Explosive volcanism on the surface of planet Mercury is visible through the pyroclastic deposits that surround morphologic features often identified as the vent. Those deposits are known as faculae. The understanding of explosive volcanism provides important information on Mercury's geological, thermal, and volcanic history. Observations by the MESSENGER spacecraft are used to analyze in detail the spectral properties of 14 selected faculae with the aim of understanding their chemical and physical properties. Scientific observations obtained by the MASCS instrument are particularly suitable for this task, although their observational and geometrical constraints limit definitive conclusions. Nonetheless, spectral properties in the visible, ultraviolet and near-infrared indicate that the selected faculae are probably larger than visible in images solely. Spectral parameters provide a means to isolate Mercury's pyroclastic deposits with respect to Mercury's average spectral behavior. The similar spectral behavior of the visible, ultraviolet and near-infrared domains suggests that the amount of mixing of pyroclastic materials with the underlying material, the differences in grain sizes between and inside the faculae, and the presence of opaque/mineral phases, could play significant roles in the spectral properties observed. Observations by the BepiColombo mission in nadir configuration covering a large range of phase angles will be highly complementary to the MESSENGER observations.
Plain Language SummaryThe presence of volcanism on Mercury has been confirmed from observations taken by the NASA MESSENGER mission in 2011. As on Earth, various styles of volcanism have been detected; explosive volcanism which involves a low volume of lava and high volume of gas, and effusive volcanism, which is richer in lava and poorer in gas. Using observations in the near-infrared and visible spectral domain, this analysis aims at better characterizing the physical and chemical properties of the deposits resulting from explosive volcanism. In this manuscript, it is shown that the scale of deposits resulting from explosive volcanism has been underestimated, which cascades to a potential underestimation of the quantity of gas present in the interior of Mercury through its history. Additionally, it is shown that the amount of mixing of pyroclastic materials with the underlying material, the differences in grain sizes between and inside the faculae, and the presence of opaque/mineral phases, could play significant roles in the spectral properties observed in near infrared and visible spectral domain. Unfortunately, the limitations in the measurements from MESSENGER complicate the exploration of physical and chemical properties. These issues will be better explored with the BepiColombo mission, the next mission to explore the surface of Mercury.
Informal settlements are home to the most socially and economically vulnerable people on the planet. In order to deliver effective economic and social aid, non-government organizations (NGOs), such as the United Nations Children's Fund (UNICEF), require detailed maps of the locations of informal settlements. However, data regarding informal and formal settlements is primarily unavailable and if available is often incomplete. This is due, in part, to the cost and complexity of gathering data on a large scale. To address these challenges, we, in this work, provide three contributions. 1) A brand new machine learning data-set, purposely developed for informal settlement detection. 2) We show that it is possible to detect informal settlements using freely available low-resolution (LR) data, in contrast to previous studies that use very-high resolution (VHR) * Both authors contributed equally to this research. satellite and aerial imagery, something that is cost-prohibitive for NGOs. 3) We demonstrate two effective classification schemes on our curated data set, one that is cost-efficient for NGOs and another that is cost-prohibitive for NGOs, but has additional utility. We integrate these schemes into a semi-automated pipeline that converts either a LR or VHR satellite image into a binary map that encodes the locations of informal settlements.
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