Between 2.4 and 0.6 Gy ago, our planet underwent several episodes of global glaciations, including the Snowball Earth case that ended 635 My ago.
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![The green-to-red intensity ratio of [O I] (G/R) in 3I (filled circle), compared with measurements for a sample of Solar System comets: Jupiter-family comets (JFCs; open triangles), Oort Cloud comets (OCCs; open squares), and Halley-type comets (HTCs; crosses) from A. Decock et al. (2013); A. McKay et al. (2015); Y. Shinnaka & H. Kawakita (2016); Y. Shinnaka et al. (2020), as well as C/2016 R2 from C. Opitom et al. (2019) and 2I/Borisov from C. Opitom et al. (2021). -- astro-ph.GA](https://astrobiology.newspackstaging.com/wp-content/uploads/2026/03/A-post-perihelion-constraint.png)