I turned my head quickly toward the screen. There was just the flimsy outline of something there; something barely perceptible to the waves that scanned the path ahead of the ship. But whatever it was, it was in our path and it was very large. A cloud, maybe--only clouds don't show on radar. "Meteors!" screamed Spartan. "Heaven help us! It's a meteor cloud!" He pushed me aside and sprang to the controls. At the same time, he touched the emergency button, setting off a shrieking siren alarm. _Chapter 7_ Except for two or three meteor clouds which the earth plows through on its annual turn around the sun, the number and location of these in the solar system are unknown. They are not clouds in the sense that they hang like a heavy mist and obscure objects behind them. They are so thin and tenuous that if thousands of meteors did not shower on the earth when it goes through their midst, we would be unaware of their presence in space. The cloud ahead of us was, possibly, half a million miles in diameter, making it rather small. The Perseids and Leonids, for example, may extend completely around the sun in the orbit of a disintegrated comet. Very few of the meteors are larger than a grain of sand and they are so widely scattered that all of the meteors in a cubic mile of space might be packed into a teacup. However, a few of them might be as large as a teacup and, very rarely, one might be as big as a house. For a planet like the earth to plow through a cloud of meteors, there is little danger. For one thing, most of the meteors are vaporized as they strike the upper atmosphere. Only a few ever reach the earth and there have been only a couple of cases on record where a human being has been harmed by a meteorite. But the Jehad had no atmosphere to shield it from meteors. True, we were equipped with double walls capable of vaporizing a meteor up to a quarter of an inch in diameter. And we had methods of minimizing the danger of larger meteors--leakproof fluid in the walls, airtight bulkheads dividing the ship into segments, spacesuits, and a reserve supply of oxygen. But there was always that extreme chance of striking a big fellow, which would cancel out all our defenses. This cloud ahead of us certainly held a few that size. Had Axel and I not been so interested in the signals from Mars, we might have spotted the meteors several minutes sooner. Our ship was now traveling close to 30,000 miles an hour, however, and those minutes had eaten up precious distance in which we might have maneuvered the craft out of danger. We were less than an hour's run from the fringe of the cloud. The Jehad, using a very small amount of power to accelerate its huge mass, could not be turned in time to avoid it.