Early Mars volcanic sulfur storage in the cryosphere and formation of transient SO2-rich atmospheres during the Hesperian

In a previous paper (Chassefi\`ere et al., Icarus 223, 878-891, 2013), we have shown that most volcanic sulfur released to early Mars atmosphere could have been trapped in the cryosphere under the form of CO2-SO2 clathrates. Huge amounts of sulfur, up to the equivalent of a ~1 bar atmosphere of SO2, would have been stored in the Noachian cryosphere, then massively released to the atmosphere during Hesperian due to rapidly decreasing CO2 pressure. It would have resulted in the formation of the large sulfate deposits observed mainly in Hesperian terrains, whereas no or little sulfates are found at the Noachian. In the present paper, we first clarify some aspects of our previous work. We discuss the possibility of a smaller cooling effect of sulfur particles, or even of a net warming effect. We point out the fact that CO2-SO2 clathrates formed through a progressive enrichment of a preexisting reservoir of CO2 clathrates and discuss processes potentially involved in the slow formation of a SO2-rich upper cryosphere. We show that episodes of sudden destabilization at the Hesperian may generate 1000 ppmv of SO2 in the atmosphere and contribute to maintaining the surface temperature above the water freezing point.Comment: 15 pages, 1 figur

CO

Most sulfate minerals discovered on Mars are dated no earlier than the Hesperian. We showed, using a 1-D radiative-convective-photochemical model, that clathrate formation during the Noachian would have buffered the atmospheric CO2 pressure of early Mars at ~2 bar and maintained a global average surface temperature ~230 K. Because clathrates trap SO2 more favorably than CO2, all volcanically outgassed sulfur would have been trapped in Noachian Mars cryosphere, preventing a significant formation of sulfate minerals during the Noachian and inhibiting carbonates from forming at the surface in acidic water resulting from the local melting of the SO2- rich cryosphere. The massive formation of sulfate minerals at the surface of Mars during the Hesperian could be the consequence of a drop of the CO2 pressure below a 2-bar threshold value at the late Noachian-Hesperian transition, which would have released sulfur gases into the atmosphere from both the Noachian sulfur-rich cryosphere and still active Tharsis volcanism. Our hypothesis could allow to explain the formation of chaotic terrains and outflow channels, and the occurrence of episodic warm episodes facilitated by the release of SO2 to the atmosphere. These episodes could explain the formation of valley networks and the degradation of impact craters, but remain to be confirmed by further modeling

CO 2

Most sulfate minerals discovered on Mars are dated no earlier than the Hesperian. We showed, using a 1-D radiative-convective-photochemical model, that clathrate formation during the Noachian would have buffered the atmospheric CO2 pressure of early Mars at ~2 bar and maintained a global average surface temperature ~230 K. Because clathrates trap SO2 more favorably than CO2, all volcanically outgassed sulfur would have been trapped in Noachian Mars cryosphere, preventing a significant formation of sulfate minerals during the Noachian and inhibiting carbonates from forming at the surface in acidic water resulting from the local melting of the SO2- rich cryosphere. The massive formation of sulfate minerals at the surface of Mars during the Hesperian could be the consequence of a drop of the CO2 pressure below a 2-bar threshold value at the late Noachian-Hesperian transition, which would have released sulfur gases into the atmosphere from both the Noachian sulfur-rich cryosphere and still active Tharsis volcanism. Our hypothesis could allow to explain the formation of chaotic terrains and outflow channels, and the occurrence of episodic warm episodes facilitated by the release of SO2 to the atmosphere. These episodes could explain the formation of valley networks and the degradation of impact craters, but remain to be confirmed by further modeling

Bridging the gap between benchtop testing and field conditions in flow assurance studies

E-Book - ISBN: 978-1-61399-571-6International audienceObjectives/Scope: The goal for any flow assurance study is to capture the thermo-hydraulic conditions in flowlines without having large scale flow facilities that closely represent the field. As such, benchtop testing must as best as possible reproduce the shear and dispersion of the phases encountered in flowlines. With the increasing need of laboratory testing for solid precipitation and production chemicals, coupled with reduced CAPEX and OPEX, it is critically important to have a robust benchtop testing system that give reliable and transferable data that can be used for field applications.Methods, Procedures, Process: While many benchtop tools are widespread (e.g., autoclave cells, rocking cells, cold fingers) and are used extensively by industry, there is still a significant gap in bridging the results from these lab scale devices to field conditions. One of the major concerns with the current testing rigs is the inability to reproduce the shear AND phases dispersion that are present in pipe flow and are a consequence of the multiphase flow conditions. To bridge the gap To bridge the gap between benchtop testing and filed conditions, we demonstrate how an innovative testing rig, called rock-flow cell, can be used to capture flow assurance issues (e.g., hydrate, wax, asphaltene, scale, corrosion, sand transport) under pseudo-flow conditions.Results, Observations, Conclusions: This system is superior to existing testing systems due to its ability to reproduce flow conditions that are typically found in actual production flowlines, such as, stratified flow, stratified wavy flow, and slug flow. In addition, the system is compact and inexpensive to build and operate, unlike flow loop systems, which are currently the only reliable testing rig with proper flow conditions.Novel/Additive Information: The rock-flow cell can be easily used for testing of chemicals (e.g., anti-agglomerants and kinetic inhibitors) for hydrate management, for assessing wax deposition of crude oils, for testing of scale precipitation, and for testing of sand transport; each of these flow assurance issues can be tested separated or combined as desired. Moreover, the rock-flow cell is also a suitable setup for testing of steady-state and transient (shut-in/restart) conditions typically encountered in flow assurance with proper account of liquid loading, water cut, and GOR