The near-Earth carbonaceous asteroid 162173 Ryugu is thought to have been produced from a parent body that contained water ice and organic molecules. The Hayabusa2 spacecraft has obtained global multi-color images of Ryugu. Geomorphological features present include a circum-equatorial ridge, east/west dichotomy, high boulder abundances across the entire surface, and impact craters. Age estimates from the craters indicate a resurfacing age of ≲106 years for the top 1-meter layer. Ryugu is among the darkest known bodies in the Solar System. The high abundance and spectral properties of boulders are consistent with moderately dehydrated materials, analogous to thermally metamorphosed meteorites found on Earth. The general uniformity in color across Ryugu’s surface supports partial dehydration due to internal heating of the asteroid’s parent body.

The science operations of the spacecraft and remote sensing instruments for the Martian Moon eXploration (MMX) mission are discussed by the mission operation working team. In this paper, we describe the Phobos observations during the first 1.5 years of the spacecraft’s stay around Mars, and the Deimos observations before leaving the Martian system. In the Phobos observation, the spacecraft will be placed in low-altitude quasi-satellite orbits on the equatorial plane of Phobos and will make high-resolution topographic and spectroscopic observations of the Phobos surface from five different altitudes orbits. The spacecraft will also attempt to observe polar regions of Phobos from a three-dimensional quasi-satellite orbit moving out of the equatorial plane of Phobos. From these observations, we will constrain the origin of Phobos and Deimos and select places for landing site candidates for sample collection. For the Deimos observations, the spacecraft will be injected into two resonant orbits and will perform many flybys to observe the surface of Deimos over as large an area as possible. Graphical Abstract

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Abstract. The present case report presents a rare case of Epstein-Barr virus (EBV)-associated early gastric carcinoma with lymphoid stroma, accompanied by lymph node metastasis. A 61-year-old woman was referred to our hospital following observation of a gastric mass lesion that was initially diagnosed at a medical check-up. Esophagogastroduodenoscopy revealed a slightly elevated lesion with a central irregular depression in the middle third of the stomach. Endoscopic ultrasonography revealed a well-circumscribed hypoechoic mass located predominantly within the submucosa and the mucosa. Biopsy specimens of the lesion indicated the possibility of carcinoma with lymphoid stroma with a lymphoepithelial lesion. Abdominal contrast-enhanced computed tomography (CT) revealed a well-defined mass with homogeneous enhancement approximately 1.2 cm in diameter in the middle part of the stomach, demonstrating lymphadenopathy in the perigastric area at a maximum size of 1.4 cm in diameter. The patient underwent laparoscopic distal gastrectomy with regional lymphadenectomy due to suspicion of a gastric carcinoma with lymphoid stroma. Histopathological and immunohistochemical findings verified the diagnosis of carcinoma with lymphoid stroma, which were positive for EBV-encoded RNA (EBER-ISH) by in situ hybridization. There was one lymph node metastasis, which was in line with the CT imaging. Marked infiltration of lymphoid cells was observed in the tumor stroma, which were negative for EBER-ISH. The present case is informative of the pathological characteristics of this condition, and clinicians should recognize the features of this disease to make an accurate diagnosis and select the appropriate treatment.

In late 2018, the asteroid Ryugu was in the Sun’s shadow during the superior solar conjunction phase. As the Sun-Earth-Ryugu angle decreased to below 3°, the Hayabusa2 spacecraft experienced 21 days of planned blackout in the Earth-probe communication link. This was the first time a spacecraft had experienced solar conjunction while hovering around a minor body. For the safety of the spacecraft, a low energy transfer trajectory named Ayu was designed in the Hill reference frame to increase its altitude from 20 to 110 km. The trajectory was planned with the newly developed optNEAR tool and validated with real time data. This article shows the results of the conjunction operation, from planning to flight data.

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The solar power sail can generate sufficient electric power to drive the high specific ion engine in the outer planetary region by thin-film solar cells attached to the entire surface of the spin-type solar sail. This paper proposes the direct exploration of the outer planetary region using solar power sail-craft. The target is an unexplored D/P-type Jovian Trojan asteroid. A lander is separated from the solar power sail-craft to collect surface and underground samples of the Trojan asteroid and perform in-situ analysis. The lander delivers samples to the solar power sail-craft for sample return to Earth as optional goal. Scientific observations during the interplanetary cruise are also implemented.

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