The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter recorded this image of the Palos Crater on equatorial Mars on March 8, 2010. The target for the photo was a suggestion submitted through the camera team's HiWish public-suggestion program. NASA/JPL-Caltech/University of Arizona
The Martian north polar layered deposits are an ice sheet much like the Greenland ice sheet on Earth. Just as with the ice sheet in Greenland, this Martian ice sheet contains many layers that record variations in the planet's climate. Sometimes icy layers can be ablated away during warm climates. Later the ice sheet can be buried by new ice layers and grow in size again. It's likely that many of these cycles have occurred over the ice sheet's history. NASA/JPL-Caltech/University of Arizona
This image covers the northern edge of the solar system's largest volcano, Olympus Mons. The margin of Olympus Mons is defined by a massive cliff several miles tall. At this location, it is nearly 23,000 feet tall. The cliff exposes the guts of the volcano, revealing interbedded hard and soft layers. The hard layers are lava and the soft layers may be dust (from large dust storms) or volcanic ash. NASA/JPL-Caltech/University of Arizona
Samara Valles is one of the longest ancient valley systems on Mars. This system traverses more than 620 miles toward the northwest across the heavily cratered southern highlands eroding into the gentle slopes of Terra Meridiani. The valley terminates in the northern lowlands within the Chryse basin where both Viking Lander 1 and Pathfinder are located.
NASA/JPL-Caltech/University of Arizona
The terrain in this image lies in the Deuteronilus Mensae region along the highland-lowland dichotomy boundary in the northern hemisphere of Mars. This region contains many mesas surrounded by lobate debris aprons that are thought to be ice-rich. These aprons have been interpreted as a variety of possible features including rock glaciers, ice-rich mass movements, or debris-covered glacial flows. Recent radar data from the Shallow Radar instrument on the Mars Reconnaissance Orbiter has shown them to be composed of nearly pure ice. NASA/JPL-Caltech/University of Arizona
This image reveals yard-scale surface textures of mesas and knobs in the Aureum Chaos region of Mars. Most of the rocks in this area appear to have formed originally as laterally continuous layers through volcanic or sedimentary processes. Loss of groundwater or ice could have then caused the ground to collapse, forming the current surface features of deep valleys and isolated hills with sloped faces. NASA/JPL-Caltech/University of Arizona
Common to the northern plains of Mars are boulder-strewn landscapes otherwise devoid of major features except a few impact craters. This image in the Cydnus Rupes region of northern Utopia Planitia is an excellent example of this sort of terrain. It was taken by the HiRISE camera on Feb. 20, 2010. NASA/JPL-Caltech/University of Arizona
This image covers some high-standing topography just outside the rim of an impact crater about 19 miles in diameter near a Martian hill named Zephyria Tholus. What formed this hill? Could it be a volcano? That was hypothesized in a paper published in 2001, and this suggestion was entered to test that idea, perhaps from seeing internal layering exposed by the crater. Mostly this image shows a dust mantle, hiding the bedrock it was intended to study. NASA/JPL-Caltech/University of Arizona
Dimitri Bontinck, a Belgian ex-soldier who retrieved his own son from the Islamic State, goes back to the Turkish-Syrian border to help another anguished father. But luring away jihadis is hard work.
ByDominique Soguel, Correspondent
Europe’s anguish over the rise of homegrown jihadis – young Muslims and Muslim converts who flock to the banner of foreign extremist groups, especially the Islamic State – was on private display here this past week.