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Register a new userStatistical analysis of Curiosity data shows no evidence for a strong seasonal cycle of Martian methane
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Using Gaussian Process regression to analyze the Martian surface methane Tunable Laser Spectrometer (TLS) data reported by Webster (2018), we find that the TLS data, taken as a whole, are not statistically consistent with seasonal variability. The subset of data derived from an enrichment protocol of TLS, if considered in isolation, are equally consistent with either stochastic processes or periodic variability, but the latter does not favour seasonal variation.
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In this work we investigate the problem concerning the presence of additional bodies gravitationally bounded with the WASP-3 system. We present eight new transits of this planet and analyse all the photometric and radial velocity data published so far. We did not observe significant periodicities in the Fourier spectrum of the observed minus calculated (O-C) transit timing and radial velocity diagrams (the highest peak having false-alarm probabilities of 56 per cent and 31 per cent, respectively) or long-term trends. Combining all the available information, we conclude that the radial velocity and transit timing techniques exclude, at 99 per cent confidence limit, any perturber more massive than M gtrsim 100 M_Earth with periods up to 10 times the period of the inner planet. We also investigate the possible presence of an exomoon on this system and determined that considering the scatter of the O-C transit timing residuals a coplanar exomoon would likely produce detectable transits. This hypothesis is however apparently ruled out by observations conducted by other researchers. In case the orbit of the moon is not coplanar the accuracy of our transit timing and transit duration measurements prevents any significant statement. Interestingly, on the basis of our reanalysis of SOPHIE data we noted that WASP-3 passed from a less active (log R_hk=-4.95) to a more active (log R_hk=-4.8) state during the 3 yr monitoring period spanned by the observations. Despite no clear spot crossing has been reported for this system, this analysis claims for a more intensive monitoring of the activity level of this star in order to understand its impact on photometric and radial velocity measurements.
In the light of the recent announcement of the discovery of the potential biosignature phosphine in the atmosphere of Venus I present an independent reanalysis of the original JCMT data to assess the statistical reliability of the detection. Two line detection methods are explored, low order polynomial fits and higher order multiple polynomial fits. A non-parametric bootstrap analysis reveals that neither line detection method is able to recover a statistically significant detection. Similar to the results of other reanalyses of ALMA Venus spectra, the polynomial fitting process results in false positive detections in the JCMT spectrum. There is thus no significant evidence for phosphine absorption in the JCMT Venus spectra.
We present characterization of the planetary system architecture for V488 Per, the dustiest main sequence star known with a fractional infrared luminosity of ~16%. Far-infrared imaging photometry confirms the existence of an outer planetary system dust population with blackbody-fit temperature of ~130 K. Mid-infrared spectroscopy probing the previously-identified ~800 K inner planetary system dust population does not detect any obvious solid-state emission features, suggesting either large grain sizes that mute such emission and/or grain compositions dominated by species like amorphous carbon and metallic iron which do not produce such features. In the latter case, the presence of significant quantities of iron-rich material could be indicative of the active formation of a Mercury-like planet around V488 Per. In any event, the absence of solid-state emission features is very unusual among main sequence stars with copious amounts of warm orbiting dust particles; we know of no other such star whose mid-infrared spectrum lacks such features. Combined radial velocity monitoring and adaptive optics imaging find no evidence for stellar/sub-stellar companions within several hundred AU of V488 Per.
We investigate the feasibility and demonstrate the merits of using Mars Orbiter Laser Altimeter (MOLA) profiles to retrieve seasonal height variations of CO2 snow/ice cap in Mars polar areas by applying a co-registration strategy. We present a prototype analysis on the research region of [85.75{deg}S, 86.25{deg}S, 300{deg}E, 330{deg}E] that is located on the residual south polar cap. Our method comprises the recomputation of MOLA footprint coordinates with an updated Mars Global Surveyor (MGS) ephemeris and a revised Mars rotation model. The reprocessed MOLA dataset at the South Pole of Mars (poleward of 78{deg}S) is then self-registered to form a coherent reference digital terrain model (DTM). We co-register segments of reprocessed MOLA profiles to the self-registered MOLA reference DTM to obtain the temporal height differences at either footprints or cross-overs. Subsequently, a two-step Regional Pseudo Cross-over Adjustment (RPCA) procedure is proposed and applied to post-correct the aforementioned temporal height differences for a temporal systematic bias and other residual errors. These pseudo cross-overs are formed by profile pairs that do not necessarily intersect, but are connected through the underlaying DTM. Finally, CO2 snow/ice temporal height variation is obtained by median-filtering those post-corrected temporal height differences. The precision of the derived height change time series is ~4.9 cm. The peak-to-peak height variation is estimated to be ~2 m. In addition, a pronounced pit (transient height accumulation) of ~0.5 m in magnitude centered at Ls=210{deg} in southern spring is observed. The proposed method opens the possibility to map the seasonal CO2 snow/ice height variations at the entire North and South polar regions of Mars.
We extracted a Martian water-ice cloud climatology from OMEGA data covering 7 Martian years (MY 26-32). We derived two products, the Reversed Ice Cloud Index (ICIR) and the Percentage of Cloudy Pixels (PCP), indicating the mean cloud thickness and nebulosity over a regular grid (1{deg} longitude x 1{deg} latitude x 1{deg} Ls x 1 h Local Time). The ICIR has been shown to be a proxy of the water-ice column derived from the Mars Climate Database. The PCP confirms the location of the main cloud structures mapped with the ICIR, and gives a more accurate image of the cloud cover. We observed a denser cloud coverage over Hellas Planitia, Lunae Planum and over large volcanoes in the aphelion belt. For the first time, thanks to the fact that Mars Express is not in Sun-synchronous orbit, we can explore the cloud diurnal cycle at a given season by combining 7 years of observations. However, because of the eccentric orbit, the temporal coverage remains limited. Other limitations of the dataset are its small size, the difficult distinction between ice clouds and frosts, and the impact of surface albedo on data uncertainty. We could nevertheless study the diurnal cloud life cycle by averaging the data over larger regions: from specific topographic features (covering a few degrees in longitude and latitude) up to large climatic bands (all longitudes). We found that in the tropics around northern summer solstice, the diurnal thermal tide modulates the abundance of clouds, which is reduced around noon. At northern midlatitudes, clouds corresponding to the edge of the north polar hood are observed mainly in the morning and around noon during northern winter (Ls=260-30{deg}). Over Chryse Planitia, low lying morning fogs dissipate earlier and earlier in the afternoon during northern winter. Over Argyre, clouds are present over all daytime during two periods, around Ls = 30 and 160{deg}.
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