in conflict with, listed they are: (1) a giant impact forming the Moon, (2) asteroids being the building blocks of the solar system, (3) the Main Asteroid Belt being the result of a planet that never formed, (4) the LHB being a part of the accretion disk process, (5) the heat in Earth’s core coming primarily from the decay of radioactive elements, (6) the Oort Cloud being the source of ice comets.

First measurement of decimeter-sized rocky material in the Oort cloud

The Oort cloud is thought to be a reservoir of icy planetesimals and a source of long-period comets (LPCs) implanted from the outer Solar System during the time of giant planet formation. The presence of rocky ice-free bodies is much harder to explain. The rocky fraction in the Oort cloud is a key diagnostic of Solar System formation models as this ratio can distinguish between "massive" and "depleted" proto-asteroid belt scenarios and thus disentangle competing planet formation models. Objects of asteroidal appearance have been telescopically observed on LPC orbits, but from reflectance spectra alone it is uncertain whether they are asteroids or extinct comets. Here we report a first direct observation of a decimeter-sized rocky meteoroid on a retrograde LPC orbit (e ≈ 1.0, i = 121°). The ~2 kg object entered the atmosphere at 62 km/s. The associated fireball terminated at 46.5 km, 40 km deeper than cometary objects of similar mass and speed. During its flight, it experienced dynamic pressures of several MPa, comparable to meteorite-dropping fireballs. In contrast, cometary material measured by Rosetta have compressive strengths of ~1 kPa. The earliest fragmentation of this fireball occurred at >100 kPa, indicating it had a minimum global strength well in excess of cometary. A numerical ablation model produces bulk density and ablation properties consistent with asteroidal meteoroids. We estimate the flux of rocky objects impacting Earth from the Oort cloud to be ~0.7 × 106 km2 per year to a mass limit of 10 g. This is ~6% of the total flux of fireballs on LPC-orbits to these masses. Our results suggests there is a high fraction of asteroidal material in the Oort cloud at small sizes and gives support to migration-based dynamical models of the formation of the Solar System which predict that significant rocky material is implanted in the Oort cloud, a result not explained by traditional Solar System formation models.

On the origin of the Kreutz family of sungrazing comets

ABSTRACT We evaluate numerically three different models for the parent comet of the Kreutz family of sungrazers: (i) A Centaur on a highly inclined or retrograde orbit that diffuse to the inner planetary region where it became a sungrazer (Model 1). (ii) A parent comet injected from the Oort cloud straight into a near-parabolic, sungrazing orbit. Near perihelion the comet was disrupted by tidal forces from the Sun giving rise to a myriad of fragments that created the Kreutz family (Model 2). (iii) A two-step process by which an Oort cloud comet is first injected in a non-sungrazing, Earth-crossing orbit where its semimajor axis decreases from typical Oort cloud values (a ∼ 104 au) to around 102 au, and then it evolves to a sungrazing orbit by the Lidov–Kozai mechanism (Model 3). Model 1 fails to produce sungrazers of the Kreutz type. Model 2 produces some Kreutz sungrazers and has the appeal of being the most straightforward. Yet the impulses received by the fragments originated in the catastrophic disruption of the parent comet will tend to acquire a wide range of orbital energies or periods (from short-period to long-period orbits) that is in contradiction with the observations. Model 3 seems to be the most promising one since it leads to the generation of some sungrazers of the Kreutz type and, particularly, it reproduces the clustering of the argument of perihelion ω of the observed Kreutz family members around 60°–90°, as a natural consequence of the action of the Lidov–Kozai mechanism.

C/2010 U3 (Boattini): A Bizarre Comet Active at Record Heliocentric Distance

<p>We report an identification of long-period comet C/2010 U3 (Boattini) active at a new record inbound heliocentric distance of <em>r</em><sub>H</sub> ≈ 26 au. Two outburst events around 2009 and 2017 were observed. The dust morphology of the coma and tail cannot be explained unless the Lorentz force, solar gravitation, and solar radiation pressure force are all taken into account. Optically dominant dust grains have radii of ~10 μm and are ejected protractedly at speeds ≤50 m s<sup>−1</sup> near the subsolar point. The prolonged activity indicates that sublimation of supervolatiles (e.g., CO, CO<sub>2</sub>) is at play. Similar to other long-period comets, the colour of the cometary dust is redder than the solar colours. We also observed potential colour variations when the comet was at 10 < <em>r</em><sub>H</sub> < 15 au, concurrent with the onset of crystallisation of amorphous water ice, if any. Using publicly available and our refined astrometric measurements, we estimated the precise trajectory of the comet, propagated it backward to its previous perihelion, and found that the comet visited the planetary region ~2 Myr ago at perihelion distance <em>q</em> ≈ 8 au. Thus, C/2010 U3 (Boattini) is almost certainly a dynamically old comet from the Oort cloud, and the observed activity cannot be caused by retained heat from the previous apparition. The detailed study is presented in Hui et al. (2019, AJ, 157, 162).</p>

Meteoroids as Source for Mercury’s exosphere

<p>The study of the meteoroid environment for particles with masses in the 1 μg - 10 g range is relevant to planetary science, space weathering of airless bodies and their upper atmospheric chemistry. For the case of airless bodies as Mercury, meteoroids hit their surfaces directly, producing impact debris and contributing to shape their thin exospheres.</p> <p>Mercury is a unique case in the solar system: absence of an atmosphere and the weakness of the intrinsic magnetic field. The Hermean exosphere is continuously eroded and refilled by interactions between plasma and surface, so the environment is considered as a single, unified system surface- exosphere-magnetosphere. The study of the generation mechanisms, the compositions and the configuration of the Hermean exosphere will provide crucial insight in the planet status and evolution. A global description of planet’s exosphere is still not available: missions visited Mercury and added a consistent amount of data, but still the actual knowledge about the morphology of this tenuous atmosphere is anyway poor. The ESA BepiColombo mission will study Mercury in details, by orbiting around the planet from 2025. For this reason, it is important to study the planet exospheric density and to develop a modelling tool ready for testing different hypothesis on the release mechanisms and for interpreting future observational data.</p> <p>In this work we focus the attention on one of the processes responsible of the Mercury’s Ca exosphere formation: micro-meteoroids impact vaporization (MMIV) from the planetary surface. <span lang="EN-US">A prototype of the Virtual Activity (VA) SPIDER (Sun-Planet Interactions Digital Environment on Request) services is used as a Monte Carlo three-dimensional model of the Hermean exosphere to simulate the bombardment of Mercury’s surface by micrometeorites from different sources, as Jupiter Family Comets (JFCs), Main Belt Asteroids (MBA), Halley Type and Oort Cloud Comets (HTCs and OCCs), and to analyze particles ejected. </span>We study how the impact vapor varies with heliocentric distance and the high impact velocity of these particles makes them critical for the morphology of Mercury exosphere, demonstrating a persistent enhancement of dust/meteoroid at dawn, which should be responsible of the dawn–dusk asymmetry in Mercury’s Ca exosphere.</p> <p> </p> <p><sub>The <em>Sun Planet Interactions Digital Environment on Request (SPIDER) Virtual Activity of the Europlanet H2024 Research Infrastucture is funded by the European Union's Horizon 2020 research </em></sub></p> <p><sub><em>and innovation programme under grant agreement No 871149.</em></sub></p>