cn —— ATMOSPHERIC AND SURFACE PROPERTIES OF MARS, VENUS AND THE MOON The attached summaries on the atmospheric and surface properties of some of the planets were compiled by Dr. W.W. Kellogg, Head, Planetary Sciences Lepartment, The Rand Corporation, Santa Monica, California at the request of Dr. C.G. Hedén. In an accompanying letter to Dr. Hedén, Dr. Kellogg makes the following comments which should be of interest to those using the tables. At last, here are the summaries that you requested of the atmospheric and surface characteristics of Mars, Venus, and the Moon, for the use of the scientists who may be discussing the implications of contaminating these bodies. This is intended to assist you in your efforts on behalf of our Consultative Group on Potentially Harmful Effects of Space Experiments of COSPAR to organize such discussions, I hope that it will be apparent to all who use these summaries that much of the material is quite uncertain (I have tried to indicate ranges of uncertainty hers possible), and that some of the statements are based on my wh biases, or "guesses", I can explain the reasoning behind all of these guesses, but realize that some scientists might still not.entirely agree with me. Therefore, the summaries should be used with due caution. Just to emphasize this point, I have included the Earth as one of the planets under consideration, and it is significant that, even here, some of the characteristics that you called for are difficult to specify. Those who may wish a more complete review of the situations on Mars and Venus can see the. 1961 review by Carl Sagan and myself, published by the U.S. National Academy of Sciences, Washington, D.C.3; or they may await the forthcoming issue of Annual Review in Astronomy and Astrophysics, containing an updated review of the same.subject (plus Mercury) by the same authors. . As for the planet Jupiter, I left it out of my summary, in spite of the vague possibility that it might support life of some sort. We know virtually nothing about the conditions at its "surface", if it has one at all in the usual sense. Astronomers are not even sure about the conditions above its ¢loud tops, where they can make some observations. A recent review by E.c. Opik (Icarus, 1(3), pp. 200-257, 1962) attributes to the "observable atmosphere" the following percentage composition: He 97.2, Ho 2.3, Ne 0.39, CH, 0.063, A 0,042, and NH 0.0029. Presumably there could be more NH, and H20 lower in the atmosphere, but both of these tend to "snow out" at the very cold cloud level (156°K at the top) and so are not as abundant in the higher atmosphere. SUMMARY OF LUNAR AND PLANETARY SURFACE ENVIRONMENTS FOR USE IN DISCUSSION OF IMPLICATIONS OF CONTAMINATION EARTH MOON MARS VENUS LOWER ATMOSPHERE Chemical composition N,~78%,0,~21%, Ar ,CO, (?) Ny~95%,Ar~2 .5%,CO,~2% N, 80-95%,C0, 5-20%, Ar~1%,CO,~.03% or 30-40 m STP (1), H,0~.001% or less (7) or 2.4 m STP, HO 2-8x109 gm/em? H,0 0-2.5% or (afluncertain by at 2 least a factor 1-10 gm/em (variable) of two. )(1) witha a Codkor o& {eae : Pressure at surface 1013 mb at sea level <107 On» 80 to120- mb (1) 5-50 atmospheres Movement Extremely variable, with Free molecular Probably light. winds Probably very light winds mean speed about 1-5 m/ diffusion at equinox, cyclonic at surface (a guess) sec. Cyclonic storms at storm systems of mid-latitudes at all considerable inten- seasons. Most intense sity around solstice. in winter. Occasional Dust storms observed; | very strong winds in also, moving as well tropical storms as stationary white (hurricanes) and highly or yellow clouds localized vortices observed. — (tornados). TEMPERATURE AT SURFACE ‘ Maximum 320°K (50°C) 375°K 300°K (25°C) 700° -800°K (subsolar) (100°C) (equatorial noon) Mean Minimum Length of cycle at equator (day) Length of cycle at poles (year) 288°K (15°C) 230°K( -45°C) 24 hrs 1 year (Rapid change * day-to-nite) 120°K (-150°C) 27 days 1 year 210-220°K (-50 to -60°C) 180°K (-90°C) (winter pole) 24.6 hrs 687 days 600° -700°K (antisolar) ~120 days (uncertain) ~225 days (uncertain) RADIATION AT SURFACE Ultraviolet cutoff ' Visible light intensity (relative to earth) Ionizing radiation (flux of <1000£ radiation) CHEMISTRY OF SURFACE Water Salt Carbon sources Nitrogen sources ° 3000A (due to ozone) Same None 4/5 surface covered with liquid or solid water. Water-soluble salts largely unavailable at surface due to leaching by rain, except in special areas of low rainfall, Widespread, due to past and present organic processes. Ibid. no cutoff Same No cutoff, same as in space None ~ Not certain. Probably enough O, to give some attenuation at around 2500A ; also, considera- ble attenuation by Rayleigh scattering combined with absorp- tion by haze particles. co, will cause complete cutoff below about 1800A in any case. WY, Same on the average None Hoar frost on winter polar area. May be frozen water in perma- frost layer (a guess). Common water soluble salts probably generally available (a guess) Some spectroscopic evidence for organic material in dark areas 1 where seasonal welepeede eth anges also occur. ? ® - Not certain. Probabl;; 7:0 penetratiop to surfacc below 3000A due to sore.’ ozone and miltiple scattering in deep atmosphere. . Less. May be fairly dark at surface due to deep atmosphere; blue more attenuated than.near IR. None None * CHARACTER OF’ SURFACE Surface physical structure Temperature distri- bution below surface Depth of probe penetration in hard landing (max. ) TERMINAL VELOCITY OF FALL of solid dust particles (9* 2.5 gm/cm3) near the surface for a given ‘ particle radius (2) (cm/sec) Variable (sand, clay, rock, water, snow, ice, etc.) Level of uniform temp. from O to 3m below surface. ~0.1 m in hard rock, ~ m in sand and loose soil, up to 10 km in ocean. ly 10 100u 1000, Insigni- 3.1 139 ficant relative to tur- bulent transport. * Variable Average thermal conductivity much lower than terre- strial surface. Presumably very porous material over most of surface, but evidence for localized o regions with higher conduct- ivity. Possibly very porous and easily pene- trated in * places, cer- tainly some hard rock. oo - Earth. Red areas - probably sandy or dusty, limonite suggested by color and polarization er observa- tions. Dark areas - ? Hoar frost observed covering winter pole, more extensive than on Polar cap may disappearg in summer from South Pole, persists all year near North Pole. Variable. Probably like terrestrial desert (a guess). ‘ ~O.1 m in hard rock, ~4 min sand or loose soil (a guess). Jp 10 100u 1000u * 1.16 104 ~ 1840 a) Probably very hot, dry dusty surface (a guess) Some radar evidence for large irregularity like a mountain range. oo 1 10. 100. 1000u ** 1.6 9.25 75 € Notat bene: (1) (2) A recent announcement by L. Kaplan and H. Spinrad (Jet Propulsion Laboratory, Pasadena, Calif.) presented verbally at the Astrophyiscal Symposium in Liege in July, 1963 (but still unpub lished gives evidence for an increase in the CO2g content of the Martian atmosphere to about 100 m STP and a reduction in the surface pressure to less than 20 mb. This is still unconfirmed by any * other workers. The fall rates presented here were calculated especially for this chart by R. R. Rapp (RAND Corporation, Santa Monica, Calif.). Details of these calculations can be made available later for those wishing them. Note that the smaller particles (1 and 10) obey Stokes' law, except for lu particles on Mars which are in the free molecular flow regime. Particles of 100, and over obey aerodynamic drag laws on all three planets. Values for the pertinent atmospheric parameters used in these estimates are as follows: (all in ¢.g.s. units) . Mean Free Gravity Degsity Viscosity Path g t . A “3 4 -6 Earth 981 1.22x10 1.79x10 6.6x10 Mars «4333 ix10~4 1.6x10"* —gx107> 2 7 Venus 862 3x10- 3.0x107* —2..6x107 The fall rates for lu particles on Earth, Mars, and Venus are 0.016, 0.031, and 0.024 cm/sec respectively, so it is quite certain that turbulence near the ground will determine their trajectories in the air rather than their theoretical rates of fall.