Reflectance and Emissivity spectra of graphite as potential darkening agent for Mercury from the UV to the TIR and its Comparison to Remote Sensing Measurements from MESSENGER and Mertis on BepiColombo

Kurzfassung

For long time Mercury was considered a planet very similar to the Moon. Both are small rocky bodies in the inner solar system with thin exospheres and no large scale traces of recent geological activity. However Mercury’s surface reflects much less sunlight than the Moon. Trying to explain the reasons for this difference, significant abundances of iron and titanium (and their oxides) were proposed for the Hermean surface. But the NASA MESSENGER instruments found only small abundances of iron, confirming earlier ground-based spectroscopy observations, and virtually no titanium. Therefore neither of the elements can account for this diversity. New analysis of MESSENGER data acquired for the darkest regions of Mercury’s surface suggest that the unknown darkening material could be carbon, in particular as the mineral graphite [1] whose abundance in the darker regions is predicted to be 1 to 3 wt% higher than the surroundings.