3I/ATLASEvidence
Evidence · 3I/ATLAS
Methane D/H the highest ever measured
Methane in 3I has a D/H ratio of 3.33 ± 0.31 per cent, 14 ± 2 times that of comet 67P and the highest methane D/H measured anywhere.
What it means
Key questionWhat is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?
No answer ahead yet
Openunchanged
Answer this evidence bears onAn icy body from a cold, metal-poor disc around an old star
Supports6 for, none against
Still possibleunchanged
What it implies
- A second molecule carries the same cold-formation signature as the water.For the key question: What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?
Next steps 2
1
Compare gas lost with crust depth
Could shiftFair odds~20 h
11score
Details
Use the compiled production rates (Frincke and Seligman's table) to date when more than 20 m of surface had gone, and check whether the composition changed then. A change at that point favours the crust; a change well before or after weakens it.
2
Test whether a cosmic-ray crust can raise D/H to 1 per cent
Could shiftFair odds~30 h
8score
Details
Run the cosmic-ray processing model forward to predict how much a 20-m processed crust changes water D/H and 12C/13C. If processing cannot reach the measured ratios, the birthplace reading is strengthened; if it can, the isotopes no longer date the body.
Ranked by how likely each is to move the key question, for the time it takes
Sources 2
Cite it
Mysteries Department. (2026). Methane D/H the highest ever measured [Evidence EVD0DFQ3SR2JMMK]. https://mysteriesdept.com/r/EVD0DFQ3SR2JMMK
@misc{mysteriesdept_evd0dfq3sr2jmmk,
title = {Methane D/H the highest ever measured},
author = {{Mysteries Department}},
year = {2026},
note = {Evidence, catalog key EVD0DFQ3SR2JMMK},
url = {https://mysteriesdept.com/r/EVD0DFQ3SR2JMMK}
}