More spectral sleuthing attempted at ATLAS:
Astrophysics > Earth and Planetary Astrophysics arxiv.org/abs/2509.26053
[Submitted on 30 Sep 2025]
Hutsemékers, D. Manfroid, J. Jehin, E. et al. Extreme NiI/FeI abundance ratio in the coma of the interstellar comet 3I/ATLAS
As I’ve mentioned before, nickel is found in comets. Not because comets are particularly nickel-rich, but because nickel has spectral emission lines in the visible range. We can thus see nickel in common telescopes and instruments- a “visibility bias”. Regardless of why we are seeing it… we are seeing it, which makes nickel content a tracer element in these bodies. Here, Hutsemékers et al. report their measurements of nickel in 3I/ATLAS (as gauged relative to iron, a common and fairly stable mineral). At first, nickel appears rich, simply because iron was poor- for whatever reason, the comet was not showing iron emissions while in the outer Main Belt. The authors admit that, as ATLAS closes with the Sun and leaves the Belt, iron activity and spectral emissions have started to rise. (…”suggesting that comet 3I could soon become indistinguishable from solar system comets“.) We’ll see if later spectroscopy (particularly, by corroborating researchers) continues this trend as ATLAS continues inwards.