Speaker
Description
The middle atmosphere between about 80 km and more than 100 km altitude is well known for a layer of metal atoms like sodium, iron, nickel, calcium, etc. The metal layer is mostly formed by ablating meteoroids, which inject about 30 tons per day of cosmic material into the atmosphere. These metal atoms have been observed for decades, first by twilight spectrometry and later by resonance lidar. Thus, the natural variability and height distribution of most of these metals are well understood. Other species have rarely been observed so far because their natural abundances or backscatter cross-sections are very low. Until now, the anthropogenic contribution to the material entering the atmosphere from space, namely re-entering satellites, has been small compared to the natural source. But the composition of space debris is much different from that of meteoroids, with a higher fraction of, e.g., Al and Ni. Given the expected increase in space debris, this may alter the composition of the metal layers and enable the detection of elements that are so far invisible to ground-based lidars. We will give an overview of our plans for new and continuous observations of the mesospheric metal layer.
