Blish, James—Welcome to Mars by James Blish

Author:James Blish
Language: eng
Format: epub

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9. THE LONG BLAST

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Nanette was right. That night's sandstorm was only half an hour longer than usual, but the next morning's was better than an hour longer; and as the week wore on, the situation worsened steadily. By the end of the week, there was only about an hour around noon (and, presumably, another around midnight) when the air was quiet and clear. It was evident that the porthole would be covered shortly—and after that, perhaps the house itself.

Their only hope lay in the fact that the wind continued always to blow in the same direction—though now from the south. Both the change and its constancy baffled Dolph for quite a while, but finally he thought he saw glimmerings of an explanation.

'Look,' he said, drawing a circle on a scrap of leftover wall-paper. 'I'd be a lot surer of this if we had an outside barometer—come to think of it, it ought to be a snap to build one—but as a theory it makes sense. Say this is Mars, looking down on it at the North pole at the time we arrived—just before the equinox, when the equator is warmer than the poles, just like it is all year round on Earth. While it's like that, the air ought to circulate like it does on Earth. Here's the direction of rotation, counter-clockwise. Now—' he quickly sketched in something like a ship's propeller, it centres at the pole, its blades bent away from the direction of rotation—'that gives us a travelling wave up in the stratosphere, a jet stream, like this, going in and out towards the pole twice a day but blowing in the same direction the planet rotates. Of course that never touches the ground, but—' he put in four ovals trailing after the 'blades' of the 'propeller'—'it trails four high-pressure spots out towards the equator, and those give us our dawn and dusk winds. If we were farther north or south, say at about forty-five degrees of latitude as we were in Iowa, we'd hit low-pressure cells that would have the same effect. So that's why the weather always moves from west to east, just as it does at home.'

'Which is why the wind is blowing steadily north now,' she agreed gravely. 'Brilliant, Holmes, brilliant.'

'No, it isn't, idiot. Now winter is coming on, and winter on Mars isn't like home, because then one Martian pole is warmer than the equator—which never happens at home.' He drew another circle. 'Here's Mars in winter. Then the wind blows from one pole to the other, going along the ground from the cold pole to the warm one, and back up and over through the stratosphere. And it'll go right on like that through the solstice to the next equinox.'

She considered this in silence for a few moments.

'It makes sense, all right,' she said at last. 'And I don't think I like it, Dolph. With the wind blowing from the cold pole steadily, all the time, for nearly a year—well, it's going to be cold around here.

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