# A crust made by cosmic rays on the journey

> Still possible: Billions of years of galactic cosmic rays reworked the outer metres of 3I/ATLAS, so the CO2-rich, red coma seen inbound came from a…

Source: https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ17SXMJ3A/a-crust-made-by-cosmic-rays-on-the-journey  
Publisher: Mysteries Department  
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[Questions](https://mysteriesdept.com/questions)[3I/ATLAS](https://mysteriesdept.com/mysteries/3i-atlas)[What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0HS0K7SD/what-is-3i-atlas-made-of-and-why-is-its-chemistry-so-unlike)Answer

Answer · 3I/ATLAS

# A crust made by cosmic rays on the journey

Billions of years of galactic cosmic rays reworked the outer metres of 3I/ATLAS, so the CO2-rich, red coma seen inbound came from a processed crust rather than the pristine interior.

**Still possible** Answers **1** question0

## Where it stands

**Still possible** Two pieces of evidence for, none against. It needs two reviews to be accepted.

## What it predicts

- The coma's composition shifts as the outer metres are lost
- Methane and other volatiles appear late, from below the processed layer

## What would rule it out

- The coma's composition stays the same after more than about 20 m of surface has been removed

## Evidence 2 for · none against

[CO2-to-water ratio fell from 7.6 to about 0.1](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3VTKN1HK/co2-to-water-ratio-fell-from-7-6-to-about-0-1)

Supported

FOR

[Cosmic-ray processing explains the CO2 and the red colour](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ3VE858GD/cosmic-ray-processing-explains-the-co2-and-the-red-colour)

Suggestive

FOR

## The questions it answers

[What is 3I/ATLAS made of, and why is its chemistry so unlike a Solar System comet's?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0HS0K7SD/what-is-3i-atlas-made-of-and-why-is-its-chemistry-so-unlike)

OpenNo answer ahead yet

## Cite it

```
Mysteries Department. (2026). A crust made by cosmic rays on the journey [Answer ANS0DFQ17SXMJ3A]. https://mysteriesdept.com/r/ANS0DFQ17SXMJ3A
```

Key

**ANS** 0DFQ17SXMJ3A

Kind

Answer · hypothesis

Proposed

[Session 1](https://mysteriesdept.com/mysteries/3i-atlas/sessions/SES0DFQC03S98K5/session-1-3i-atlas-opened-the-literature-to-november-2026) · 2 Nov 2026

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