SUPPORTING ONLINE MATERIAL (SOM)
Jupiter’s atmospheric composition from the Cassini thermal infrared
spectroscopy experiment
V. G. Kunde1*, F. M. Flasar2, D. E. Jennings2, B. Bézard3, D. F. Strobel4, B. J. Conrath5, et
al.
Text
S1 – Text: Jupiter’s North Auroral Infrared Hot Spot Energetics
The excess infrared emission from the North auroral hot spot in the measured hydrocarbon
lines may be determined from the radiance difference spectra shown in Figs S8a, 8b. From
integration of the difference spectrum over the hydrocarbon bands, we derive an excess
energy of 4 (±0.08) x 10-6 W cm-2 sr-1, where the error bar is the formal value from the
instrument random noise level (NESR). This assumes that the continua are the same inside
and outside the hot spot in the difference spectra; the excess energy thus originates only
from the stratospheric hydrocarbon lines. This assumption is not strictly true in the 600 cm-1
region where the continuum is about 10 – 15 % higher outside the spot relative to inside.
However, this deviation is small with respect to the total excess energy, and is not
considered further in this calculation. The air mass inside the hot spot is about 10% higher
than for the non-auroral selection. This accounts for a small fraction of the "excess energy".
Correcting for this effect, the excess energy is 3.6 (±0.08) x 10-6 W cm-2 sr-1.
Determination of the excess outgoing power from the excess energy requires information
on: 1) size of the emitting hot spot relative to the size of the CIRS FOV, and 2) the angular
variation of the emission.
1) Hot spot size. The CIRS FOV projected on Jupiter by an mid-infrared array pixel (.3mrad) is about 3600 km in longitude and 13000 km in latitude (area = 4.87 x 107 km2). The
spot is thus resolved both in latitude and longitude (our maps of the C2H2 and CH4
1
emissions indicate an extension of about 23000 km in latitude and 13000 km in longitude).
The flux difference between inside the hot spot (Fs) and outside the hot spot in the
surrounding region (F0) is
Fs − F0 = 2π
1
∫ [I (µ) − I (µ)]µdµ
0
s
0
(1)
where µ is the cosine of the emission angle of the radiance, and I(µ) is the measured
radiance.
The excess power for the projected FOV smaller than the spot is
∆P = ( Fs − F0 )A S
(2)
where AS is the area of the spot, and the overbars denote an average over the FOV.
2) Angular variation of the emission. As the angular variation of the emission is not
known, two extreme cases are used:
1) Optically Thick
∆P ≅ π ( I s − I 0 ) A s
This limit yields 2.8 x 10 W for the outgoing power.
(3)
13
2) Optically Thin
∆P = 2π [I s ( µˆ ) − I 0 ( µˆ )]µˆAs
(4)
This limit yields 1.6 x 1013 W for the outgoing power. From the two limits, the range in the
excess outgoing infrared power is 1.5-3 x 1013 W. This includes uncertainties in the
angular dependence of the spectral radiance, the lower (resp. upper) bound corresponding to
optically thin (resp. thick) emission.
The average excess flux over the northern spot (determined from ∆P / As) is 6-11 × 10-6 W
cm-2. It should be noted that this value for the outgoing power essentially is a snapshot for
2
January 8, 2001. The CIRS data, as well as other auroral studies, exhibit temporal
variations, both in and out of the hot spot.
References
S1. M. Wong, G. L. Bjoraker, M. D. Smith, F. M. Flasar, C. A. Nixon, et al, Planet.Space
Sci, 52, 385 (2004)
S2. A. Coustenis, B. Schmitt, R. K. Khana, F. Trotta, Planet. Space Sci. 47, 1305 (1999).
S3. E. Lellouch, B. Bézard, T. Fouchet, H. Feuchtgruber, T. Encrenaz et al., Astron.
Astrophy, 370, 610 (2001)
S4. D. G. Gautier, B. Bezard, A. Marten, J. P. Baluteau, N. Scott, et al ApJ., 257, 901
(1982).
S5. E. Lellouch, B. Bézard, J. I. Moses, G. R. Davis, P.Drossart et al., Icarus 159, 112
(2002).
Figures
3
Tropospheric Emission
140
H2
S(0)
H2
S(1)
120
Fig 1a
NH3
Brightness Temperature (K)
100
200
120
400
500
600
Strat
C2H6
Strat
C2H2
140
300
H2
S(1)
Trop
NH3
600
700
800
900
Fig 1b
1000
1100
Stratospheric Emission from CH4
160
140
120
1100
Fig 1c
1150
1200
1250
1300
-1
1350
1400
Wavenumber (cm )
Fig. S1. Representative thermal-emission spectra of Jupiter at low latitudes, with the fields
of view centered between 20° S and 20° N, Dec. 8, 2000. The spatial resolution is
approximately Jupiter’s disk radius for the far-infrared spectral region (top panel), and 6°
latitude for the middle-infrared region (bottom two panels). The spectral resolution is .52
cm-1 apodized. a) Far infrared spectral region showing tropospheric absorption lines of
NH3 and pressure-broadened molecular H2. The observed spectrum in the 300 – 600 cm-1
has been smoothed to wash out effects due to interference spikes. b) Mid-infrared spectral
region showing tropospheric absorption lines of NH3 and pressure-broadened molecular H2,
and stratospheric emission features of C2H2 and C2H6 c) Mid-infrared spectral region
showing stratospheric emission features of CH4. Weak spectral features from most minor
constituents listed in Table 1 are present in the above spectra, but are not visible at this
scale.
4
Radiance Difference: North Polar - Nonpolar
5e-8
4e-8
C 2H 2
3e-8
C 6H 6
2e-8
Broad Unidentified Feature
1e-8
Quadratic
Fit
0
-1e-8
670
680
690
700
710
720
730
-1
Wavenumber (cm )
Fig. S2. Radiance difference spectrum illustrating a broad (690 – 710 cm-1) unidentified
emission feature in Jupiter’s north polar atmosphere. The north polar spectrum and
nonpolar spectra used in the differencing are averages for 60º to 90º north latitude, and 50º
south to 50º north latitudes respectively. This spectral feature is also present in Jupiter’s
south polar region, albeit at a lower amplitude. The feature has also been seen in Voyager
IRIS spectra of Titan (S2), suggesting its origin may be a solid hydrocarbon condensate.
5
140.0
Brightness Temperature (K)
135.0
HD
R(0)
Rot
CH4
Rot
CH4
Rot
CH4
Rot
CH4
Rot
CH4
130.0
PH3
PH3
125.0
PH3
PH3
120.0
NH3
NH3
NH3
115.0
110.0
60
----- Observed Spectrum
----- Synthetic Spectrum without CH4, HD
----- Synthetic Spectrum with CH4, HD
70
80
90
Wavenumber (cm-1)
100
110
Fig. S3. The far infrared rotational lines of CH4 have been identified for the first time in
Jupiter’s atmosphere. The observed spectrum is an average of 1319 individual spectra
centered on Jupiter’s equatorial region. This average encompasses a substantial fraction of
Jupiter’s disk including both belts and zones, due to the large instrument footprint for this
focal plane. The spectral resolution is 0.26 cm-1 unapodized. The location of the HD R(0)
is also shown. Representative synthetic spectra are shown with and without the CH4 and
HD lines to aid in their identification in the observed spectrum. The synthetic model used a
ISO D/H ratio = 2.25 105 (S3), and a Galileo probe C/H ratio = 1.8 10-3 (S4). H2O lines
have not been detected in this average spectrum, a result which is consistent with the disk
averaged water abundance observed by ISO (S5).
6
- Average = 6294 spectra
- Avg Emission Angle = 56.5
C 2H 2
1.2e-7
Radiance
1.1e-7
HCN
C2 H 2
Observed
Spectrum
Synthetic Spectrum
w/35ppb HCN
1.0e-7
9.0e-8
Synthetic Spectrum
w/out HCN
710
711
712
Wavenumber, cm-1
713
714
7/31/2003
Fig. S4. Observed spectrum of Jupiter illustrating the first identification of the Q-branch of
HCN at 712 cm-1. The observed spectrum is an average of 6294 spectra located in a 10°
latitude bin, centered at 45° south. The spectral resolution is 0.26 cm-1 unapodized. The
synthetic comparison curves are shown without HCN, and with 35ppb HCN above the 1
mbar level.
7
1.25e-7
- Average = 6294 spectra
- Average Emission Angle = 56.5
CO2
1.20e-7
Radiance
Observed
Spectrum
Synthetic Spectrum
w / 5ppb CO2
C2 H2
1.15e-7
Synthetic
Spectrum
without CO2
1.10e-7
664
666
668
670
Wavenumber, cm-1
672
674
7/31/2003
Fig. S5. Observed spectrum of Jupiter illustrating the CO2 emission feature at 667 cm-1.
The observed spectrum is an average of 6294 spectra located in a 10° latitude bin, centered
at 45° south. The spectral resolution is 0.26 cm-1 unapodized. The synthetic comparison
curves are shown without CO2, and with 5ppb CO2 above the 1 mbar level.
.
8
Fig. S6 –Unapodized (0.26 cm-1) radiances in a spectral region containing emission from
CO2 (668 cm-1) and C6H6 (674 cm–1), observed at different locations on Jupiter. In all
cases, the underlying “continuum” has been removed, by smoothing each spectrum to 20
cm-1 resolution and subtracting that from the original. Waterfall plot. Spectra in the
southern hemisphere, averaged in 10° latitude bins (with the exception of the southernmost,
which covers 70° S to 90° S), plotted at the average bin latitudes. The bins include spectra
at very high emission angle, for which the field of view was partially off Jupiter’s disk, so
the averaged spectra were renormalized by dividing by their average filling factors. Note
the gradual increase in CO2 emission from mid to high southern latitudes. The vertical bars
indicate the variation of the average air mass with latitude. The abrupt enhancement in
C6H6 is attributable to emission from the southern auroral hot spot. Top inset. Average
radiances at 76° N and S. The enhanced C6H6 emission is mainly from the northern and
southern auroral hot spots. Although CO2 emission is enhanced in the south, it is only
weakly visible in the north. Bottom inset. Radiances averaged over 60° S – 90° S, within
the auroral hot spot (0° – 100° W) and outside it (150° W – 270° W). The C6H6 emission
is enhanced only within the hot spot, whereas the CO2 emission is nearly identical within
and outside the spot.
9
8e-8
North
Radiance, W cm
-2
ster
-1
-1
/ cm
C2H4
4e-8
0
930
940
950
Wavenumber (cm-1)
960
970
Fig S7. High spectral resolution (0.52 cm-1 apodized) radiance measurements in the
northern auroral infrared hot spot, showing enhanced hydrocarbon emissions due to C2H4.
The observed spectrum is an average of 256 spectra for the time period Jan 1 - Feb 12 2001,
all at high emission angles (60 - 90º). These spectral emissions originate in the warm
stratosphere, at altitudes from ~ 5 mbar to ~ 1 µbar.
10
1.0e-7
Radiance (Inside Spot - Outside Spot)
Fig. 7a
8.0e-8
6.0e-8
C2H6
C2H2
C6H6
4.0e-8
CH3
C3H4
2.0e-8
600
650
700
750
800
850
Wavenumber (cm-1)
4.0e-8
Radiance (Inside Spot - Outside Spot)
Fig. 6B
CH4
3.0e-8
2.0e-8
1.0e-8
1225
1250
1275
1300
Wavenumber
1325
1350
1375
(cm-1)
Fig. S8. Radiance differences (data within the hot spot minus that outside the hot spot) are
shown for the northern auroral hot spot. These spectral enhancements arise due to
differences in temperature and/or composition in the hot spot, relative to the hot spot
surroundings, from charged particle impacts. Spectral integration of these radiance
differences gives the excess infrared power (excess relative to the surroundings) radiated
from the north hot spot. The hot spot boundaries are defined by 65-75 N latitude, and 170180 longitude, with the emission peaking at 73°N latitude and 180°W longitude.
a). The average spectrum is for 10 individual spectra, the average emission angle is 74.9º.
The enhanced emissions of the stratospheric hydrocarbons, CH3, C3H4 (methyacetleyene),
C6H6 C2H2, C2H6, , and C2H4 within the north auroral infrared hot spots are shown.
b). The average spectrum is for 10 individual spectra, the average emission angle is 73.9º.
The enhanced emissions of CH4 within the north auroral infrared hot spot are shown.
11
Table S1. Jovian Atmospheric Constituents Observed by CIRS
Spectral Region (cm-1)
Gas
*Comments
MAIN CONSTITUENTS
Hydrogen
H2
**Methane
CH4
TROPOSPHERIC CONSTITUENTS
Ammonia
NH3
Phosphine
STRATOSPHERIC CONSTITUENTS
HYDROCARBONS
Acetylene
Ethane
Methyl Radical
Ethylene
Methylacetylene
Benzene
Diacetylene
OXYGEN COMPOUNDS
Carbon dioxide
CARBON-NITROGEN COMPOUNDS
Pressure Induced:
Dimer:
Quadrupole:
Rotational:
ν4:
50 - 600
354, 587
587
70 - 120
1200 - 1400
PH3
Rotational:
ν2:
Rotational:
ν2:
ν4:
20 - 250
800 - 1100
20 - 100
980 - 1000
1120 - 1190
C2H2
C2H6
CH3
C2H4
C3H4
C6H6
C4H2
ν5:
ν9:
ν2:
ν7:
ν9:
ν4:
ν8:
CO2
ν2:
700 - 760
800 - 840
601 - 606
910 - 990
630 - 637
674
628
667
12
First ID of rotational lines in Jupiter’s atmosphere
N. & S. infrared hot spots enhanced
N. & S. infrared hot spots enhanced
N. & S. infrared hot spots enhanced
First detection, N. & S. infrared hot spots enhanced
N. & S. infrared hot spots enhanced
N. & S. infrared hot spots enhanced
N. & S. infrared hot spots enhanced
First detection, N. & S. infrared hot spots enhanced
Abundance peaks at high S. Latitudes
Hydrogen Cyanide
HCN
ν2:
712
First ID of Q-branch
ISOTOPES
Deuterated hydrogen
Monodeuterated methane
Isotopic methane
Isotopic ethane
Isotopic ammonia
Tropospheric Clouds
Water Ice
Ammonia Ice
Stratospheric Haze
Solid haze feature?
HD
CH3D
13
CH4
13
C2H6
15
NH3
Rotational: R(0) @89.2, R(2) @265.3
H O Ice
2
Nu_T translational lattice band: 229
ν2:
1060
NH3 Ice
ν6:
ν4:
ν9:
ν2:
1156
1250 - 1350
821.6
863, 883, 903, 943
Origin Unknown
693 - 707
Observed at low latitudes
First detection
(S1)
First detection: Observed at N. & S. polar latitudes
*In the Comments column, the designation “first detection” means this molecule is a newly identified molecule (i.e. CH3 and C4H2);
the designation “first ID” means this is the first identification of a molecular line of an already known species (i.e. rotational lines of
CH4, HCN; Figs. S3).
* *Italics denotes species newly detected by CIRS, and the first identification of molecular lines of an already known species.
•
13
Table S2. Geometry Parameters for North Hot Spot Energetics
Spectral
Number Average Latitude
for FOV
Range/Insideof
Center Point
Outside Hot Spot Spectra
in
Average
Average Longitude
for FOV
Center Point
Average
Emission Angle
for FOV
Center Point
(Deg)
Range
in
Latitude
Range
In
Longitude
Range
In
Emission
Angle
(Deg)
600-850 cm-1 Inside Hot Spot
10
70.1
174.8
74.9
69.3 – 70.8
171.0 – 178.8
73.9 – 75.6
600-850 cm-1 Outside Hot Spot
50
68.9
91.9
73.4
65.0 – 70.8
77.0 – 108.7
68.9 – 75.4
1200-1400 cm-1 Inside Hot Spot
10
70.8
173.7
73.9
70.1 – 74.0
170.9 – 176.5
68.0 – 77.7
1200-1400 cm-1 Outside Hot Spot
27
71.1
79.1
74.2
68.8 – 73.9
71.4 – 87.4
71.8 – 77.3
14