Examination of Japanese Project to Study Martian Atmospheric Escape

The atmospheric escape from Mars is considered to be closely associated with the evolution of the Martian atmosphere as well as the existence of the water on Mars. We are now investigating a project to study the global feature and the physical process of the atmospheric escape from Mars. The goal of the project is to give an answer to the question, 'How carbon dioxide and water escape or disappear in the process of Martian atmospheric evolution?'. This project is expected to consist of two orbiters; one of the orbiters is aimed to make in-situ observation of plasma and thin atmosphere at about 100 km altitude, and the other is for the atmospheric imaging and solar-wind monitor. We are planning to make simultaneous observation of the atmospheric escape by the interaction with the solar wind using in-situ measurement orbiter and remote-sensing one. Two orbiters configuration will allow us to make a significant progress after MAVEN, by observing both global and detailed properties simultaneously, as well as the response to the solar wind. The latter is particularly important to suppose the atmospheric escape in ancient days. We have examined the quantitative measurement targets to fully understand the Martian atmospheric escape. At the same time, the sorts and performance of scientific instruments on these orbiters have been examined. We are now investigating the preliminary spacecraft design, orbit design and mission plan to achieve the scientific goal. Currently the working group mainly consists of Japanese scientists and the activity is supported by JAXA. Meanwhile the international collaboration is considered to be essential to realize this project, so we welcome the contributions by scientists outside Japan.