To celebrating the 2nd anniversary of The Japan Society of Vacuum and Surface Science (JVSS), we will feature the surface of the earth and vacuum. Contributions include topics on our environment of the land and ocean, the altitude atmosphere, two Hayabusa space development reports and space weathering. There may be new tips for our study of surface vacuum from the large earth environment.
Soil is defined as a mixture of weathering products of rocks (sand, silt, and clay) and humus (or soil organic matter) derived from plant or animal. World soils are divided into 12 groups and their distribution is not uniform. Soil degradation includes soil acidification in humid region, salinization in arid regions, and loss of soil organic matter in both regions. Minimum tillage or optimized fallow systems can minimize loss of soil organic matter and improve soil fertility. Understanding of complex soil system is required for food supply and human survival.
Nutrients such as nitrogen compounds, which control the amount of phytoplankton near the ocean's surface, are mostly supplied by deep ocean circulation. In the western North Pacific subtropical area, the amount of nutrients supplied to the ocean's surface in this manner is extremely small, indicating the importance of nutrients sourced from the atmosphere instead. To better understand this process, we developed improved numerical models by combining an atmospheric regional chemical transport model (WRF-CMAQ) and a 3-D lower trophic-marine ecosystem model (NEMURO). Phytoplankton amount increases noticeably in low- to mid-latitude regions (subtropical areas) when atmospheric nitrogen deposition was considered. This indicates that the atmospheric nitrogen compounds emitted from East Asia are likely to play an important role in increasing the amount of phytoplankton in the western North Pacific subtropical area.
A planetary atmosphere is the gaseous layer that divides the planetary surface and surrounding space. Although the Earth's atmosphere occupies a tiny fraction of the total Earth's mass, it plays an essential role to make the Earth's surface environment circulating liquid-water that is thought to be the most fundamental condition for the emergence and evolution of the terrestrial life organisms. The vertical structure of Earth's atmosphere from the Earth's surface to the uppermost region that merges into space is strongly influenced by interactions with space.
Changes in the global environment according to global warming in recent years are diverse and occur throughout the earth. Especially, the cryosphere region is sensitive to such fluctuations. This paper outlines the facts and situations observed by remote sensing in the cryosphere environment that is vulnerable to such environmental changes.
The microwave discharge plasma sources contributed to the reciprocating powered flight between Earth and the asteroids as the main propulsion system of the Hayabusa and Hayabusa2 asteroid explorers, and showed its high performance. The electron cyclotron resonance discharge only heats the electrons and does not induce ion sputtering damage. The reasons of high performance and long life are derived and proved theoretically, experimentally, and in practical use in space. In addition to further space applications, efforts are also being made for industrial applications.
Hayabusa2 explored a near-Earth C-type asteroid (162173) Ryugu for 17 months (June 2018–November 2019) including two landing operations for sample collection. Ryugu has a top shape with an equatorial ridge, and its bulk density of 1.19±0.03 g cm－3 suggests that Ryugu is a rubble-pile body with a large macro-porosity of ∼50–60%. The surface has a very low geometric albedo (∼0.02), darker than most of meteorite samples, and shows a weak but ubiquitous 2.72-µm absorption feature of hydrous minerals. The surface samples will be delivered to the Earth at the end of 2020. Detailed analysis of Ryugu samples will reveal the history of Ryugu and the Solar System from the beginning to the present.
High-energy particles and ions such as micro meteorites and solar wind are falling on the surface of an airless body, and space weathering that alters the surface material is occurring. Space weathering appears mainly as a change in optical properties. The mechanism was revealed by returned samples from an asteroid and moon. Research on space weathering has been progressing by simulation experiments for reproducing space weathering. In this paper, we will summarize what has been clarified so far, and look forward to future space weathering research.