Revised upper limits for abundances of NH
3, HCN and HC 3N in the Martian atmosphere
Icarus 407 (2024)
Abstract:The Atmospheric Chemistry Suite (ACS) onboard the ExoMars Trace Gas Orbiter (TGO) spacecraft has been studying Mars' atmosphere since 2018. The sensitivity of the middle infrared channel (MIR) allows it to address many ardent topics and it is capable of improving and establishing upper limits for many trace species. In this work we present analysis of transmittance spectra in the 3332.5–3338.6 cm−1 range with 30,000 resolution (λ∕Δλ), covering absorptions lines of three nitrogen-bearing species: ammonia (NH3), hydrogen cyanide (HCN) and cyanoacetylene (HC3N). According to existing models, all of those are not expected to be present in a CO2-rich Martian atmosphere, but outgassing or unknown chemistry sources cannot be discounted. The upper limits of 14, 1.5 and 11 ppbv are obtained for NH3, HCN and HC3N from individual occultation measurements during the warm and dusty perihelion season of martian year 36. For the ammonia and hydrogen cyanide the upper limits are improved compared to previously published results. A search for cyanoacetylene on Mars is reported for the first time.
L’Ralph: A Visible/Infrared Spectral Imager for the Lucy Mission to the Trojans
Space Science Reviews 219:8 (2023)
Abstract:The Lucy Mission to the Trojan asteroids in Jupiter’s orbit carries an instrument named L’Ralph, a visible/near infrared multi-spectral imager and a short wavelength infrared hyperspectral imager. It is one of the core instruments on Lucy, NASA’s first mission to the Trojans. L’Ralph’s primary purpose is to map the surface geology and composition of these objects, but it will also be used to search for possible tenuous exospheres. It is compact, low mass (32.3 kg), power efficient (24.5 W), and robust with high sensitivity and excellent imaging. These characteristics, and its high degree of redundancy, make L’Ralph ideally suited to this long-duration multi-flyby reconnaissance mission.
Latitudinal variations in methane abundance, aerosol opacity and aerosol scattering efficiency in Neptune's atmosphere determined from VLT/MUSE
ArXiv 2310.13525 (2023)
The Temporal Brightening of Uranus' Northern Polar Hood From HST/WFC3 and HST/STIS Observations
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS American Geophysical Union (AGU) 128:10 (2023) ARTN e2023JE007904
Abstract:Hubble Space Telescope Wide-Field Camera 3 (HST/WFC3) observations spanning 2015 to 2021 confirm a brightening of Uranus' north polar hood feature with time. The vertical aerosol model of Irwin et al. (2023, https://doi.org/10.1038/s41550-023-02047-0) (IRW23), consisting of a deep haze layer based at ∼5 bar, a 1–2 bar haze layer, and an extended haze rising up from the 1–2 bar layer, was applied to retrievals on HST Space Telescope Imaging Spectrograph (STIS) (HST/STIS) observations (Sromovsky et al., 2014, 2019, https://doi.org/10.1016/j.icarus.2014.05.016, https://doi.org/10.1016/j.icarus.2018.06.026) revealing a reduction in cloud-top CH4 volume mixing ratio (VMR) (i.e., above the deep ∼5 bar haze) by an average of 0.0019 ± 0.0003 between 40–80◦N (∼10% average reduction) from 2012 to 2015. A combination of latitudinal retrievals on the HST/WFC3 and HST/STIS data sets, again employing the IRW23 model, reveal a temporal thickening of the 1–2 bar haze layer to be the main cause of the polar hood brightening, finding an average increase in integrated opacity of 1.09 ± 0.08 (∼33% increase) at 0.8 µm north of ∼45°N, concurrent with a decrease in the imaginary refractive index spectrum of the 1–2 bar haze layer north of ∼40°N and longwards of ∼0.7 µm. Small contributions to the brightening were found from a thickening of the deep aerosol layer, with an average increase in integrated opacity of 0.6 ± 0.1 (58% increase) north of 45°N between 2012 and 2015, and from the aforementioned decrease in CH4 VMR. Our results are consistent with the slowing of a stratospheric meridional circulation, exhibiting subsidence at the poles.
Jupiter Science Enabled by ESA's Jupiter Icy Moons Explorer.
Space science reviews Springer Nature 219:7 (2023) 53