STS036-151-16 Southwest Libya March 1990 The desert scene in this photograph is located just west of one of the few strategic north-south trade routes through southwest Libya. The extensive oasis of Ubari (northeast part of the photograph) is located just north of the darker, eroded, rocky desert. The desert extends in a general northeast-southwest direction for approximately 45 miles (75 kilometers), from the discernible northern escarpment to the northern edge of the sandy Marzuq Desert. A well-entrenched drainage pattern indicates flows toward the south and southeast. The darker rock outcrops are slightly tilted sedimentary rocks sandwiched between the sandy Ubari and Marzuq Deserts. The vivid, dark green, circular features are center-pivot irrigated fields---usually 0.5 mile (0.8 kilometer) in diameter---where sufficient well water is available to practice farming.