The Apparent Absence of Kilometer‐Sized Pyroclastic Volcanoes on Mercury: Are We Looking Right?

Abstract

Spacecraft data reveal that volcanism was active on Mercury. Evidence of large‐volume effusive and smaller‐scale explosive eruptions has been detected. However, only large (>~15 km) volcanic features or vents have been found so far, despite abundant high‐resolution imagery. On other volcanic planets, the size of volcanoes is anticorrelated with their frequency; small volcanoes are much more numerous than large ones. Here we present results of a numerical model that predicts the shapes of ballistically emplaced volcanic edifices and hence can explain the lack of kilometer‐sized constructional explosive volcanoes on the surface of Mercury. We find that due to the absence of the atmosphere, particles are spread on this planet over a larger area than is typical for Earth or Mars. Erupted volumes are likely insufficient to build edifices with slope angles that enable their easy recognition with currently available data or that could survive destruction by subsequent impact bombardment.

Spectral Properties and Physical Extent of Pyroclastic Deposits on Mercury: Variability Within Selected Deposits and Implications for Explosive Volcanism

“…Therefore, the analysis of faculae requires utmost care, specifically when those spectral properties (i.e., spectral slope variations) are changing at local scale. Pyroclastic deposits are quasi-radial deposits thought to be created via the ballistic emplacement of rock and melt fragments from a central vent in absence of a substantial atmosphere and atmospheric circulation (Brož et al, 2018). The distance to which a pyroclast is emplaced depends on the energy by which it was propelled from the vent, and the angle of dispersion from the volcanic conduit.…”

Recent Dark Pyroclastic Deposits on Mercury

“…(2) parameters defining LRM were based on the spectral characteristics of the entire planet, and the threshold values were subjectively determined (Peplowski et al, 2016;Klima et al, 2018); (3) the thickness of mercurian pyroclastic deposits decreases rapidly outward (Brož et al, 2018), so spectra for the diffuse parts are affected by those of background materials (Besse et al, 2020). While the Case 2 pyroclastic deposit can be partly classified as LRM (Figure S13), a graphite absorption feature is basically invisible, except in the crater center that hosts the three pits and potential hollows (Figures 3c and 3d).…”

“…Compared to the quantified spectral parameters that defined LRM on Mercury (Klima et al, 2018), the two Kuiperian-aged dark pyroclastic deposits and LRM have similar reflectances and PC2, but only parts of the dark pyroclastics fit the definition of LRM, as the rest exhibit steeper spectral slopes than LRM (Figure S13). The redder spectra can be explained by a combination of three factors: (1) inherent compositional variations among patches of dark pyroclastics; (2) parameters defining LRM were based on the spectral characteristics of the entire planet, and the threshold values were subjectively determined (Peplowski et al, 2016;Klima et al, 2018); (3) the thickness of mercurian pyroclastic deposits decreases rapidly outward (Brož et al, 2018), so spectra for the diffuse parts are affected by those of background materials (Besse et al, 2020). While the Case 2 pyroclastic deposit can be partly classified as LRM (Figure S13), a graphite absorption feature is basically invisible, except in the crater center that hosts the three pits and potential hollows (Figures 3c and 3d).…”

Toksisitas Merkuri (Hg) pada struktur jaringan ikan

“…Kehadiran logam berat merkuri (Hg) di lingkungan dapat terjadi secara alamiah dan akibat dari aktivitas manusia (Brož et al, 2018;Chen et al, 2018;Zhang et al, 2019). Sumber pencemaran merkuri (Hg) berasal dari emulsi industri, pembakaran batu bara serta limbah ekstraksi mineral dalam pertambangan emas (Li et al, 2018;Spiegel et al, 2018;Zhang et al, 2018;Ma et al, 2019).…”