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H ratios in the atmospheres of Jupiter and Saturn
ICARUS
52, 54-61 (1982)
On the C/H and D/H Ratios in the Atmospheres T. ENCRENAZ Observatoire
AND
de Meudon,
Received December
of Jupiter
and Saturn
M. COMBES
92190 Meudon,
France
16, 1981; revised May 19, 1982
Using a method defined in a previous paper [M. Combes and T. Encrenaz, Icarus 39 1-27 (1979)], we reestimated the C/H ratio in the atmospheres of Jupiter and Saturn by the measurements of the weak visible CHI bands, the CH, 3q band, and the (3-O) and (4-O) quadrupole bands of Hr. In the case of Jupiter we conclude that the C/H ratio is enriched by a factor ranging from 1.7 to 3.6 relative to the solar value. In the case of Saturn, our derived C/H value ranges from 1.2to 3.2 times the solar value. The Jovian D/H ratio derived from this study is 1.2 x 10m5< D/H < 3.1 x 10m5.The value derived for the D/H ratio on Saturn is not precise enough to be conclusive.
INTRODUCTION
In spite of the remarkable results obtained on the composition of Jupiter and Saturn atmospheres from the Voyager data, there is still some uncertainty in the determination of some elemental and isotopic ratios such as C/H and D/H. In the case of Jupiter, before Voyager, results on C/H obtained from various methods ranged from a slight enrichment (Combes and Encrenaz, 1979; Encrenaz et al., 1980) to an enrichment by a factor of 3 to 5 (Cochran, 1977; Sato and Hansen, 1979; Buriez and de Bergh, 1980). The most recent determination (Gautier et al., 1981), using the Voyager IRIS data in the red wing of the CH4 uq band, concludes to an enrichment by a factor of 2.07 5 0.24 relative to the solar value. In a study by Gautier et al. (1981), as well as in the present work, the solar C/H value is taken as equal to 4.7 x 10P4, following Lambert’s (1978) determination. In the case of Saturn, the C/H value derived from scattering models ranges from 2 to 6 times the solar value (Buriez and de Bergh, 1981). Concerning the D/H ratio on Jupiter, recent determinations using the CH,D/H2 ratio derived from groundbased and Voyager IRIS data have led to a D/H ratio in the range 2-3 X 10M5(Encrenaz et al., 1980; Kunde et al., 1981; Drossart et al., 1982). In the case of 54 0019-1035/82/100054-08$02.00/O Copyright 0 1982 by Academic Press. Inc. All rights of reproduction in any form reserved.
Saturn, the first D/H determination using HD and Hz lines was made by Macy and Smith (1978), who derived a value of 5.5 * 2.9 x 10e5. More recently, a different estimate of D/H on Saturn was made by the use of CH,D lines: from near-ir spectra of Saturn, de Bergh ef al. (1981) derived a much lower D/H value (D/H < 1.25 x 10es). One of the various causes of uncertainty is the laboratory measurement of the absolute intensity of the hydrogen quadupole lines. In the case of the (4-O) band, in particular, two laboratory measurements (Bergstrahl et al., 1978; Trauger et al., 1978) found for the S1(4-0) line an absolute intensity significantly smaller than the theoretical determination of Dalgarno et al. (1969); this value was used in the study of Combes et al. (1978) and Combes and Encrenaz (1979). However, a more recent laboratory measurement by Brault and Smith (1980), using improved laboratory data, concludes to a S,(4-0) intensity in good agreement with the theory. This new result has important consequences for the determination of both C/H and D/H on Jupiter and Saturn. In particular, it can be foreseen that the method Combes and Encrenaz (1979) used with the new H,(4-0) laboratory measurement of Brault and Smith (1980) will lead to a Jovian C/H ratio in good agreement with the recent C/H result ob-
C/H AND D/H ON JUPITER AND SATURN
tained by Voyager on Jupiter (Gautier et al., 1981). In this paper, we first reapply the method defined in Paper I (Combes and Encrenaz, 1979) to the case of Jupiter, with three important improvements: (1) the new CH4 laboratory and planetary data of Lutz et al. (1981) have been taken into account; (2) the new measurement of the Sr(4-0)H2 quadrupole line obtained by Brault and Smith has been used; (3) Hz quadrupole line collision narrowing has been analyzed on the basis of Galatry’s profiles, as calculated by James (1969). Then we study how the method defined in Paper I can be applied to Saturn, and we consider the case of C/H and D/H. JUPITER
The principles of the method described in detail in Paper I can be summarized as follows. In most of the cases, the apparent abundances derived from the reflecting layer model (RLM) for two different species cannot be directly ratioed in order to obtain a reliable abundance ratio of the two species, because the scattering processes are likely to be different for the two lines or bands used for determining the apparent abundances. For this reason, we selected a set of four conditions which determines the choice of pairs of lines (or bands) of two different species, so that the scattering processes are necessarily the same for both lines. These four conditions are (I) the two lines or bands have to be chosen in the same spectral range; (2) the two lines or bands must have the same depth on the planetary spectrum; (3) the ratio to be measured must be constant with height; (4) the two absorption coefficients must have the same dependence on temperature and pressure. As discussed in detail in Paper I, the number of ideal cases for which spectroscopic data exist is very limited (12C/13C,D/ C); then, in order to extend our method to other abundance ratios, we had to consider some possible departures from some of these conditions. It has been shown (see Paper I> that two conditions are specially
55
important: condition 2 (same depth of the two lines or bands) and condition 3 (homogeneously mixed constituents). As a consequence, the case of C/H was considered in Paper I, in spite of the strong departure from condition 4 due to the pressure narrowing of the H2 lines. In what follows, we reconsider the determination of C/H on Jupiter with our method, taking into account that some uncertainty may come from the departure from condition 4. Figure 1 shows the apparent abundance of CH4 on Jupiter as a function of the depth of the CH4 bands in the laboratory spectrum. This figure is similar to Fig. 3 of Paper I, except that the recent laboratory data of Lutz et al. (1981) have been taken into account. In particular, following Lutz et al. (1981), the 6825-A band has been withdrawn, because, according to Lutz et al., some other absorber is possibly responsible for part of the absorption. It can be seen that the shape of the curve in Fig. I is in agreement with the theoretical curve that we derived from McElroy’s calculations (1969) for a homogeneous scattering model with isotropic scattering (Fig. 2). In particular, the “plateau” shown for the weak
I
0.97
I -6
I
-”
-5 -4 Log (S,/17,,)(cm-Am)-'
.
-3
FIG. 1. Apparent abundance of CH4 on Jupiter, defined as ACH4 = (mylS,,)log [I/( I - p)] (p = depth of the Jovian line or band) as a function of S&y, measured in the laboratory. (SO = Absolute intensity of the CH4 line; y,, = half-width of the CH, line.) This apparent abundance is in fact the abundance derived with the RLM assumption. The data include the 3v, points at 1 .I km for log (S&r) > -5, taken from Lecacheux et al. (1976), the visible CH, bands taken from Lutz et al. (1976, 1981), and the measurement of Mickelson et al. (1977). This figure is similar to Fig. 3 of Paper I, except that the laboratory data have been updated.
56
ENCRENAZ
RLM
Curve
of
growth
AND COMBES
results is the use of the new laboratory determination of S,(S,(4-O)), which increases our previous result of C/H (see Paper I) by approximately 2. From Fig. 3 we derive 300 < p < 600
for the (4-0)Si line
and 250 < p
for the (3-0)Si line.
The first set of unequalities I
I
0.01
0.1
I 1
I 10
8.3 x 1O-4 < C/H < 1.7 x 1O-3
w
FIG. 2. Apparent abundance as a function of the absorption coefficient at the center of a Lorentz line, estimated from McElroy (1969) calculations. The abscissa unit is w = u&u + k), where o and k are the scattering coefficient and the absorption coefficient in the continuum, respectively. The single-scattering albedo in the continuum is w, = u/(u + k) = 0.99. The related curve of growth departs from linearity for w > 0.01, while for a pure absorbing atmosphere (RLM, wc = 0) the transition from linear to square-root regime occurs only for u’ > 1.
bands [S/n-y < 5 x 10m6(cm.Am)-I] seems to correspond to the horizontal part of the theoretical curve ((Y&U + k) < 0.01) for which the absorption coefficient is negligible compared to the scattering coefficient. Table I summarizes the data included in our calculations and the quantities used for the determination of the C/H ratio. A basic limitation comes from the variations of the H2 quadrupole line intensities, especially for the &(3-O) line. We took mean values of these quantities with appropriate error bars, following the analysis of Margolis and Hunt (1973). In the case of CH4, the intensities of the Jovian bands seem less variable with time (Lutz et al., 1976, 1981). The CH, data at 1.1 p,rn, which are used for the C/H determination, refer, as in the case of the Hz lines, to the center of the disk (q = 2.1; see Paper I). Figure 3 shows our new determination of C/H on Jupiter using the quantities calculated in Table I. The technique used for building the figure and deriving the final range of p values is fully described in Paper I. The main difference with our previous
implies
C
i!Hv1 = 1.2:;:;
x 10-3 . )
Using Lambert’s (1978) determination the solar C/H ratio our result implies
of
Using a previous D/C determination given in Paper I (1.0 X lo-’ < D/C < 2.7 x 10m2)and combining quadratically the error bars we derive for D/H 1.2 x lop5 < D/H < 3.1 x 10p5.
-.-.
O.’ -
4-0
006
--g---
-5I Log I @/IT
y. ) , Log ( pZ&’
-4 ky
-3
I
FIG. 3. Determination of the C/H ratio on Jupiter by a comparison of our ACH4 curve to the (4-O) and (3-O) quadrupole lines of H,. The dashed line represents a least-squares fit of A(CH,) points. ACH4 and A,, are in km-Am, SOCWnyo and .S,Wky are in (cm-Am)-‘. The H2 observational data are indicated by the two sets of horizontal lines. In each case, the curve pMEAS = plNITIALdefines the points for which the p ratio read on the ordinates (AH21ACH4)is equal to the p ratio read on the abscissae [( SOCH4 Inyc& .S,,,,/ k-yHZ)]. The intersections of these two curves with the error bars of the measurements give the possible range of p values on Jupiter. See Paper I for more details on the method.
_
3.3 x 10-n 20 *4 Average 1963-1972 2.0 (Center of disk)
22.5 + 5 66 +5
3.5 x 10-7 74 r 30
Average 1963-1972 2.0 (Center of disk)
145 t 85 51 ? 30
[(cm-Am)-‘] f
2.5 (Central meridian) 30 2 8 75 +- 20
x 10-s
2.5 (Central meridian) 140 2 80 42 2 24
3.3
x 10-r
26 ~fr6 Average 1970-1975
x IO-’
2.1
1.59 x 10-g
-1.0
130
0.6367
S,(4-0)
72 t 30 Average 1970-1975
3.6
1.6 x IO-*
1.34 x 10-s
-1.0
130
0.8150
S,(3-0)
Saturn
a.6 Mean temperature and pressure of the planetary atmosphere in the region of line formation. eAbsolute intensity of the Hz line, at the temperature of line formation. d Half width of the Hz line. e Absorption coefficient of the H2 line at the central frequency (see Combes and Encrenaz, 1979). f Equivalent width of the H2 line on the planetary spectrum. 8 Air mass factor. h Apparent abundance of HZ in the planetary atmosphere, derived in the reflecting layer model approximation.
S,,qA (m cm-l) A (km-Am)h
Time of observation ng
W (m cm-‘)’
x 10-r
S$dky
2.2
1.7 x 10-z
IO-9
y (cmm’)d
1.68 x
-1.0
1.40 x 10-g
-1.0
P (atm)b
0.6367 150
S,(4-0)
SaH2(cm-i/cm.Am)’
0.8150 1.50
TW’
w
S,(3-0)
Jupiter
TABLE I
This paper This paper
Trafton (1977)
Margolis and Hunt (1973)
Combes and Encrenaz (1979) This paper Combes and Encrenaz (1979) This paper After Trauger et al. (1978) After Brault and Smith (1980) This paper After James (1969) This paper After Margolis and Hunt (1973) After Trafton (1977)
References
Y
ENCRENAZ AND COMBES
58
A,,_
SATURN
Figure 4 shows the apparent CH4 abundance for Saturn as a function of the depths of the CH4 lines or bands. The visible data were taken from Lutz et al. (1976, 1981). In the case of the 3u3 CH4 band at 1. I urn, we limited our study to the CH4 lines having a well-known temperature dependence, i.e., the J multiplets of the 3~ band. Following Lecacheux et al. (1976) we assumed a temperature of 130°K for the region of line formation on Saturn; according to Hanel et al. (1981) the pressure at this level is close to 1 atm. As shown in Fig. 4, the general shape of the ACHY curve looks similar to the Jupiter curve. It can be noticed that the ACH4 curve for Jupiter and Saturn appears basicaliy different from the ACH4 curve for Uranus and Neptune (Encrenaz and Combes, 1982), implying different scattering properties of the atmospheres. In Paper I we discussed in detail which abundance ratios could be derived by our method. It was shown that, in the case of Jupiter, the uncertainty due to a departure from the four ideal conditions was still acceptable for C/H so that a C/H ratio could be derived. In the case of Saturn, the ex-
?Ac,Jkm-Am) 1.0.
05-
f
* .. . O.?_T
I -6
I -5
I -4
-3
Log ( S~H4/lro) (cm-Ad’
FIG. 4. Apparent abundance of CH4 on Saturn as a function of S/.rry. The data include the 1. I-pm points [R(4), R(l), R(O), R(3), at log (S/my) > -41 taken from Lecacheux et al. (1976) and the visible bands at CH, taken from Lutz et al. (1976, 1981). The n factor is equal to 2.5.
, A,)
x IO3 1
0.4
0 H
2
,‘r
9
0.2 t
1
4_o
-6
+__k_3_o -4
-5
Log(S,CH4/rT, ) , Log(p+/
FIG. 5. Determination of parison of our A,,, curve to pole lines of H,. The dashed squares fit of the ACH4points A,, are in km-Am, SoWiny, Am))‘. The method is the Fig. 3.
kr)
C/H on Saturn by a comthe (4-O) and (3-O) quadrucurve represents a leastshown in Fig. 4. ACH4and and SoHz/ky are in (cmsame as that described in
petted line formation level is approximately at the same pressure level as for Jupiter (-1 atm), so that the method can also be used for determining the C/H ratio of Saturn; in contrast, for Uranus and Neptune, where the formation level occurs at a much higher pressure, the departure from condition 4 due to collision narrowing and pressure shift of the Hz lines cannot be neglected, so that our method cannot be used for a determination of C/H on these planets (Encrenaz and Combes, 1982). The numbers used in our calculations are listed in Table I. As for Jupiter, a major source of uncertainty comes from the variability of both the Hz intensities and some of the CH4 band intensities on the Saturn spectra (Trafton, 1977). The error bars on %’ take into account these uncertainties. For the H2 data, as for the CH, data, the r) factor is 2.5, so that both sets of data refer to the same portion of Saturn’s disk. As for Jupiter, most of the information comes from the Hz S,(4-0) line. Figure 5 shows our determination of C/H on Saturn, following the technique described in Paper I. The results shown in Fig. 5 are 330 < p < 800 250 < p
from the (4-O) band, from the (3-O) band.
C/H AND D/H ON JUPITER AND SATURN Our conclusion
is thus
330 < p < 800 or 6.2 x 1O-4 < (C/H)I, < 1.5 x 10-3, which implies, assuming Lambert’s value for the solar C/H, 1.2(C/H)o < (C/H)r, < 3.2 (C/H). ((C/H)r, = l.O$j
(1978)
59
D/C value derived on Jupiter (1 to 2.7 x lo-*; see Paper I) and on Uranus [<6 x 10m3;Encrenaz and Combes, (1982)J by the same method. Using our C/H determination on Saturn, and adding the error bars quadratically, we obtain a very high mean value for the H/D abundance ratio on Saturn: D/H = S+g x 10-j
x 10-3).
In conclusion, the C/H ratio seems to be approximately equal on Jupiter and Saturn. Both planets show a carbon enrichment, by a factor about 2 to 3, relative to the Sun. In order to estimate the D/H ratio on Saturn, we used our method with the HD observation of Macy and Smith (1978). These authors measured the HD(S-O)R(O) line and derived a D/H value by comparing their HD abundance to the H2 abundance measured from the (4-O)S, line. As for Jupiter, we first estimate D/C by using the HD observation and the A(CH4) curve. The following numbers are used: S~(HD)S_~ = 2.8 x 10m7 cm-‘/cm.Am at 130°K (after McKellar et al., 1976). Assuming a pressure of 1 atm, which is consistent with the atmospheric profiles of Hanel et al. (1981), the HD line halfwidth is y = 7 x 10m2cm-‘. The apparent HD abundance is A(HD) = 0.014 + 0.006 km.Am (Macy and Smith, 1978). The abscissa of the HD point in the (S/ ITS) scale is thus 1.2 X 10e6 (cm.Am))‘. As shown in Fig. 4, the abscissa corresponds to the horizontal plateau of the A(CH4) curve. In the region, we estimate A(CH4) = 450 + 100 m-Am. Thus we can derive the HD/CH4 ratio by simply taking the ratio of the apparent HD and CH4 abundances, 0.036 < HD/CH < 0.14 or D/C = 0.08 -+ 0.05. This value is significantly larger than the
or 2 x 10-j < D/H < 1.5 x 10-4. This value is larger than the estimate obtained by de Bergh et al. (1981) from the study of near-ir CH3D bands (D/H < 1.25 x 10m5).This value is also larger than the previous D/H estimate by Macy and Smith (1978), but this only comes from the reevaluation of the strength of the H2 Si(4-0) line; in the present case, the RLM estimate and our method give almost the same result, because the A(CH4) variation is small between the two abscissa values of Slay corresponding to the HD R0(5-0) and the H2 S1 (4-O) lines. CONCLUSION
Table II summarizes the most recent C/H and D/H results obtained on Jupiter and Saturn from visible and ir data using various methods. The conclusions of the present study are the followings: (1) the C/H ratio seems to be approximately equal in the atmospheres of Jupiter and Saturn. In both cases, the C/H ratio is enriched with respect to the solar value by a factor of about 2 to 3. This conclusion is different from the conclusion of Paper I. In the case of Jupiter, this result is in good agreement with the recent determination based upon the Voyager IRIS data (Gautier et al., 1981), implying an enrichment by a factor of 2.07 + 0.24. On the other hand, the reevaluation of our C/H value, due to the change in the measurement of the absolute strength of the H2 S,(40) line, gives a better agreement with the C/
ENCRENAZANDCOMBES TABLE 11 RECENT C/H
AND
D/H DETERMINATIONS ON JUPITER AND
SATURN
Saturn
Jupiter
Ground-based ir spectra (CH, yq band-g.5 km) IRIS (CHI Y.,band-8 pm) Scattering models (CH, 3v3-1. 1 pm) This work (visible + 1.1 p.m)
Ground-based ir spectra (CH2D Yeband-g.6 km) IRIS (CH,D Yeband-g.6 pm) + vZ band-4.5 pm) IRIS (CH3D Yeband-4.5 km) Scattering models (CH,D l-2 km) This work
C/H 110-3 (Encrenaz et al., 1980) 0.97 * 0.11 x 10-3 (Gautier et al., 1981) 1.3 -t 0.6 x IO-’ (Buriez and de Bergh, 1980) 1.2’8: x 10-3
2.0 2 1.0 x 10-3 (Buriez and de Bergh. 1981) 1.0’8: x 1om3
D/H 14 x 10-s (Encrenaz et al., 1980) 3.0’1:, x 10-S (Kunde er al., 1981) 1.8$$ x 10ms (Drossart et al., 1982) 2.0:;e x IO-’
H determination derived from the 3u3 CH4 band using scattering models [(C/H)11 = 1.5-4 x (C/H)o] (Buriez and de Bergh, 1980). In the case of Saturn, our result is in marginal agreement with Buriez and de Bergh’s (1981) estimate [(C/H),, = 2-6 x (C/H)O], but still compatible if we consider the error bars. (2) Concerning the Jovian D/H ratio, our value (1.2-3.1 x 10m5) is consistent with various other studies using the CH3D bands in the infrared spectrum of Jupiter. From ground-based observations at 8.6 pm, Encrenaz et al. (1980) derived a D/H upper limit of 4 x 10m5. Using the Voyager IRIS data at 5 and 8.6 p,rn, Kunde et al. (1981) found a D/H ratio ranging from 2 x 10-j to 4.5 X 1O-5. A similar estimate is given by Drossart et al. (1982) and Bjoraker et al. (1981). The D/H ratio derived on Jupiter is in reasonable agreement with the values measured in the local interstellar medium (Laurent, 1978) and with the value expected for the Primordial Nebula (Geiss
-
Cl.25 x 10-5 (de Bergh et a/., 1981) <1.5 x IO-4
and Reeves, 1972; Geiss and Bochsler, 1979). Concerning Saturn, the D/H value found in the present study appears to be questionable. More measurements of visible HD lines are certainly needed to confirm this result. REFERENCES BERGSTRAHL,J. T., J. S. MARGOLIS AND J. W. BRAULT (1978). Intensity and pressure shift of the H,(4-O)S, quadrupole line. Asrrophys. J. 224, L39-L41. BJORAKER,G., U. FINK, H. P. LARSON, AND V. KUNDE (1981). Abundance for Jovian belt regions from 5~ measurements. BAAS 13, 735-736. BRAGG, S. (1981). Ph.D. thesis, Washington University, St. Louis, MO. BRAULT,J. W., AND W. H. SMITH (1980). Determination of the H, 4-O S(1) quadrupole line strength and pressure shift. Astrophys. J. 235, L177-L178. BURIEZ, J. C., AND C. DE BERGH(1980). Methane line profiles near 1.1~ as a probe of the Jupiter cloud structure and C/H ratio. Astron. Astrophys. 83, 149-162. BURIEZ, J. C., AND C. DE BERGH (1981). A study of the atmosphere of Saturn based on methane line profile near 1.1 t.~.Astron. Astrophys. 94, 382-390.
C/H AND D/H ON JUPITER AND SATURN, COCHRAN,W. D. (1977). Jupiter: An inhomogeneous atmospheric model analysis of spatial variations of the H,(4-0) S, line. Icarus 31, 325-347. COMBES,M., T. ENCRENAZ,AND T. OWEN (1978). On the abundance of deuterium in Jupiter’s atmosphere. Astrophys. .I. 221, 378-382. COMBES,M., AND T. ENCRENAZ(1979). A method for the determination of abundance ratios in the outer planets. Application to Jupiter. Icarus 39, l-27. DALCARNO,A., A. C. ALLISON, AND J. C. BROWNE (1969). Rotation-vibration quadrupole matrix elements and quadrupole absorption coefficients of the ground electronic states of H,, HD and DZ. J. Atmos. Sci. 26, 946-95 1. DE BERCH, C., B. L. LUTZ, G. W. LOCKWOOD, T. OWEN, J. BRALJLT,AND J. C. BURIEZ (1981). Detection of CH,D and measurements of the CH,D/CH, ratio on Titan and Uranus. BAAS 13, 703. DROSSART,P., T. ENCRENAZ,V. KUNDE, R. HANEL, AND M. COMBES (1982). An estimate of the PH?, CH,D and GeH, abundances on Jupiter from the Voyager IRIS data at 4.5 pm. Icarus, in press. ENCRENAZ,T., AND T. OWEN (1973). New observations of the hydrogen quadrupole lines on Saturn and Uranus. Asfron. Astrophys. 28, 119. ENCRENAZ,T., M. COMBES,ANDY. ZEAU (1980). The spectrum of Jupiter between 8 and 9 microns : Estimates of the Jovian C/H and D/H ratios. Astron. Astrophys.
84, 148-153.
ENCRENAZ,T., AND M. COMBES(1982). On the D/C ratio in the atmosphere of Uranus. Icarus 49, 2734. FINK, U., AND M. J. S. BELTON (1979). Collisionnarrowedcurves of growth for HZ applied to new photoelectric observation of Jupiter. J. Atmos. Sci. 36, 952-962. GAUTIER,D., A. LACOMBEAND I. REVAH (1977). Saturn: Its thermal profile from infrared measurements. Astron. Astrophys.
61, 149-153.
GAUTIER, D., B. BEZARD, A. MARTEN, AND J. P. BALLJTEAU(1981). The C/H ratio in Jupiter from the Voyager experiment. BAAS 13,738. GEISS, J., AND H. REEVES (1972). Cosmic and solar system abundances of deuterium and helium 3. Astron. Astrophys. 18,126-132. GEISS, J., AND P. BOCHSLER(1979). On the abundances of rare ions in the solar wind. In Proceedings,
4th
Solar
Wind Conference,
Burghausen.
Springer-Verlag, Berlin/Heidelberg/New York. HANEL, R., B. CONRATH,M. FLASAR, V. KUNDE, W. MAGUIRE,J. PEARL, J. PIRRAGLIA,R. SAMUELSON, L. HERATH, M. ALLISON, D. CRUIKSHANK, D. GAUTIER, P. GIERASCH, L. HORN, R. KOPPANY, AND C. PONNAMPERUMA(1981). Infrared observations of the Satumian system from Voyager I. Science 212,192-200. JAMES, T. C. (1969). Calculations of collision narrow-
61
ing of the quadrupole lines in molecular hydrogen. J. Opt. Sot. Amer. 59, 1602-1606. KUNDE, V., R. HANEL, W. MAGUIRE, D. GAUTIER,J. P. BALUTEAU, A, MARTEN, A. CHEDIN, N. HusSON, AND N. SCOTT (1981). The lower atmosphere composition of Jupiter’s north equatorial belt from Voyager 1 IRIS. BAAS 13, 735. LAMBERT,D. (1978). The abundances of the elements in the solar photosphere. VIII. Revised abundances of carbon, nitrogen, and oxygen. Mon. Not. Roy. Astron. Sot. 82, 249-272.
LAURENT, C. (1978). L’abondance
du Deuterium interstellaire a partir dur satellite Copernicus et ses implications astruphysiques. These de Doctorat
d’Etat, Universite de Paris VII. LECACHEUX,J., C. DE BERGH, M. COMBES,AND J. P. MAILLARD(1976). The C/H and 1ZCH41r3CH4 ratios. in the atmospheres of Jupiter and Saturn from 0.1 cm-’ resolution near infrared spectra. Astron. Astrophys. 53, 29-33.
LUTZ, B. L., T. OWEN, AND R. D. CESS (1976). Laboratory band strengths of methane and their application to the atmospheres of Jupiter, Saturn, Uranus, Neptune and Titan. Asrrophys. J. 203, 541-551.
LUTZ, B. L., T. OWEN, AND R. D. CESS (1981). Laboratory band strengths of methane and their application to the atmospheres of Jupiter, Saturn, Uranus, Neptune, and Titan. II. The red region 6000-7600 A. In press. MCELROY,M. B. (1969). Atmospheric composition of the Jovian planets. J. Atmos. Sci. 26, 798-812. MCKELLAR,A. R. W., W. GOETZ, AND D. A. RAMSAY (1976). The rotation-vibration spectrum of HD: Wavelength and intensity measurements of the 3-0, 4-0,5-O, and 6-O electric dipole bands. Astrophys. J. 207, 663-670. MACY, W., AND W. H. SMITH (1978). Detection of HD on Saturn and Uranus, and the D/H ratio. Astrophys. J. 222, L73-L75. MARGOLIS,J. S., AND G. E. HUNT (1973). On the level
of H, quadrupole absorption in the Jovian atmosphere. Icarus 18,593-598. MICKELSON, M. E., L. E. LARSON, AND J. T. TRAUGER (1977). A Jovian methane abundance based on newly identified lines. BAAS, 9, 478. SATO, M., AND J. E. HANSEN (1979). Jupiter’s atmospheric composition and cloud structure deduced from absorption bands in reflected sunlight. J. Atmos. Sci. 36, 1133-1167. TRAFTON, L. M. (1977). Saturn: Long-term variaation of HZ and CH4 absorptions. Zcarus 31, 369384.
TRALJGER,J. P., M. E. MICHELSON,AND L. E. LARSON (1978). Laboratory absorption strengths for the H (4-O) and (3-O) S(I) lines. Astrophys. J. 225, L157-L160.
52, 54-61 (1982)
On the C/H and D/H Ratios in the Atmospheres T. ENCRENAZ Observatoire
AND
de Meudon,
Received December
of Jupiter
and Saturn
M. COMBES
92190 Meudon,
France
16, 1981; revised May 19, 1982
Using a method defined in a previous paper [M. Combes and T. Encrenaz, Icarus 39 1-27 (1979)], we reestimated the C/H ratio in the atmospheres of Jupiter and Saturn by the measurements of the weak visible CHI bands, the CH, 3q band, and the (3-O) and (4-O) quadrupole bands of Hr. In the case of Jupiter we conclude that the C/H ratio is enriched by a factor ranging from 1.7 to 3.6 relative to the solar value. In the case of Saturn, our derived C/H value ranges from 1.2to 3.2 times the solar value. The Jovian D/H ratio derived from this study is 1.2 x 10m5< D/H < 3.1 x 10m5.The value derived for the D/H ratio on Saturn is not precise enough to be conclusive.
INTRODUCTION
In spite of the remarkable results obtained on the composition of Jupiter and Saturn atmospheres from the Voyager data, there is still some uncertainty in the determination of some elemental and isotopic ratios such as C/H and D/H. In the case of Jupiter, before Voyager, results on C/H obtained from various methods ranged from a slight enrichment (Combes and Encrenaz, 1979; Encrenaz et al., 1980) to an enrichment by a factor of 3 to 5 (Cochran, 1977; Sato and Hansen, 1979; Buriez and de Bergh, 1980). The most recent determination (Gautier et al., 1981), using the Voyager IRIS data in the red wing of the CH4 uq band, concludes to an enrichment by a factor of 2.07 5 0.24 relative to the solar value. In a study by Gautier et al. (1981), as well as in the present work, the solar C/H value is taken as equal to 4.7 x 10P4, following Lambert’s (1978) determination. In the case of Saturn, the C/H value derived from scattering models ranges from 2 to 6 times the solar value (Buriez and de Bergh, 1981). Concerning the D/H ratio on Jupiter, recent determinations using the CH,D/H2 ratio derived from groundbased and Voyager IRIS data have led to a D/H ratio in the range 2-3 X 10M5(Encrenaz et al., 1980; Kunde et al., 1981; Drossart et al., 1982). In the case of 54 0019-1035/82/100054-08$02.00/O Copyright 0 1982 by Academic Press. Inc. All rights of reproduction in any form reserved.
Saturn, the first D/H determination using HD and Hz lines was made by Macy and Smith (1978), who derived a value of 5.5 * 2.9 x 10e5. More recently, a different estimate of D/H on Saturn was made by the use of CH,D lines: from near-ir spectra of Saturn, de Bergh ef al. (1981) derived a much lower D/H value (D/H < 1.25 x 10es). One of the various causes of uncertainty is the laboratory measurement of the absolute intensity of the hydrogen quadupole lines. In the case of the (4-O) band, in particular, two laboratory measurements (Bergstrahl et al., 1978; Trauger et al., 1978) found for the S1(4-0) line an absolute intensity significantly smaller than the theoretical determination of Dalgarno et al. (1969); this value was used in the study of Combes et al. (1978) and Combes and Encrenaz (1979). However, a more recent laboratory measurement by Brault and Smith (1980), using improved laboratory data, concludes to a S,(4-0) intensity in good agreement with the theory. This new result has important consequences for the determination of both C/H and D/H on Jupiter and Saturn. In particular, it can be foreseen that the method Combes and Encrenaz (1979) used with the new H,(4-0) laboratory measurement of Brault and Smith (1980) will lead to a Jovian C/H ratio in good agreement with the recent C/H result ob-
C/H AND D/H ON JUPITER AND SATURN
tained by Voyager on Jupiter (Gautier et al., 1981). In this paper, we first reapply the method defined in Paper I (Combes and Encrenaz, 1979) to the case of Jupiter, with three important improvements: (1) the new CH4 laboratory and planetary data of Lutz et al. (1981) have been taken into account; (2) the new measurement of the Sr(4-0)H2 quadrupole line obtained by Brault and Smith has been used; (3) Hz quadrupole line collision narrowing has been analyzed on the basis of Galatry’s profiles, as calculated by James (1969). Then we study how the method defined in Paper I can be applied to Saturn, and we consider the case of C/H and D/H. JUPITER
The principles of the method described in detail in Paper I can be summarized as follows. In most of the cases, the apparent abundances derived from the reflecting layer model (RLM) for two different species cannot be directly ratioed in order to obtain a reliable abundance ratio of the two species, because the scattering processes are likely to be different for the two lines or bands used for determining the apparent abundances. For this reason, we selected a set of four conditions which determines the choice of pairs of lines (or bands) of two different species, so that the scattering processes are necessarily the same for both lines. These four conditions are (I) the two lines or bands have to be chosen in the same spectral range; (2) the two lines or bands must have the same depth on the planetary spectrum; (3) the ratio to be measured must be constant with height; (4) the two absorption coefficients must have the same dependence on temperature and pressure. As discussed in detail in Paper I, the number of ideal cases for which spectroscopic data exist is very limited (12C/13C,D/ C); then, in order to extend our method to other abundance ratios, we had to consider some possible departures from some of these conditions. It has been shown (see Paper I> that two conditions are specially
55
important: condition 2 (same depth of the two lines or bands) and condition 3 (homogeneously mixed constituents). As a consequence, the case of C/H was considered in Paper I, in spite of the strong departure from condition 4 due to the pressure narrowing of the H2 lines. In what follows, we reconsider the determination of C/H on Jupiter with our method, taking into account that some uncertainty may come from the departure from condition 4. Figure 1 shows the apparent abundance of CH4 on Jupiter as a function of the depth of the CH4 bands in the laboratory spectrum. This figure is similar to Fig. 3 of Paper I, except that the recent laboratory data of Lutz et al. (1981) have been taken into account. In particular, following Lutz et al. (1981), the 6825-A band has been withdrawn, because, according to Lutz et al., some other absorber is possibly responsible for part of the absorption. It can be seen that the shape of the curve in Fig. I is in agreement with the theoretical curve that we derived from McElroy’s calculations (1969) for a homogeneous scattering model with isotropic scattering (Fig. 2). In particular, the “plateau” shown for the weak
I
0.97
I -6
I
-”
-5 -4 Log (S,/17,,)(cm-Am)-'
.
-3
FIG. 1. Apparent abundance of CH4 on Jupiter, defined as ACH4 = (mylS,,)log [I/( I - p)] (p = depth of the Jovian line or band) as a function of S&y, measured in the laboratory. (SO = Absolute intensity of the CH4 line; y,, = half-width of the CH, line.) This apparent abundance is in fact the abundance derived with the RLM assumption. The data include the 3v, points at 1 .I km for log (S&r) > -5, taken from Lecacheux et al. (1976), the visible CH, bands taken from Lutz et al. (1976, 1981), and the measurement of Mickelson et al. (1977). This figure is similar to Fig. 3 of Paper I, except that the laboratory data have been updated.
56
ENCRENAZ
RLM
Curve
of
growth
AND COMBES
results is the use of the new laboratory determination of S,(S,(4-O)), which increases our previous result of C/H (see Paper I) by approximately 2. From Fig. 3 we derive 300 < p < 600
for the (4-0)Si line
and 250 < p
for the (3-0)Si line.
The first set of unequalities I
I
0.01
0.1
I 1
I 10
8.3 x 1O-4 < C/H < 1.7 x 1O-3
w
FIG. 2. Apparent abundance as a function of the absorption coefficient at the center of a Lorentz line, estimated from McElroy (1969) calculations. The abscissa unit is w = u&u + k), where o and k are the scattering coefficient and the absorption coefficient in the continuum, respectively. The single-scattering albedo in the continuum is w, = u/(u + k) = 0.99. The related curve of growth departs from linearity for w > 0.01, while for a pure absorbing atmosphere (RLM, wc = 0) the transition from linear to square-root regime occurs only for u’ > 1.
bands [S/n-y < 5 x 10m6(cm.Am)-I] seems to correspond to the horizontal part of the theoretical curve ((Y&U + k) < 0.01) for which the absorption coefficient is negligible compared to the scattering coefficient. Table I summarizes the data included in our calculations and the quantities used for the determination of the C/H ratio. A basic limitation comes from the variations of the H2 quadrupole line intensities, especially for the &(3-O) line. We took mean values of these quantities with appropriate error bars, following the analysis of Margolis and Hunt (1973). In the case of CH4, the intensities of the Jovian bands seem less variable with time (Lutz et al., 1976, 1981). The CH, data at 1.1 p,rn, which are used for the C/H determination, refer, as in the case of the Hz lines, to the center of the disk (q = 2.1; see Paper I). Figure 3 shows our new determination of C/H on Jupiter using the quantities calculated in Table I. The technique used for building the figure and deriving the final range of p values is fully described in Paper I. The main difference with our previous
implies
C
i!Hv1 = 1.2:;:;
x 10-3 . )
Using Lambert’s (1978) determination the solar C/H ratio our result implies
of
Using a previous D/C determination given in Paper I (1.0 X lo-’ < D/C < 2.7 x 10m2)and combining quadratically the error bars we derive for D/H 1.2 x lop5 < D/H < 3.1 x 10p5.
-.-.
O.’ -
4-0
006
--g---
-5I Log I @/IT
y. ) , Log ( pZ&’
-4 ky
-3
I
FIG. 3. Determination of the C/H ratio on Jupiter by a comparison of our ACH4 curve to the (4-O) and (3-O) quadrupole lines of H,. The dashed line represents a least-squares fit of A(CH,) points. ACH4 and A,, are in km-Am, SOCWnyo and .S,Wky are in (cm-Am)-‘. The H2 observational data are indicated by the two sets of horizontal lines. In each case, the curve pMEAS = plNITIALdefines the points for which the p ratio read on the ordinates (AH21ACH4)is equal to the p ratio read on the abscissae [( SOCH4 Inyc& .S,,,,/ k-yHZ)]. The intersections of these two curves with the error bars of the measurements give the possible range of p values on Jupiter. See Paper I for more details on the method.
_
3.3 x 10-n 20 *4 Average 1963-1972 2.0 (Center of disk)
22.5 + 5 66 +5
3.5 x 10-7 74 r 30
Average 1963-1972 2.0 (Center of disk)
145 t 85 51 ? 30
[(cm-Am)-‘] f
2.5 (Central meridian) 30 2 8 75 +- 20
x 10-s
2.5 (Central meridian) 140 2 80 42 2 24
3.3
x 10-r
26 ~fr6 Average 1970-1975
x IO-’
2.1
1.59 x 10-g
-1.0
130
0.6367
S,(4-0)
72 t 30 Average 1970-1975
3.6
1.6 x IO-*
1.34 x 10-s
-1.0
130
0.8150
S,(3-0)
Saturn
a.6 Mean temperature and pressure of the planetary atmosphere in the region of line formation. eAbsolute intensity of the Hz line, at the temperature of line formation. d Half width of the Hz line. e Absorption coefficient of the H2 line at the central frequency (see Combes and Encrenaz, 1979). f Equivalent width of the H2 line on the planetary spectrum. 8 Air mass factor. h Apparent abundance of HZ in the planetary atmosphere, derived in the reflecting layer model approximation.
S,,qA (m cm-l) A (km-Am)h
Time of observation ng
W (m cm-‘)’
x 10-r
S$dky
2.2
1.7 x 10-z
IO-9
y (cmm’)d
1.68 x
-1.0
1.40 x 10-g
-1.0
P (atm)b
0.6367 150
S,(4-0)
SaH2(cm-i/cm.Am)’
0.8150 1.50
TW’
w
S,(3-0)
Jupiter
TABLE I
This paper This paper
Trafton (1977)
Margolis and Hunt (1973)
Combes and Encrenaz (1979) This paper Combes and Encrenaz (1979) This paper After Trauger et al. (1978) After Brault and Smith (1980) This paper After James (1969) This paper After Margolis and Hunt (1973) After Trafton (1977)
References
Y
ENCRENAZ AND COMBES
58
A,,_
SATURN
Figure 4 shows the apparent CH4 abundance for Saturn as a function of the depths of the CH4 lines or bands. The visible data were taken from Lutz et al. (1976, 1981). In the case of the 3u3 CH4 band at 1. I urn, we limited our study to the CH4 lines having a well-known temperature dependence, i.e., the J multiplets of the 3~ band. Following Lecacheux et al. (1976) we assumed a temperature of 130°K for the region of line formation on Saturn; according to Hanel et al. (1981) the pressure at this level is close to 1 atm. As shown in Fig. 4, the general shape of the ACHY curve looks similar to the Jupiter curve. It can be noticed that the ACH4 curve for Jupiter and Saturn appears basicaliy different from the ACH4 curve for Uranus and Neptune (Encrenaz and Combes, 1982), implying different scattering properties of the atmospheres. In Paper I we discussed in detail which abundance ratios could be derived by our method. It was shown that, in the case of Jupiter, the uncertainty due to a departure from the four ideal conditions was still acceptable for C/H so that a C/H ratio could be derived. In the case of Saturn, the ex-
?Ac,Jkm-Am) 1.0.
05-
f
* .. . O.?_T
I -6
I -5
I -4
-3
Log ( S~H4/lro) (cm-Ad’
FIG. 4. Apparent abundance of CH4 on Saturn as a function of S/.rry. The data include the 1. I-pm points [R(4), R(l), R(O), R(3), at log (S/my) > -41 taken from Lecacheux et al. (1976) and the visible bands at CH, taken from Lutz et al. (1976, 1981). The n factor is equal to 2.5.
, A,)
x IO3 1
0.4
0 H
2
,‘r
9
0.2 t
1
4_o
-6
+__k_3_o -4
-5
Log(S,CH4/rT, ) , Log(p+/
FIG. 5. Determination of parison of our A,,, curve to pole lines of H,. The dashed squares fit of the ACH4points A,, are in km-Am, SoWiny, Am))‘. The method is the Fig. 3.
kr)
C/H on Saturn by a comthe (4-O) and (3-O) quadrucurve represents a leastshown in Fig. 4. ACH4and and SoHz/ky are in (cmsame as that described in
petted line formation level is approximately at the same pressure level as for Jupiter (-1 atm), so that the method can also be used for determining the C/H ratio of Saturn; in contrast, for Uranus and Neptune, where the formation level occurs at a much higher pressure, the departure from condition 4 due to collision narrowing and pressure shift of the Hz lines cannot be neglected, so that our method cannot be used for a determination of C/H on these planets (Encrenaz and Combes, 1982). The numbers used in our calculations are listed in Table I. As for Jupiter, a major source of uncertainty comes from the variability of both the Hz intensities and some of the CH4 band intensities on the Saturn spectra (Trafton, 1977). The error bars on %’ take into account these uncertainties. For the H2 data, as for the CH, data, the r) factor is 2.5, so that both sets of data refer to the same portion of Saturn’s disk. As for Jupiter, most of the information comes from the Hz S,(4-0) line. Figure 5 shows our determination of C/H on Saturn, following the technique described in Paper I. The results shown in Fig. 5 are 330 < p < 800 250 < p
from the (4-O) band, from the (3-O) band.
C/H AND D/H ON JUPITER AND SATURN Our conclusion
is thus
330 < p < 800 or 6.2 x 1O-4 < (C/H)I, < 1.5 x 10-3, which implies, assuming Lambert’s value for the solar C/H, 1.2(C/H)o < (C/H)r, < 3.2 (C/H). ((C/H)r, = l.O$j
(1978)
59
D/C value derived on Jupiter (1 to 2.7 x lo-*; see Paper I) and on Uranus [<6 x 10m3;Encrenaz and Combes, (1982)J by the same method. Using our C/H determination on Saturn, and adding the error bars quadratically, we obtain a very high mean value for the H/D abundance ratio on Saturn: D/H = S+g x 10-j
x 10-3).
In conclusion, the C/H ratio seems to be approximately equal on Jupiter and Saturn. Both planets show a carbon enrichment, by a factor about 2 to 3, relative to the Sun. In order to estimate the D/H ratio on Saturn, we used our method with the HD observation of Macy and Smith (1978). These authors measured the HD(S-O)R(O) line and derived a D/H value by comparing their HD abundance to the H2 abundance measured from the (4-O)S, line. As for Jupiter, we first estimate D/C by using the HD observation and the A(CH4) curve. The following numbers are used: S~(HD)S_~ = 2.8 x 10m7 cm-‘/cm.Am at 130°K (after McKellar et al., 1976). Assuming a pressure of 1 atm, which is consistent with the atmospheric profiles of Hanel et al. (1981), the HD line halfwidth is y = 7 x 10m2cm-‘. The apparent HD abundance is A(HD) = 0.014 + 0.006 km.Am (Macy and Smith, 1978). The abscissa of the HD point in the (S/ ITS) scale is thus 1.2 X 10e6 (cm.Am))‘. As shown in Fig. 4, the abscissa corresponds to the horizontal plateau of the A(CH4) curve. In the region, we estimate A(CH4) = 450 + 100 m-Am. Thus we can derive the HD/CH4 ratio by simply taking the ratio of the apparent HD and CH4 abundances, 0.036 < HD/CH < 0.14 or D/C = 0.08 -+ 0.05. This value is significantly larger than the
or 2 x 10-j < D/H < 1.5 x 10-4. This value is larger than the estimate obtained by de Bergh et al. (1981) from the study of near-ir CH3D bands (D/H < 1.25 x 10m5).This value is also larger than the previous D/H estimate by Macy and Smith (1978), but this only comes from the reevaluation of the strength of the H2 Si(4-0) line; in the present case, the RLM estimate and our method give almost the same result, because the A(CH4) variation is small between the two abscissa values of Slay corresponding to the HD R0(5-0) and the H2 S1 (4-O) lines. CONCLUSION
Table II summarizes the most recent C/H and D/H results obtained on Jupiter and Saturn from visible and ir data using various methods. The conclusions of the present study are the followings: (1) the C/H ratio seems to be approximately equal in the atmospheres of Jupiter and Saturn. In both cases, the C/H ratio is enriched with respect to the solar value by a factor of about 2 to 3. This conclusion is different from the conclusion of Paper I. In the case of Jupiter, this result is in good agreement with the recent determination based upon the Voyager IRIS data (Gautier et al., 1981), implying an enrichment by a factor of 2.07 + 0.24. On the other hand, the reevaluation of our C/H value, due to the change in the measurement of the absolute strength of the H2 S,(40) line, gives a better agreement with the C/
ENCRENAZANDCOMBES TABLE 11 RECENT C/H
AND
D/H DETERMINATIONS ON JUPITER AND
SATURN
Saturn
Jupiter
Ground-based ir spectra (CH, yq band-g.5 km) IRIS (CHI Y.,band-8 pm) Scattering models (CH, 3v3-1. 1 pm) This work (visible + 1.1 p.m)
Ground-based ir spectra (CH2D Yeband-g.6 km) IRIS (CH,D Yeband-g.6 pm) + vZ band-4.5 pm) IRIS (CH3D Yeband-4.5 km) Scattering models (CH,D l-2 km) This work
C/H 110-3 (Encrenaz et al., 1980) 0.97 * 0.11 x 10-3 (Gautier et al., 1981) 1.3 -t 0.6 x IO-’ (Buriez and de Bergh, 1980) 1.2’8: x 10-3
2.0 2 1.0 x 10-3 (Buriez and de Bergh. 1981) 1.0’8: x 1om3
D/H 14 x 10-s (Encrenaz et al., 1980) 3.0’1:, x 10-S (Kunde er al., 1981) 1.8$$ x 10ms (Drossart et al., 1982) 2.0:;e x IO-’
H determination derived from the 3u3 CH4 band using scattering models [(C/H)11 = 1.5-4 x (C/H)o] (Buriez and de Bergh, 1980). In the case of Saturn, our result is in marginal agreement with Buriez and de Bergh’s (1981) estimate [(C/H),, = 2-6 x (C/H)O], but still compatible if we consider the error bars. (2) Concerning the Jovian D/H ratio, our value (1.2-3.1 x 10m5) is consistent with various other studies using the CH3D bands in the infrared spectrum of Jupiter. From ground-based observations at 8.6 pm, Encrenaz et al. (1980) derived a D/H upper limit of 4 x 10m5. Using the Voyager IRIS data at 5 and 8.6 p,rn, Kunde et al. (1981) found a D/H ratio ranging from 2 x 10-j to 4.5 X 1O-5. A similar estimate is given by Drossart et al. (1982) and Bjoraker et al. (1981). The D/H ratio derived on Jupiter is in reasonable agreement with the values measured in the local interstellar medium (Laurent, 1978) and with the value expected for the Primordial Nebula (Geiss
-
Cl.25 x 10-5 (de Bergh et a/., 1981) <1.5 x IO-4
and Reeves, 1972; Geiss and Bochsler, 1979). Concerning Saturn, the D/H value found in the present study appears to be questionable. More measurements of visible HD lines are certainly needed to confirm this result. REFERENCES BERGSTRAHL,J. T., J. S. MARGOLIS AND J. W. BRAULT (1978). Intensity and pressure shift of the H,(4-O)S, quadrupole line. Asrrophys. J. 224, L39-L41. BJORAKER,G., U. FINK, H. P. LARSON, AND V. KUNDE (1981). Abundance for Jovian belt regions from 5~ measurements. BAAS 13, 735-736. BRAGG, S. (1981). Ph.D. thesis, Washington University, St. Louis, MO. BRAULT,J. W., AND W. H. SMITH (1980). Determination of the H, 4-O S(1) quadrupole line strength and pressure shift. Astrophys. J. 235, L177-L178. BURIEZ, J. C., AND C. DE BERGH(1980). Methane line profiles near 1.1~ as a probe of the Jupiter cloud structure and C/H ratio. Astron. Astrophys. 83, 149-162. BURIEZ, J. C., AND C. DE BERGH (1981). A study of the atmosphere of Saturn based on methane line profile near 1.1 t.~.Astron. Astrophys. 94, 382-390.
C/H AND D/H ON JUPITER AND SATURN, COCHRAN,W. D. (1977). Jupiter: An inhomogeneous atmospheric model analysis of spatial variations of the H,(4-0) S, line. Icarus 31, 325-347. COMBES,M., T. ENCRENAZ,AND T. OWEN (1978). On the abundance of deuterium in Jupiter’s atmosphere. Astrophys. .I. 221, 378-382. COMBES,M., AND T. ENCRENAZ(1979). A method for the determination of abundance ratios in the outer planets. Application to Jupiter. Icarus 39, l-27. DALCARNO,A., A. C. ALLISON, AND J. C. BROWNE (1969). Rotation-vibration quadrupole matrix elements and quadrupole absorption coefficients of the ground electronic states of H,, HD and DZ. J. Atmos. Sci. 26, 946-95 1. DE BERCH, C., B. L. LUTZ, G. W. LOCKWOOD, T. OWEN, J. BRALJLT,AND J. C. BURIEZ (1981). Detection of CH,D and measurements of the CH,D/CH, ratio on Titan and Uranus. BAAS 13, 703. DROSSART,P., T. ENCRENAZ,V. KUNDE, R. HANEL, AND M. COMBES (1982). An estimate of the PH?, CH,D and GeH, abundances on Jupiter from the Voyager IRIS data at 4.5 pm. Icarus, in press. ENCRENAZ,T., AND T. OWEN (1973). New observations of the hydrogen quadrupole lines on Saturn and Uranus. Asfron. Astrophys. 28, 119. ENCRENAZ,T., M. COMBES,ANDY. ZEAU (1980). The spectrum of Jupiter between 8 and 9 microns : Estimates of the Jovian C/H and D/H ratios. Astron. Astrophys.
84, 148-153.
ENCRENAZ,T., AND M. COMBES(1982). On the D/C ratio in the atmosphere of Uranus. Icarus 49, 2734. FINK, U., AND M. J. S. BELTON (1979). Collisionnarrowedcurves of growth for HZ applied to new photoelectric observation of Jupiter. J. Atmos. Sci. 36, 952-962. GAUTIER,D., A. LACOMBEAND I. REVAH (1977). Saturn: Its thermal profile from infrared measurements. Astron. Astrophys.
61, 149-153.
GAUTIER, D., B. BEZARD, A. MARTEN, AND J. P. BALLJTEAU(1981). The C/H ratio in Jupiter from the Voyager experiment. BAAS 13,738. GEISS, J., AND H. REEVES (1972). Cosmic and solar system abundances of deuterium and helium 3. Astron. Astrophys. 18,126-132. GEISS, J., AND P. BOCHSLER(1979). On the abundances of rare ions in the solar wind. In Proceedings,
4th
Solar
Wind Conference,
Burghausen.
Springer-Verlag, Berlin/Heidelberg/New York. HANEL, R., B. CONRATH,M. FLASAR, V. KUNDE, W. MAGUIRE,J. PEARL, J. PIRRAGLIA,R. SAMUELSON, L. HERATH, M. ALLISON, D. CRUIKSHANK, D. GAUTIER, P. GIERASCH, L. HORN, R. KOPPANY, AND C. PONNAMPERUMA(1981). Infrared observations of the Satumian system from Voyager I. Science 212,192-200. JAMES, T. C. (1969). Calculations of collision narrow-
61
ing of the quadrupole lines in molecular hydrogen. J. Opt. Sot. Amer. 59, 1602-1606. KUNDE, V., R. HANEL, W. MAGUIRE, D. GAUTIER,J. P. BALUTEAU, A, MARTEN, A. CHEDIN, N. HusSON, AND N. SCOTT (1981). The lower atmosphere composition of Jupiter’s north equatorial belt from Voyager 1 IRIS. BAAS 13, 735. LAMBERT,D. (1978). The abundances of the elements in the solar photosphere. VIII. Revised abundances of carbon, nitrogen, and oxygen. Mon. Not. Roy. Astron. Sot. 82, 249-272.
LAURENT, C. (1978). L’abondance
du Deuterium interstellaire a partir dur satellite Copernicus et ses implications astruphysiques. These de Doctorat
d’Etat, Universite de Paris VII. LECACHEUX,J., C. DE BERGH, M. COMBES,AND J. P. MAILLARD(1976). The C/H and 1ZCH41r3CH4 ratios. in the atmospheres of Jupiter and Saturn from 0.1 cm-’ resolution near infrared spectra. Astron. Astrophys. 53, 29-33.
LUTZ, B. L., T. OWEN, AND R. D. CESS (1976). Laboratory band strengths of methane and their application to the atmospheres of Jupiter, Saturn, Uranus, Neptune and Titan. Asrrophys. J. 203, 541-551.
LUTZ, B. L., T. OWEN, AND R. D. CESS (1981). Laboratory band strengths of methane and their application to the atmospheres of Jupiter, Saturn, Uranus, Neptune, and Titan. II. The red region 6000-7600 A. In press. MCELROY,M. B. (1969). Atmospheric composition of the Jovian planets. J. Atmos. Sci. 26, 798-812. MCKELLAR,A. R. W., W. GOETZ, AND D. A. RAMSAY (1976). The rotation-vibration spectrum of HD: Wavelength and intensity measurements of the 3-0, 4-0,5-O, and 6-O electric dipole bands. Astrophys. J. 207, 663-670. MACY, W., AND W. H. SMITH (1978). Detection of HD on Saturn and Uranus, and the D/H ratio. Astrophys. J. 222, L73-L75. MARGOLIS,J. S., AND G. E. HUNT (1973). On the level
of H, quadrupole absorption in the Jovian atmosphere. Icarus 18,593-598. MICKELSON, M. E., L. E. LARSON, AND J. T. TRAUGER (1977). A Jovian methane abundance based on newly identified lines. BAAS, 9, 478. SATO, M., AND J. E. HANSEN (1979). Jupiter’s atmospheric composition and cloud structure deduced from absorption bands in reflected sunlight. J. Atmos. Sci. 36, 1133-1167. TRAFTON, L. M. (1977). Saturn: Long-term variaation of HZ and CH4 absorptions. Zcarus 31, 369384.
TRALJGER,J. P., M. E. MICHELSON,AND L. E. LARSON (1978). Laboratory absorption strengths for the H (4-O) and (3-O) S(I) lines. Astrophys. J. 225, L157-L160.