Martian volcanism:Current state of knowledge and known unknowns

Much has been discovered about volcanism on Mars over the past fifty years of space exploration. Previous reviews of these discoveries have generally focused on the volcanic constructs (e.g., Olympus Mons and the other volcanoes within the Tharsis and Elysium regions), the analysis of individual lava flows, and how volcanic activity on Mars has evolved over time. Here we focus on attributes of volcanology that have received less attention and build upon characteristics of terrestrial volcanoes to pose new questions to guide future analyses of their Martian equivalents either with existing data sets or with new types of measurements that need to be made. The remarkable lack of exposed dikes at eroded ancient volcanoes attests to an internal structure that is different from terrestrial equivalents. Enigmatic aspects of the origin of the ridged plains (commonly accepted to be volcanic but with few identifiable flow fronts and only rare vents), the style(s) of volcanism during the earliest period of Martian history (the Noachian), and the possible mode(s) of formation of the Medusae Fossae Formation are considered here. Martian meteorites have been dated and are volcanic, but they cannot be correlated with specific geographic areas, or the chronology of Mars derived from the number of superimposed impact craters. Some of these questions about Martian volcanism can be addressed with existing instrumentation, but further progress will most likely rely on the acquisition of new data sets such as high-resolution gravity data, the return of samples from known localities, the flight of a synthetic aperture imaging radar, penetrators sent to the Medusae Fossae Formation, and detailed in situ field observations of selected volcanic sites

Aeolian processes and landforms in the sub-Antarctic: preliminary observations from Marion Island

Sub-Antarctic Marion Island has a hyperoceanic climate, with cold and wet conditions and consistently strong wind velocities throughout the year. Recent observations recognized the increasing role of aeolian processes as a geomorphic agent, and this paper presents the first data for transport by aeolian processes on a sub-Antarctic island. Data were collected through an intensive and high-resolution measurement campaign at three study sites using Big Spring Number Eight sediment traps and surface sediment samplers in conjunction with an array of climatic and soil logger sensors. Observed aeolian landforms are megaripples, and the data suggest that aeolian processes are also modifying solifluction landforms. The sediment traps and sediment samplers collected wind-blown scoria at all three study sites, and the annual (horizontal) aeolian sediment flux extrapolated from this preliminary data is estimated at 0.36–3.85 kg cm−2 y−1. Importantly, plant material of various species was trapped during the study that suggests the efficiency of wind for the dispersal of plants in this sub-Antarctic environment may be underestimated. This paper advocates long-term monitoring of aeolian processes and that the link between aeolian processes and synoptic climate must be established. Furthermore, wind as a means to disperse genetic material on Marion Island should be investigated

Numerical modeling of wind-blown sand on Mars

Recent observation results show that sand ripples and dunes are movable like those on Earth under current Martian climate. And the aeolian process on Mars therefore is re-attracting the eyes of scientific researchers in different fields. In this paper, the spatial and temporal evolution of wind-blown sand on Mars is simulated by the large-eddy simulation method. The simulations are conducted under the conditions of both friction wind speed higher and lower than the “fluid threshold”, respectively. The fluid entrainment of the sand particles, the processes among saltation sand particles and sand bed, and the negative feedback of sand movement to flow field are considered. Our results show that the “overshoot” phenomenon also exists in the evolution of wind-blown sand on Mars both temporally and spatially; impact entrainment affects the sand transport rate on Mars when the wind speed is smaller or larger than the fluid threshold; and both the average saltation length and height are one order of magnitudes larger than those on Earth. Eventually, the formulas describing the sand transport rate, average saltation length and height on Mars are given, respectively