郊狼谷的棉白杨和红砂岩，格兰峡谷国家保护区，犹他州 Cottonwood trees and red sandstone in Coyote Gulch, Glen Canyon National Recreation Area, Utah (© Stephen Matera/Tandem Stills + Motion)

郊狼谷的棉白杨和红砂岩，格兰峡谷国家保护区，犹他州 Cottonwood trees and red sandstone in Coyote Gulch, Glen Canyon National Recreation Area, Utah (© Stephen Matera/Tandem Stills + Motion)

沐浴在秋天的色彩中 Awash in autumn hues

秋分

秋天正式开始了！在北半球，今年的9月23日是秋分，这一天标志着秋天开始，太阳直射地球赤道，白昼和黑夜相等。在南半球，同样如此，但南北半球的季节是相反的，北半球秋分，南半球则是春分，正在迎接春天的到来。

在今天的图片中，这棵隐身于秋色中的棉白杨可能正在红砂岩中玩“躲猫猫”。郊狼谷位于犹他州南部的格兰峡谷国家保护区，由于水和其他液体的氧化作用，以及含铁矿物质的存在，峡谷呈现出红橙色。

Autumnal equinox

Autumn has officially begun! In the Northern Hemisphere, the autumnal equinox falls on September 23 this year, marking the beginning of autumn. Today is one of the two moments in the year when day and night are equal in length, thanks to the sun's location exactly above the equator. In the Southern Hemisphere, today marks the vernal equinox and they are heading into spring.

Camouflaged in autumn colors, the cottonwood tree in today's image might be playing peek-a-boo among the red sandstones of Coyote Gulch in southern Utah. Here in the Glen Canyon National Recreation Area, the canyon is painted orange by oxidizing water and other fluids, as well as iron-filled minerals.