He sent off a distance-pulse and took angular measurements of the planet's disk. The ratio of polar to equatorial diameters was informative. The polar flattening said that the day lasted about thirty hours. Almost like Earth's. The equatorial diameter of 8200 miles was much like Earth's. The inclination of the axis of rotation indicated seasons--not exaggerated, but much like the seasons on the third planet of Sol. The size of the ice-caps indicated the overall planetary temperature. There were clouds. In fact, there was a cloudmass in the southern hemisphere that looked just like an Earthly tropic storm undergoing the usual changes as it went away from the equator. This was very much like Earth! And the dark masses which were seas.... * * * * * Nolan frowned. Those mud-colored patches were water. Undoubtedly. A narrow-band light filter proved it. But the areas which were neither sea nor cloud mass? There were three levels of brightness to be seen on the disk outside the polar areas. One was sea-bottom. One was cloud. The other.... Nolan fretted a little. There was something wrong. The solid ground surface of the planet was too light in color. It was such items that a person with a knack for it would notice sooner than a man without the knack. Vegetation should be more nearly midway between sea-bottom and cloud mass in color. Nolan fitted in the chlorophyll filter. On the planet of a sol-type sun, vegetation had to use chlorophyll or else. Through this filter the clouds would show, of course. They were white and reflected all colors of light. But no color that chlorophyll didn't reflect could pass through the filter. The cloud masses showed clearly. Nothing else appeared. The filters would have shown vegetation. It didn't. It said there wasn't any. Nolan stepped up the magnification. He saw other things. He didn't like them. He got some maximum-magnification pictures and interpreted them with increasing grimness.