Ancient desert markings imaged from orbit   This image of the Nasca plain in southern Peru was acquired by the Compact High Resolution Imaging Spectrometer (CHRIS) instrument aboard ESA's Proba spacecraft on 26 September 2003. It shows desert roads as well as faint traces of the largest of the ancient Nasca Lines etched by Peruvian indians on the arid landscape. Water channels caused by flash flooding are also visible.   The Panamerican Highway cuts straight through the mysterious figures and geometric shapes of the Nasca Lines near Nasca in southern Peru. The highway was built in 1937, before that section of the Lines had been discovered. The Lines are too large to be appreciated from the ground, but rather can only be seen from the air, although they were drawn in the sand before 700A.D. by the Nasca Indians, long before airplanes and hot-air balloons existed.   Proba-1, Project for On Board Autonomy, demonstrates the potential and feasibility of small satellites for advanced scientific and Earth Observation missions.   An interferometric coherence image derived from two scenes acquired by the ERS-2 satellite, first in 1997 and then in 1999. The bright regions in the image show where the two scenes are highly correlated, indicating that there has been very little change in the terrain surface during the 2 year interval between the acquisitions. The darker regions show where de-correlation has occurred over this period, highlighting possible problem areas where erosion may be taking place. The Nasca pampa is the bright region of high coherence in the centre-right of the image flanked by the highly de-correlated river valleys. The dark linear features are roads and tracks. The areas of run-off are clearly visible cutting across the pampa from the Andean foothills on the right, as was also evidenced by the Proba image.   This aerial photograph shows examples of the Nasca lines. The drainage channels right of centre are indicative of erosion caused by run-off water from the Andes. Recent evidence suggests that some of the lines and figures are now at risk from increased water erosion and deposits left by from flash floods and run-off from the adjacent Andean foothills, a consequence, it is thought, of the El Niño phenomenon in the Pacific Ocean.   Team member Nicholas Walker surveys the Nasca Lines from the ground. Radar images acquired by ESA spacecraft are being used to assess whether they are in danger of being eroded by both human activities and natural flooding. Release date: 22 June 2004