 Why does Baron think there was something wrong with Claney's filters?
He had no stomach for mysteries, vast or trifling, and there were pressing things to think about at this time. Yet the doorman had flagged him as he came in from the street: “A thousand pardons, Mr. Baron. Across to the right was a group that Baron knew vaguely—Andean climbers, or at least two of them were. Then he settled back and waited impatiently for the intruder who demanded his time without justifying it. Presently a small, grizzled man crossed the room and sat down at Baron’s table. He was a major in the Interplanetary Service for some years and hung onto the title after he gave up his commission. Then he made the attempt on Vulcan Crater that paved the way for Balmer a few years later. “I want to make a Crossing at perihelion and I want to cross on the surface. The Twilight Lab, near the northern pole of Mercury, was the obvious jumping-off place. The setup there wasn’t very extensive—a rocket landing, the labs and quarters for Sanderson’s crew sunk deep into the crust, and the tower that housed the Solar ’scope that Sanderson had built up there ten years before. F. No permanent installation with a human crew could survive at either extreme. Sanderson built the Lab up near the pole, where the zone is about five miles wide, so the temperature only varies 50 to 60 degrees with the libration. The Major was counting on Sanderson knowing something about Mercury as well as the Sun when we camped at the Lab to make final preparations.
 Claney's face is covered in cancerous tumors.
 Claney's face is extremely sunburned.  Claney's face is twisted and brown.  Claney's face is covered in scars.  Claney's face is covered in cancerous tumors.