Geologic Analysis of the Near-Infrared Images of the Surface Taken by the Venus Monitoring Camera, Venus Express

English Abstract:

We analyzed night-time near-infrared (NIR) thermal emission images of the Venus surface obtained with the 1-micron channel of the Venus Monitoring Camera onboard Venus Express. There were several directions of our analysis. (1) We studied if tessera terrain has the different NIR emissivity (and thus might have different mineralogic composition) in comparison to the surrounding basaltic plains. Our analysis showed that NIR emissivity of tessera surface material is by 15–35% lower than that of relatively fresh supposedly basaltic lavas of plains. This is consistent with hypothesis that the tessera material is not basaltic andmaybe felsic. (2) We found that the surface materials of plains around Chimon-mana tessera are very variegated in their 1-micron emissivity, probably reflecting differences in degree of their chemical weathering. (3) We also found a possible decrease of NIR emissivity at the top of Tuulikki Mons volcano which may be due to different, possibly more felsic composition of volcanic products on the volcano summit. (4) We have also foundseveral transient bright spots which suggest ongoing extrusions of lava flows causing significant elevation of surface temperatures. These bright spots occur in Ganiki Chasma, an extensive linear rift zone known to represent a stratigraphically youngest tectonic activity. The very strong spatial correlation of the transient bright spots and the Ganiki rift zone boundaries and their similarity to locations of rift-associated volcanism on Earth, provide strong evidence for their volcanic origin