Diameter and density of Neptune
Diameter, density, and atmospheric data calculated for Neptune from 7 Apr. 1968 occultation
Levin, B. YU.↗
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Resonances in the Neptune-Pluto system
Pluto orbit integration over 4.5 million years by variation of parameters technique and confirming Neptune-Pluto orbital resonances
Benson, G. S.↗
Heat protection for atmospheric entry into Saturn, Uranus, and Neptune
Graphitic ablative heat shield fractions and forebody configurations for probe entry into atmospheres of Saturn, Uranus and Neptune
Tauber, M. E.↗
On the methane opacity for Uranus and Neptune.
The contribution of methane to the thermal opacity in the atmospheres of Uranus and Neptune is shown to be negligible. The relevance of this finding lies in the importance of knowing all the sources of thermal opacity to include in models of these atmospheres, for only then may it be possible to deduce their atmospheric structure and composition correctly.
Trafton, L.↗
Interferometer observations of Uranus, Neptune, and Pluto at wavelengths of 11.1 and 3.7 centimeters.
Visibility observations of Uranus at 8.085 GHz fit a uniform circular disk with a diameter of 3.8 (plus or minus 0.2) sec. The disk temperature of Uranus and Neptune are, respectively 189 (plus or minus 7) K and 190 (plus or minus 20) K at 8.085 GHz, and 195 (plus or minus 30) K and 201 (plus or minus 40) K at 2.695 GHz, in agreement with previous results that the microwave temperatures are higher than those expected for blackbodies in equilibrium with solar radiation. The 8.085-GHz observations yield an upper limit of 162 K for the disk temperature of Pluto.
Webster, W. J., Jr.↗
The planets Uranus, Neptune, and Pluto (1971)
Design criteria relating to spacecraft intended to investigate the planets of Uranus, Neptune, and Pluto are presented. Assessments were made of the potential effects of environmental properties on vehicle performance. Pertinent data on the mass, radius, shape, mean density, rotational pole location, and mean orbital elements for the three planets are given in graphs and tables.
Palluconi, F. D.↗
Multicolor photoelectric photometry of Neptune.
Mean opposition magnitudes at unit distance and geometric albedos obtained as functions of wavelength from multicolor photoelectric photometry observations of Neptune performed in southern France and South Africa are presented. The measurements were made in the standard UBV bands and in seven narrow bands isolated by interference filters between 0.314 and 0.627 microns.
Appleby, J. F.↗
The wavelength dependence of the albedos of Uranus and Neptune from 0.3 to 1.1 micron.
Narrow-band photoelectric photometry was made of Uranus and Neptune over a wavelength interval from 0.3 to 1.1 micron. The wavelength dependence of the geometric albedo was determined for these planets. Evidence is given that the comparison star used resembles the sun very closely in its energy distribution. It is shown that, apart from methane, another opacity source seems to be necessary in the atmospheres of these planets to explain the observed wavelength dependence of the geometric albedo for the two planets simultaneously. Radiative transfer calculations were made to determine if the previously suggested pressure-induced dipole absorptions of H2 result in a self-consistent explanation. This seems to be the case. The H2 abundance in this case is limited for both planets between 350 km amagat less than or equal to N(H2) less than 800 km amagat. This agrees with a previous determination of the H2 abundance for Uranus.
Wamsteker, W.↗
On the upper atmosphere of Neptune
We have reanalyzed the Mount Stromlo observations of the occultation of BD 17 4388 by Neptune and find that the upper atmosphere is not isothermal as suggested by Freeman and Lynga. For a pure hydrogen atmosphere, our results give a temperature of 135 K at a number density of 1000 trillion per cu cm. Above this level, the possibility of a small overall positive temperature gradient is suggested by the data. The temperature structure is complicated in detail, with local 5 to 10 K fluctuations some 10 km in extent associated with the numerous spikes in the light curve. Concentrations of helium greater than 50 per cent can probably be ruled out.
Veverka, J.↗
The upper atmosphere of Neptune - An analysis of occultation observations
An analysis of available observations of the April 7, 1968, occultation of BD-17 deg 4388 by Neptune yields upper atmosphere temperatures of about 140 K near the 5 x 10 to the 14th power per cu cm level. The temperature structure of the atmosphere at these levels is complicated and nonisothermal. Diurnal temperature variations are certainly less than 15 K between 0 and 55 deg latitude.
Rages, K.↗
Infrared measurements of Uranus and Neptune
New measurements verify that Neptune is brighter than Uranus near 20 microns and show that both planets have increasing brightness temperature with decreasing wavelength between 34 and 22.5 microns. The observations are not compatible with existing models for the atmospheres of these planets.
Rieke, G. H.↗
Observational constraints on model atmospheres for Uranus and Neptune
We have re-examined the visible and near-IR regions of the spectra of Uranus and Neptune to provide additional data for constructing atmospheric models. We find that a true continuum exists only at wavelengths below 4700 A, that the 6420 A absorption previously attributed to hydrogen is probably caused by methane, that there is no evidence for ammonia, ethylene or ethane absorptions in our spectra, and that the abundance of methane is probably much higher than previous estimates suggest. This last finding implies that the value of H/C in the atmospheres of both planets is much less than 1/10 the solar (or Jovian) value. Clear, Rayleigh-scattering model atmospheres are not compatible with the observations, but more work is needed to establish viable alternatives.
Encrenaz, T.↗
On the detection of magnetospheric radio bursts from Uranus and Neptune
Earth, Jupiter, and Saturn are sources of intense but sporadic bursts of electromagnetic radiation or magnetospheric radio bursts (MRB). The similarity of the differential power flux spectra of the MRB from all three planets is examined. The intensity of the MRB is scaled for the solar wind power input into a planetary magnetosphere. The possibility of detecting MRB from Uranus and Neptune is considered.
Kennel, C. F.↗
Laboratory band strengths of methane and their application to the atmospheres of Jupiter, Saturn, Uranus, Neptune, and Titan
This paper reports laboratory studies of the visible spectrum of methane at column densities between 0.4 and 5 km-am and confirms the identification of bands at 4410, 4590, 4860, 5090, 5430, 5760, and 5970 A as caused by methane. Detailed equivalent-width measurements at 15 different pressure path lengths are employed to determine curves of growth and band strengths for the bands at 4410, 4860, 5430, and 5760 A. Using the curve-of-growth measurements in the reduction of planetary observations, the methane abundances in the atmospheres of Jupiter and Saturn are found to be between a factor of 3 and 4 larger than previously accepted values based on the analysis of the 3 nu(3) band at 1.1 microns, while the amount on Titan is significantly less than that obtained from an analysis of the same band with the assumption of a pure methane atmosphere. The present results, when combined with the band analysis, suggest a surface pressure on Titan of at least 0.4 atm. Extrapolation of these laboratory data to observations of Uranus and Neptune lead to single-air-mass column densities of 5.8 and 7.6 km-am of methane, respectively.
Lutz, B. L.↗
Limitations to growth of microorganisms on Uranus, Neptune, and Titan
Reappraisal of the probabilistic policy toward planetary contamination by terrestrial microorganisms carried aboard space probes is suggested on the grounds that assignment of numerical probabilities to qualitatively unknown phenomena, as expressed in Phillips's (1974) formulation of the probability of contamination, is inappropriate. As an alternative, it is proposed that fundamental knowledge of the interacting nature of life on earth, interrelations between terrestrial organisms, and continuing effects of these organisms on earth's atmosphere and surface should guide the formulation of a sounder scientific quarantine policy. Simple conservative atmospheric models most favorable for life on Uranus and Neptune are examined. It is concluded that terrestrial microorganisms will not grow on either planet due to limitations of liquid water, atmospheric convection to lethal depths, the absence of energy sources and nutrients, the presence of ammonia and hydrogen, insufficient concentrations of biologically necessary ions, and the lack of a surface. The likelihood of terrestrial microorganism growth on Titan is found to be vanishingly small.
Margulis, L.↗
On the 6825 A band of methane as observed in Uranus and Neptune
A high-resolution spectrum of the series of lines near 6825 A presumably due to CH4 has been obtained for Uranus. The line spacings are in agreement with the previous observations of Owen (1966), Bergstralh (1975), and Belton and Hayes (1975) but not with the laboratory observations reported by Lutz and Owen (1976). It is proposed that the transitions identified by Lutz and Owen are not correlated one-to-one with those features observed in the planets. Wavelength differences of up to 0.8 A are found between the laboratory and planetary features, where the resolving power allows one to specify the line positions to better than + or - 0.07 A. The spectrum obtained for Neptune is in essential agreement with that for Uranus.
Gelfand, J.↗
5-20 micron observations of Uranus and Neptune
Emission features at 8 and 12 microns indicate a strong temperature inversion in the upper atmosphere of Neptune. The presence of only a weak inversion on Uranus is confirmed.
Gillett, F. C.↗