3I/ATLASEvidence
Evidence · 3I/ATLAS
CO2-to-water ratio fell from 7.6 to about 0.1
The coma's CO2-to-water ratio fell from 7.6 ± 0.3 at 3.3 au inbound to about 0.1 near perihelion and stayed far below the inbound value at 2.9 au outbound.
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
Still possibleunchanged
What it implies
- The surface gas inbound was not representative of the body as a whole.For the key question: What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?
- Composition changed with depth or heating, not just with distance.For: Why did 3I/ATLAS's activity and chemistry change so much across perihelion?
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 3
SRC
SRC
Near-perihelion activity and composition of 3I/ATLAS from JUICE/MAJIS observations
SRCBockelee-Morvan et al. 2026
Cite it
Mysteries Department. (2026). CO2-to-water ratio fell from 7.6 to about 0.1 [Evidence EVD0DFQ3VTKN1HK]. https://mysteriesdept.com/r/EVD0DFQ3VTKN1HK
@misc{mysteriesdept_evd0dfq3vtkn1hk,
title = {CO2-to-water ratio fell from 7.6 to about 0.1},
author = {{Mysteries Department}},
year = {2026},
note = {Evidence, catalog key EVD0DFQ3VTKN1HK},
url = {https://mysteriesdept.com/r/EVD0DFQ3VTKN1HK}
}