Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet's birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25-7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and welldefined planet sample within its 4-year mission lifetime. Transit, eclipse and phasecurve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10-100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H 2 O, CO 2 , CH 4 NH 3 , HCN, H 2 S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performedusing conservative estimates of mission performance and a

Juno swoops around giant Jupiter Jupiter is the largest and most massive planet in our solar system. NASA's Juno spacecraft arrived at Jupiter on 4 July 2016 and made its first close pass on 27 August 2016. Bolton et al. present results from Juno's flight just above the cloud tops, including images of weather in the polar regions and measurements of the magnetic and gravitational fields. Juno also used microwaves to peer below the visible surface, spotting gas welling up from the deep interior. Connerney et al. measured Jupiter's aurorae and plasma environment, both as Juno approached the planet and during its first close orbit. Science , this issue p. 821 , p. 826

Published in: ScienceLink to article, DOI: 10.1126/science.aam5928 Publication date: 2017 Document VersionPeer reviewed version Link back to DTU Orbit Citation (APA): Connerney, J. E. P., Adriani, A., Allegrini, F., Bagenal, F., Bolton, S. J., Bonfond, B., ... Waite, J. (2017). Jupiter's magnetosphere and aurorae observed by the Juno spacecraft during its first polar orbits. Science, 356(6340) Abstract:The Juno spacecraft acquired direct observations of the Jovian magnetosphere and auroral emissions from a vantage point above the poles. Juno's capture orbit spanned the Jovian magnetosphere from bow shock to the planet, providing magnetic field, charged particle, and wave phenomena context for Juno's passage over the poles and traverse of Jupiter's hazardous inner radiation belts. Juno's energetic particle and plasma detectors measured electrons precipitating in the polar regions, exciting intense aurorae, observed simultaneously by the ultraviolet and infrared imaging spectrographs. Juno transited beneath the most intense parts of the radiation belts, passed ~4,000 kilometers above the cloudtops at closest approach, well inside the Jovian rings, and recorded the electrical signatures of high velocity impacts with small particles as it traversed the equator.One Sentence Summary: Juno's instruments provide complete polar maps of Jovian UV aurorae, spatially resolved images of the IR southern aurorae, and in-situ direct measurements of precipitating charged particle populations exciting the aurora. only one bow shock upon approach suggests that the magnetosphere was expanding in size, a conclusion bolstered by the multiple BS encounters experienced outbound during the 53.5 day capture orbit at radial distances of 92-112 Rj before apojove on DOY 213 (~113 Rj), and at distances of 102-108 Rj thereafter . Apojove during the 53.5day orbits occurred at a radial distance of ~113 Rj, so Juno resides at distances of >92 Rj for little more than half of its orbital period (~29 days). Thus on the first two orbits, Juno encountered the MP boundary a great many times at radial distances of ~81-113 Rj.Juno's traverse through the well-ordered portion of the Jovian magnetosphere is illustrated in The magnetic field observed in the previously unexplored region close to the planet (radius<1.3Rj) was dramatically different from that predicted by existing spherical harmonic models, revealing a planetary magnetic field rich in spatial variation, possibly due to a relatively large dynamo radius [1]. Perhaps the most perplexing observation was one that was missing: the expected magnetic signature of intense field aligned currents (Birkeland currents) associated with the main aurora. We did not identify large magnetic perturbations associated with Juno's traverse of field lines rooted in the main auroral oval (supplementary material).Juno's Waves instrument made observations of radio and plasma wave phenomena throughout the first perijove ( Figure 2). These observations were obtained at low altitudes whilst crossing magnetic field lines...