^1,2M.N.DePrá,^3,4J.Licandro,¹N.PinillaAlonso,³V.Lorenzie,²E.Rondón,²J.Carvano,²D.Morate,^3,4J.De León
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.113473]
¹Florida Space Institute, University of Central Florida, FL, USA
²Departamento de Astrofísica, Observatório Nacional, Rio de Janeiro, 20921-400, Brazil
³Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, 38205 La Laguna, Spain
⁴Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁵Fundación Galileo Galilei – INAF, Rambla José Ana Fernández Pérez, 7, 38712 Breña Baja, Santa Cruz de Tenerife, Spain
Copyright Elsevier

The Lixiaohua collisional family lies in the Outer Main Belt, close to the well characterized Themis primitive class family. It is one of the only three families that host two active asteroids that present cometary-like activity: 313P/ Gibbs and 358P/PANSTARRS (P/2012 T1). As a part of the PRIMitive Asteroid Spectoscopy Survey (PRIMASS), we present the results of a spectroscopic program where we acquired 36 objects in visible wavelengths, using the 4.1 m SOAR, and, 17 objects in the near-infrared, using the 3.58m Telescopio Nazionale Galileo, which provided the characterization of 43 out of the 756 identified Lixiaohua family members. We observed asteroids members of the Lixiaohua family with the aim of: (1) determining the spectral class and spectroscopic properties of the family, (2) estimating the presence of hydrated minerals on their surfaces by studying the 0.7 μm absorption band and the UV drop of reflectance below 0.5 μm, (3) analyzing if active asteroids 358P and 313P are probable family members. Our results show that the Lixiaohua family is consistently redder families than the Themis family and present a wide variety of slopes. We haven’t found an unambiguous trace of aqueous alteration in the spectra of the family members, at the observed wavelengths. Finally, we conclude that the Lixiaohua family is the probable source of the Main-Belt Comets 313P/ Gibbs and 358P/PANSTARRS.

¹J.P.Pabari,¹S.Nambiar,²V.Shah,¹A.Bhardwaj
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2019.113510]
¹PRL, Ahmedabad, India
²CSPIT, Changa, India
Copyright Elsevier

Dust particles exist everywhere in interplanetary space and they evolve dynamically after their origination from the sources like Asteroid belt, Kuiper belt, comets or space debris left during the formation of solar system. These micrometeorites encounter the inner planets, while they spiral-in towards the Sun. From whichever come to Earth, many particles are ablated in the Earth’s atmosphere and leave the metallic ions behind. In case of Moon, all such particles can reach the surface without ablation owing to the absence of atmosphere. Due to the impact of hypervelocity dust particles on lunar surface, ejecta come out in the lunar environment. In some cases, the ejecta velocity could be larger than the escape velocity and particles may be able to escape from Moon. Further, the escaping ejecta may carry water ice (volatiles), whenever incoming projectiles hit the surface in polar region with the water ice present. In this paper, we have computed the ejecta parameters and estimated the possible escape of volatiles from Moon, using Galileo observations of the dust particles near Moon. Considering the incident angle distribution, the upper limit of regolith escape rate is found to be ~2.218 × 10−4 [1.662 × 10−4, 10.232 × 10−4] kg/s. Similarly, the upper limit of water ice escape rate is found to be ~1.988 × 10−7 [1.562 × 10−7, 7.567 × 10−7] kg/s. On one side, Moon is found to be gradually becoming heavier due to its one order higher incoming dust particles than those escaping from it. While on the other side, Moon could be depleted of water ice (volatiles) resources over a period of time, because of the escape due to micrometeorite impact. The results presented here could be useful to understand the dust and volatile escape from Moon.

^1,2,3Zhuang Guo,^1,2 YangLi,²Shen Liu,⁵Huifang Xu,^1,4Shijie Li,^1,4Xiongyao Li,⁶Yangting Lin,⁷Ian M.Coulson,^1,4Mingming Zhang
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2019.10.036]
¹Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China
²State Key Laboratory of Continental Dynamics and Department of Geology, Northwest University, Xi’an 710069, China
³University of Chinese Academy of Sciences, Beijing 100049, China
⁴Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, China
⁵Department of Geoscience, University of Wisconsin-Madison, Madison, Wisconsin 53706-1692, USA
⁶Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
⁷Solid Earth Studies Laboratory, Department of Geology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada
Copyright Elsevier

Although pure metallic iron (i.e. that with an Fe content of greater than 99%) commonly occurs in achondrites, and within the returned soil from asteroids or the Lunar surface, it is rarely found in ordinary chondrites meteorites. Abundant nanophase iron particles (np-Fe⁰) were identified in pyroxene glass, within the shock melt vein of Grove Mountains (GRV) 022115, which is an ordinary (L6) chondrite, with a shock stage determined as S5. The association of np-Fe⁰, highly defective high pressure clinoenstatite (HP-CEn), silica glass, as well as vesicles, embedded in a pyroxene glass selvage within the shock melt vein in this meteorite suggests that these phases formed as the result of decomposition of the host pyroxene grain, a process induced by the shock event that affected GRV 022115. The reaction to account for this mineral breakdown can be written as: FeSiO₃ →Fe + SiO₂ + 1/2O₂ ↑ (MgSiO₃ remain in the HP-CEn). The pressure and temperature condition attending this reaction are estimated at 20-23 GPa and over 1800 ℃, as indicated by the surrounded high-pressure mineral assemblage: ringwoodite, majorite, and magnesiowüstite. This study provides evidence to the formation of np-Fe⁰ derived from pyroxene, and HP-CEn quenched metastably in such shocked vein could preserve the metastable phase transitions history record.