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Trending science: Three finalists vie to become concept for next ESA mission

Exoplanets, plasma physics and the X-ray Universe have been announced as the three finalist topics for the European Space Agency’s next medium-class mission.

Although the European Space Agency’s (ESA) next medium-class mission will not be launched until 2025, the agency has already whittled down the mission topic to three candidates: the Atmospheric Remote-Sensing Infrared Exoplanet Large-survey (Ariel), the Turbulence Heating ObserveR (Thor) and the X-ray Imaging Polarimetry Explorer (Xipe). One of these three concepts – which focus respectively on Exoplanets, plasma physics and the X-ray Universe – will be studied during the M4 mission, so called because it is the fourth of its kind in the ESA’s Cosmic Vision science programme. According to Alvaro Giménez, ESA Director of Science and Robotic Exploration, these candidates ‘offer the chance to tackle some of the major outstanding scientific questions about our place in the Universe.’ Professor Giménez added, ‘The selection of these three exciting mission concepts for study is an important step in the continuation of ESA’s long-term presence in space.’ Professor Giménez selected the three concepts from among 27 proposals following the recommendation by a peer review committee. The three candidates each represent very different missions for the ESA. If selected for the 2025 launch, the UK-led Ariel project would analyse the atmospheres of around 500 planets orbiting close to nearby stars, to determine their chemical composition and physical conditions. According to the ESA, the results would help scientists better understand planet formation, putting our own Solar System in context. Thor, which reports is run by a scientific consortium headquartered in Sweden, would address a fundamental problem in space plasma physics concerned with the heating of plasma and the subsequent dissipation of energy. Planned to orbit Earth, its studies would include the interaction of the solar wind with Earth’s magnetic field. The ESA says that the investigation would shed light on the underlying physical mechanisms of plasma behaviour under turbulent conditions, in order to understand a key interaction between planets and their host stars. Finally Xipe would study X-ray emissions from high-energy sources such as supernovas, galaxy jets, black holes and neutron stars, to discover more about the behaviour of matter under extreme conditions. It would be the first observatory sensitive enough to make high-resolution measurements of the polarisation of these sources, opening a new window into the high-energy Universe, according to the ESA. It will be several years before we know which space questions the mission will address. In order to arrive at a final decision, a study period will now begin in which the three teams receive funding to develop their concepts before one mission is selected. According to Science magazine, the winning mission will get a budget up to EUR 450 million. The ESA’s first three medium-class missions under the Cosmic Vision programme – Solar Orbiter, Euclid, and PLATO – are scheduled for launch in 2018, 2020 and 2024 respectively. For further information, please visit:


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