| A large number of hydrated minerals have been found on the surface of Mars by orbital remote sensing and in-situ exploration missions,providing strong evidence that water once existed on Mars.Hydrated sulfate is a typical evaporite mineral,and its formation is usually related to acidic water activities.Therefore,it is of great significance for the study of the changes of acid,alkalinity,water environment,temperature and humidity on the surface of Mars.On Mars,there is an internal layered deposit(ILD)formation which consists of bedded light-toned materials,usually containing a large amount of hydrated sulfate outcrops,and the current formation mechanisms of ILDs still debated.The classification and stratigraphic distribution of hydrated minerals are ambiguous in remote sensing,and it is also difficult to interpret mixed spectra with other minerals.China's upcoming 2020 Mars mission will be equipped with a Mars mineral spectrometer,and the pre-study work also needs to be expanded.This paper focused on several hydrated sulfates on Mars(including hydroxylated ferric sulfate,jarosite,szomolnokite,kieserite,etc.),and studies them by remote sensing and laboratory.First introduced the remote sensing data used in the paper,and the principle of recognition hydrated minerals with remote sensing in the visible near infrared spectrum,and introduced the methods of process remote sensing data.Then,we selectied the research area where hydrated sulfate on Mars had outcroped,and combined with laboratory samples with mix simulation work.Specific work is as follows:(1)There is a close relationship between the ILD and the water-bearing ferric sulfate on Mars.In this paper,two typical regions-Ophir chamsa and Aureum Chaos depression which near Valles Marineris were selected.Image data with different resolution,DEM data and CRISM hyperspectral data were respectively downloaded for processing and analysis.Ophir chasma's slope changed a lot,had a strong eroded surface,a large number of hydrated minerals covered the light-tone of wall and floor area.The main types of monohydrated sulfate and ferric oxide,which had a co-existence relationship with a small amount of polyhydrated sulfate,jarosite,hydrated silica minerals formed after the chasma.Aureum Chaos area is mainly composed of chaotic terrain,and the surface is usually smooth.Large scale monohydrate sulfate minerals are identified in the highlight unit,and are distributed in layers with polyhydrate sulfate,hydroxylated ferric sulfate,phyllosilicate and other minerals.In addition,there are a large number of light-toned bright materials with neutral spectral in this area.However,in this paper,mineral mapping and DEM data analysis were used to conclude that there was no lake or volcanism mode happened in either area,and it could be related to ground water activity.Among them,Ophir chasma has a valley-like landform and steep slope,and its water-bearing minerals may formed by the flow and infiltration of groundwater,while Aureum Chaos is more likely to happened with short-term water activities,such as evaporation,fog and rainfall.(2)Through the remote sensing detection's result,hydrated sulfate minerals on Mars often exist mixed phenomenon.We first synthesized the szomolnokite ferric sulfate,szomolnokite,kieserite and rozenite sample's laboratory pure phase,then Raman spectra and the ASD visible near infrared spectra characterization on them was carried out,and the relationship between spectral absorption depth parameter and the mass fraction were fitted,found that there is a certain linear relationship.Finally,combined the spectral parameter method and remote sensing data,the result of mixing experiment was carried out on the CRISM data,and the application of the experiment in remote sensing detection was realized. |
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