Colin F. Wilson

South-polar features on Venus similar to those near the north pole

Venus has no seasons, slow rotation and a very massive atmosphere, which is mainly carbon dioxide with clouds primarily of sulphuric acid droplets. Infrared observations by previous missions to Venus revealed a bright ‘dipole’ feature surrounded by a cold ‘collar’ at its north pole. The polar dipole is a ‘double-eye’ feature at the centre of a vast vortex that rotates around the pole, and is possibly associated with rapid downwelling. The polar cold collar is a wide, shallow river of cold air that circulates around the polar vortex. One outstanding question has been whether the global circulation was symmetric, such that a dipole feature existed at the south pole. Here we report observations of Venus’ south-polar region, where we have seen clouds with morphology much like those around the north pole, but rotating somewhat faster than the northern dipole. The vortex may extend down to the lower cloud layers that lie at about 50 km height and perhaps deeper. The spectroscopic properties of the clouds around the south pole are compatible with a sulphuric acid composition.

Venus’s Southern Polar Vortex Reveals Precessing Circulation

Observations with the Venus Express Orbiter reveal complex polar atmospheric dynamics. Initial images of Venus’s south pole by the Venus Express mission have shown the presence of a bright, highly variable vortex, similar to that at the planet’s north pole. Using high-resolution infrared measurements of polar winds from the Venus Express Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, we show the vortex to have a constantly varying internal structure, with a center of rotation displaced from the geographic south pole by ~3 degrees of latitude and that drifts around the pole with a period of 5 to 10 Earth days. This is indicative of a nonsymmetric and varying precession of the polar atmospheric circulation with respect to the planetary axis.

Tropospheric carbon monoxide concentrations and variability on Venus from Venus Express/VIRTIS-M observations

We present nightside observations of tropospheric carbon monoxide in the southern hemisphere near the 35 km height level, the first from Venus Express/Visible and Infrared Thermal Imaging Spectrometer (VIRTIS)-M-IR. VIRTIS-M data from 2.18 to 2.50 μm, with a spectral resolution of 10 nm, were used in the analysis. Spectra were binned, with widths ranging from 5 to 30 spatial pixels, to increase the signal-to-noise ratio, while at the same time reducing the total number of retrievals required for complete spatial coverage. We calculate the mean abundance for carbon monoxide at the equator to be 23 ± 2 ppm. The CO concentration increases toward the poles, peaking at a latitude of approximately 60°S, with a mean value of 32 ± 2 ppm. This 40% equator-to-pole increase is consistent with the values found by Collard et al. (1993) from Galileo/NIMS observations. Observations suggest an overturning in this CO gradient past 60°S, declining to abundances seen in the midlatitudes. Zonal variability in this peak value has also been measured, varying on the order of 10% (~3 ppm) at different longitudes on a latitude circle. The zonal variability of the CO abundance has possible implications for the lifetime of CO and its dynamics in the troposphere. This work has definitively established a distribution of tropospheric CO, which is consistent with a Hadley cell circulation, and placed limits on the latitudinal extent of the cell.

Simulating weathering of basalt on Mars and Earth by thermal cycling

Physical weathering induced by heating and cooling may cause rock breakdown on Mars and Earth. We report results from parallel weathering simulations on basalt blocks exposed to diurnal cycles representing Mars-like (two simulation runs from −55 to +20 oC and −75 to +10 oC, 1–100% relative humidity, 4–8 mbar pressure, CO_2 atmosphere) and hot arid Earth (23–72o C, 30–100% relative humidity) conditions. Under Earth conditions, thermally pre-stressed blocks showed measurable strength declines, whilst salt pre-treated blocks showed strength gains. Under Mars-like conditions, pre-stressed blocks recorded greater or similar strength declines and salt pre-treated blocks showed more muted strength declines than under Earth conditions. The results imply that on Earth and Mars diurnal cycling of temperature alone can cause deterioration of basalt with a pre-existing stress history. The type of stress history is important, with salt pre-treatment affecting the response of thermally pre-stressed blocks under both Earth and Mars conditions.

Performance characteristics of the PAW instrumentation on Beagle 2 (the astrobiology lander on ESA's Mars Express Mission)

The performance of the PAW instrumentation on the 60kg Beagle 2 lander for ESA’s 2003 Mars Express mission will be described. Beagle 2 will search for organic material on and below the surface of Mars in addition to a study of the inorganic chemistry and mineralogy of the landing site. The lander will utilize acquisition and preparation tools to obtain samples from below the surface, and both under and inside rocks. In situ analysis will include examination of samples with an optical microscope, Mossbauer and fluorescent X-ray spectrometers. Extracted samples will be returned to the lander for analysis, in particular a search for organics and a measurement of their isotopic composition. The PAW experiment performance data will be described along with the status of the project.

The ExoMars DREAMS scientific data archive

DREAMS (Dust Characterisation, Risk Assessment, and Environment Analyser on the Martian Surface) is a payload accommodated on the Schiaparelli Entry and Descent Module (EDM) of ExoMars 2016, the ESA – Roscosmos mission to Mars successfully launched on 14 March 2016. The DREAMS data will be archived and distributed to the scientific community through the ESA’s Planetary Science Archive (PSA). All data shall be compliant with NASA’s Planetary Data System (PDS4) standards for formatting and labelling files. This paper summarizes the format and content of the DREAMS data products and associated metadata. The pipeline to convert the raw telemetries to the final products for the archive is sketched as well.

Venus Express: Lessons from 8 years of science operations

Nomenclature ASPERA= Analyzer of Space Plasma and Energetic Atoms EDF = Experiment Definition Files EPS = Experiment Planning System ESA = European Space Agency ESAC = European Space Astronomy Centre located near Madrid, Spain ESOC = European Space Operations Centre located near Darmstadt, Germany EVF = Event Files FOV = Field Of View HGA = High Gain Antenna ITL = instrument timeline JPL = Jet Propulsion Laboratory MAG = Venus Express Magnetometer MAPPS = Mapping and Planning Software NASA = National Aeronautics and Space Agency (USA) OCM = Orbital Correction Maneuver OFPM = Operations Files Push Mechanism ORFA = Operations Request File Acknowledger PFS = Planetary Fourier Spectrometer PTR = pointing request SAP = Science Activity Plan SPICAV/SOIR = Ultraviolet and Infrared Atmospheric Spectrometer VCO = Venus Climate Orbiter (Japan), a.k.a Akatsuki VeRa = Venus Radio Science Experiment VEX = Venus Express VIRTIS = Visible/Ultraviolet/Near-infrared Mapping Spectrometer VMC = Venus Monitoring Camera VMOC = Venus Express Mission Operations Centre VOI = Venus orbit insertion VSOC = Venus Express Science Operations Centre

Characterizing atmospheric waves on Venus, Earth, and Mars

Atmospheric Waves Workshop; Noordwijk, Netherlands, 9–10 November 2011 Experts in observations and modeling of atmospheric waves from the Earth and planetary atmospheric science communities came together at a November 2011 workshop held at the European Space Agencys (ESA) European Space Research and Technology Centre ( ESTEC) site in the Netherlands to discuss the nature of waves observed in Venuss atmosphere and their comparison to those on Earth and Mars. ESAs Venus Express (VEx) satellite and ground-based observers find atmospheric waves at many scales. Migrating solar tides and other planetary- scale waves are observed in cloud- tracking wind vectors and temperature fields. Mesoscale gravity waves (GWs) can also be seen at a variety of levels from the cloud base up to the thermosphere, evident in imagery and in vertical profiles of temperature, density, and aerosol abundance. This workshop focused particularly on GWs, as their role in the atmospheric circulation is still poorly understood.