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The Imaging Ultraviolet Spectrograph (IUVS) is one of nine science instruments aboard the Mars Atmosphere and Volatile and EvolutioN (MAVEN) spacecraft. MAVEN, launched in November 18, 2013 and arriving at Mars in September 2014, is designed to explore the planet's upper atmosphere and ionosphere and examine their interaction with the solar wind and solar ultraviolet radiation. IUVS is one of the most powerful spectrographs sent to another planet, with several key capabilities: (1) separate Far-UV & Mid-UV channels for stray light control, (2) a high resolution echelle mode to resolve deuterium and hydrogen emission, (3) internal instrument pointing and scanning capabilities to allow complete mapping and nearly-continuous operation, and (4) optimization for airglow studies. [ABSTRACT FROM AUTHOR]

Highlights • First detection of cloud top ozone in Venus atmosphere (about 1000 times less than Earth). • Ozone presence is restricted to high latitudes (polewards of 50°) in both hemispheres. • Measurements are qualitatively supported by our 3D photochemical model. Abstract After the first sporadic detections of an ozone (O 3) nighttime layer in the 90–100 km altitude range (Montmessin et al., 2011), we report here the discovery of another, permanent ozone layer on Venus, restricted to high latitudes (polewards of 50° both N and S) and located at the upper cloud level near 70 km. This detection was performed during a reanalysis of the whole SPICAV-UV nadir dataset through UV absorption near 250 nm in the backscattered solar light. The O 3 volume mixing ratio peaks in the 10–20 ppbv range, yielding observable column densities in the 0.1–0.5 Dobson units (DU), comparable to nominal values on Mars but much smaller than for Earth (∼ 300 DU). These measurements are supported by our 3D-photochemical model coupled with the LMD-IPSL GCM (Lebonnois et al., 2010), which indicates that the ozone layer identified by SPICAV results from downward transport of O 2 (∼ 50 ppmv) molecules over the poles by the mean meridional circulation. Our findings do not contradict previous upper limits (< 2 ppmv) based on O 2 measurements (Mills, 1999), since they were restricted to lower latitudes only. [ABSTRACT FROM AUTHOR]