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.Unfortu-nately, he realized, its structural weakness, as a resultof lacking metal in real quantity, made it impractical for use except whereprotection against heat and radia-tion were paramount considerations.Lucky was a mile into the Sun-side now and not conscious of undue heat.This did not surprise him.To stay-at-homes who confined their knowledge ofspace to the sub-etheric thriller shows, the Sun-side of any airless planetwas simply a solid mass of undeviating heat.This was an oversimplification.It depended on how high the Sun was in thesky.From this point on Mer-cury, for instance, with only a portion of the Sunabove the horizon, comparatively little heat reached the sur-face, and thatlittle was spread over a lot of ground as the radiation struck almosthorizontally.The  weather changed as one went deeper into the Sun-side and finally, whenone reached that portion where the Sun was high in the sky, it was everythingthe sub-etherics said it was.And besides, there were always the shadows.In the absence of air, light andheat traveled in a straight line.Neither could reach within the shadow exceptfor small fractions which were reflected or radiated into it from neighboringsunlit portions.The shadows were there-fore frosty cold and carbon blackthough the Sun was ever so hot and bright.Lucky was growing more aware of these shadows.At first, after the upper lineof Sun had appeared, the ground had been almost all shadow with onlyocca-sional patches of light.Now, as the Sun rose higher and higher, thelight spread and coalesced until the shadows were distinct things hoveringbehind boulders and hills.At one time Lucky deliberately plunged into the shadow of a rise of rock ahundred yards across, and it was as though for a long minute he were back onthe dark-side.The heat of the Sun, which he had scarcely noticed while itbeat upon him, became evident by its decrease in the shadow.All around theshadow the ground glimmered brightly in sunlight, but within the shadow hisPage 54ABC Amber Palm Converter, http://www.processtext.com/abcpalm.htmlsuit-light was necessary to guide his steps.He could not help noticing the difference in the surfaces that were in theshadow from those in the light.For on the Sun-side, at least, Mercury didhave a kind of atmosphere.Not one in the Earthly sense, no nitrogen, oxygen,carbon dioxide, or water vapor, noth-ing like that.On the Sun-side, however,mercury would boil in places.Sulfur would be liquid and so would a number ofvolatile compounds.Traces of the vapor of such substances would cling toMercury s superheated surface.These vapors froze out in the shadows.This was brought forcibly to Lucky s mind when his insulated fingers brushedover the dark surface of one outcropping and came away smeared with a frozenhoar of mercury, glittering in his suit-light.It changed quickly intoclinging liquid droplets as he emerged into the Sun and then, more slowly,evaporated away.Slowly, the Sun seemed to be getting hotter.That did not worry Lucky.Evenif it grew uncomfortably hot, he could always dodge into a shadow to cool offwhen necessary.Short-wave radiation was perhaps a more important consideration.Luckydoubted even that was serious in this short-term exposure.Workers on Mercuryhad a horror of radiation, because they were continually ex-posed to smallamounts.Lucky recalled Mindes s em-phasis on the fact that the saboteur hehad seen had remained standing in the Sun.It was natural that Min-des shouldbe disturbed at that.When exposure was chronic any lengthening of the time ofexposure was foolish.In Lucky s own case, however, exposure would beshort-term he hoped.He ran across patches of blackish ground that stood out somberly againstMercury s more general reddish gray.The reddish gray was familiar enough.Itresem-bled the soil of Mars, a mixture of silicates with the addition of ironoxide, which gave it that ruddy tinge.The black was more puzzling.Wherever it was, the ground was definitelyhotter, since black absorbed more of the Sun s heat.He bent as he ran and found the black areas crumbly rather than gritty.Someof it came up on the palm of his gauntlet.He looked at it.It might begraphite, it might be iron or copper sulfide.It might be any of a number ofthings, but he would have bet on its being some variety of impure ironsulfide.He paused in the shadow of a rock, finally, and took stock.In an hour and ahalf, he estimated he had traveled some fifteen miles, judging from the factthat the Sun was just about entirely above the horizon now.(At the moment, hewas more interested in sipping sparingly at the suit s supply of liquidnutrient mixture than in estimating distance, however.)Somewhere to the left of him were cables of Mindes s Project Light.Somewhereto the right of him were others.Their exact location did not matter [ Pobierz całość w formacie PDF ]