Periasteron marked the beginning and the end of each 45-day year. It was the time when Trellwan was closest to Trell in its slightly eccentric orbit about the star, and always occurred over the same two spots on the planet's surface. The Periasteron called Far Passage occurred on the other side of the world in the middle of each Secondnight. It was heralded in Sarghad by mild storms sweeping in from the dayside, and by gradually rising temperatures that marked the beginning of Sarghad's brief spring-summer-fall.
The Periasteron called Near Passage occurred over the Nerge, the Black Desert, 2,000 kilometers to the west of the city, and was altogether different.
Trell was in the sky at that lime, just past the middle of Firstday for Sarghad's longitude. As the local temperature rocketed under the burning heat, water evaporated from the surface of the nearby sea at an accelerated rate. Clouds boiled skyward so quickly that their growth could be followed with the eye. As vast volumes of hot, wet air rushed from ground level into the chill stratosphere, they dragged in desert winds that howled across Sarghad from the mineral flats to the east
Then the rains came, violent, rattling-wind rains that turned the ocher deserts to seas of mud and flooded the streets of Sarghad. As the planet's slow rotation continued, Sarghad gradually descended into continuous night In that long night, the storm continued while temperatures plummeted.
By mid-Firstnight, some five or six standard days later, it was snowing in the mountains above the city. Most of the moisture deposited as snow fell in the mountains, and across the great ergs and glacial plains far to the north and south. The equatorial desert around Sardghad froze solid as temperatures plummeted to 50 degrees or more below zero, and high in the mountains, short-lived glaciers grew.
The snow lay heavy among the jagged range peaks. There were places where seismic shocks and the repeated cycles of snow, freezing, heat, and falling meltwater had cracked open the mountains, laying bare ancient, hidden faults, caverns, and the wellsprings of river leading down to the sea. Hot mineral springs rising within the caves opened caverns beneath glistening roofs of ice. Within these caverns' sheltering heat, there was the steadily echoing plip-plip-plip of snow melting and trickling down the fantastic dagger shapes of stalactites.
Far Passage occurred in mid-Secondnight. There were storms then, mostly wind- and duststorms born on warm winds from the antipodes, and the temperature began to rise. By mid-Thirday, the temperature was above freezing, and still climbing. Whole mountains of rapidly accumulated ice and packed snow began melting.
In places, the melt was catastrophic.
Thunder Rift was the largest and deepest of the network of fault-rifts and caverns in the mountains north of Sarghad. During cold periods, it was completely roofed over by ice hundreds of meters thick. From early Thirday until well into Firstday, meltwater created an icy cataract. The booming, cascading, white-raging waterfall fell by many-branching paths worn through ice and rock into a deep-cleft lake, from which spray rose like a cloud. During warmings periods, that cloud spray hung above the V-shaped notch that marked the Rift as seen from the city plain, and the thunder of the waters could be distantly heard above the incessant murmur of street merchants and vendors.
Grayson had discovered the Rift shortly after Carlyle's Commandos had arrived on Trellwan. It had become a refuge for him from Kai Griffith's demands and criticisms and from the crowded barracks. At times, it had even given refuge from the the gentle but critically sharp eye of his father. Once, several local years ago, he had brought Mara here for a few hours' gentle diversion. He'd hoped she would feel as enthralled with the cavern's beauty as he, and had been keenly dissappointed by her lack of response. The mouth of the Rift was too noisy, she'd told him, the air too wild and wet, the water-worn rock too cold and hard for what they'd planned to do.
He'd not returned for several local days after that episode, but not even Mara could long dim his enchantment with the place. Though Grayson returned many times after that day, he had always come alone.
The Rift was where he needed to be now. It had taken only a few moments to find a Sarghad militia ground effect skimmer parked at the fringe of the churning street mob. He felt little compunction about taking the machine. It was, after all, one of the light military vehicles the Commandos had given the local militia shortly after the garrison had arrived. It had been signed over to the locals as part of the mutual military training and assistance agreement between Trellwan and the Commonwealth government
After what Grayson had been through in the last few hours, he felt the Trells at least owed him some transportation. The skimmer carried him on a swirling trail of dust out of Sarghad and across the irrigated fields north of the city.
There was vegetation there, stubby and stained dark blue by Trellwan's copper sulfide-based analogue of chlorophyll. A single, wide, rust-crusted pipe brought water down from the mountains to the north, irrigating the patchwork of blue vegetation alternating with low, dull silver agrodomes that stretched into the desert beyond the city. Humans could not eat the local vegetation, and so grew fields of imported grains and vegetables inside the temperature and light-controlled shelter of the agrodomes. Local crops adapted to Trellwan's cyclical climate provided the spices (safe if ingested in small quantities) and the shrub-grown mineral-dense hardwoods that were the staples of Trellwan's offplanet trade.
Grayson guided the skimmer across the fields, opening up the little craft's considerable full speed, angling toward the glacier nesting in its V-shaped notch in the mountains to the north. There were a few people about, mostly field workers urging scaly-humped lannics out of low, domed shelters. Now that the attackers had gone, work in the fields and agrodomes would continue. None of the workers took notice of the hovercraft's flight
There were switchback paths up the face of the mountains, but eventually he had to leave the skimmer among a jumble of boulders. From there, he plunged into a network of low-ceilinged caverns that would lead him into the mountain's heart, and then into the vault of the main Rift.
Grayson was aware first of the sound of the Rift, a dull thunder audible across ten kilometers even in the streets of Sarghad. In the caverns, the booming roar rang and pounded through rock channels and drummed at his senses like something alive. The sound rang out only during the time between early Thirday and early Firstday when the icepacks were melting and pouring into the 200-meter-deep hollow of the Rift, but Grayson knew what to do. He used to bring along ear protectors, but then discovered that wads of slick, waxy yellow clay from the cavern floor would work as well to protect his hearing. He carefully plugged his ears, then made his way up the slanting cavern trail toward the source of the thundering roar.
There was a ledge, the remnant of some age-old convulsion of the planet's crust, which ran along the riftwall halfway up between the translucent glow of the ice ceiling and the shadowed dimness of the spray-shrouded lake below. On that ledge, he was surrounded by the mountain's exultant roar and intense vibration. The air was cool, heavy with moisture and alive with the thrumming waves of sound from the cataracts of water. The central void of the Rift was filled with water funnelling from channels and water-worn passages within the ice roof overhead. From time to time, multi-ton boulders of ice would break free and fall 200 meters through spray-filled space, and plunge into the foam and fury below.
Grayson made his way along the ledge to the left. There, to the south, the Rift opened up to air and light, and the ice ceiling gave way to clear sky framed by the surrounding cliffs. Through the opening, he could see the helicopter pad on the roof of the Castle five kilometers out and down. Beyond and below that was the wheel-shaped sprawl of Sarghad. At his feet, the Rift wall dropped straight down 100 meters to the edge of the lake.