Table 1 Compilation of Cassini’s INMS data on Enceladus’ plume composition over the last decade

From: Biological methane production under putative Enceladus-like conditions

Speciesa

Volume mixing ratio

 

Waite et al. 20063

Waite et al. 20094

Waite et al. 201125

Perry et al. 201526

Bouquet et al. 20155

Waite et al. 2017b,2

H2O

90.7–91.5

90.0 ± 1.0

92.0 ± 3.0

>90

87

96–99

CO2

3.14–3.26

5.3 ± 0.1

0.8 ± 0.3

0.6 ± 0.2

0.52

0.3–0.8

CO

(3.29–4.27)

(4.4)

<1.5

 

≤0.64

 

H2

 

(39)

<3.4 ± 1.0

1–5

11

0.4–1.4

CH2O

 

0.31 ± 0.01

<0.032

   

CH3OH

 

0.015 ± 0.006

0.003 ± 0.002

   

C2H4

 

<1.2

    

H2S

 

0.0021 ± 0.0010

0.003 ± 0.001

 

0.0021 ± 0.0010

 

NH3

 

0.82 ± 0.02

0.8 ± 0.03

0.9 ± 0.04

0.61

0.4–1.3

N2

(3.29–4.27)

<1.1

  

≤0.61

 

HCN

 

<0.74

0.7 ± 0.3

 

≤0.12

 

CH4

1.63–1.68

0.91 ± 0.05

0.21 ± 0.09

0.2 ± 0.1

0.19

0.1–0.3

  1. a Values used in this study are marked in bold
  2. b These recent observations based on the data of flyby E21 lead to the assumption that H2O is even more prominent, whereas the concentrations for the other major species (NH3, CO2, and CH4) varied only slightly. The other components were categorised as minor species with moderate ambiguity (e.g., CO, N2, C2H4, or CH2O) or as potential species with high ambiguity (e.g., H2S or CH3OH)6
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