Cover

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Half Title, Title Page, Copyright

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Contents

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pp. v-viii

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Introduction

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pp. ix-xii

The Mars Reconnaissance Orbiter (MRO) launched from Florida on August 12, 2005, carrying the High Resolution Imaging Science Experiment (HiRISE), the most powerful camera ever sent to another planet (by Earthlings). Our team was first selected to build HiRISE in November 2001, less than four years before launch. That was a very fast schedule for such a complex instrument! ...

Map of Mars

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p. xiii

Part I. Modern Mars

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pp. 1-2

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1. Dunes, Sand Sheets, and Wind

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pp. 3-32

We begin our armchair exploration by looking at some of the youngest landforms on Mars: sand dunes. Wind has eroded the surface of Mars over millennia, and sand dunes or other signs of wind are visible in almost every image that HiRISE has taken, in every type of terrain. Many of these dunes are in motion, migrating across the surface. Most have forms similar to dunes on Earth, ...

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2. Young Impact Craters

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pp. 33-52

Over the billions of years since the formation of the Solar System, planets have been pummeled by debris. These impacts continue today. Generally, an impactor leaves a crater on the surface of the body it hit. Ejecta is thrown radially outward, and large pieces may themselves cause secondary craters. The type of terrain hit by an impactor and its angle of impact will influence the properties of the crater. ...

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3. Gullies and Flows on Steep Slopes

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pp. 53-92

Gullies—or “ravines,” given their large scale in comparison to the features on Earth called “gullies”—are relatively common on steep slopes of terrain in certain areas of Mars. Material from a scalloped alcove at the top of the steep terrain moves through an incised narrow channel and is deposited in a fan-shaped apron as the slope becomes gentler. ...

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4. Landslides and Avalanches

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pp. 93-114

Landslides and avalanches are mass movements of material that occur on a variety of scales, from thin dust avalanches to giant landslides in Valles Marineris. ...

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5. Icy Middle Latitudes

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pp. 115-134

Between the equatorial region and the high latitudes of the polar region lies a vast portion of Mars referred to as the “icy mid-latitudes.” In this region, water ice could have been stable on the surface millions of years ago when the obliquity of Mars (the tilt of Mars’ rotational axis) was very different. Currently the obliquity of Mars is similar to Earth, but in the past it was much higher, ...

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6. Polar Ice Caps

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pp. 135-164

Both poles of Mars are covered by permanent polar caps. In the Northern hemisphere the top layer of the permanent polar cap is water ice, while in the Southern hemisphere, the top layer is carbon dioxide ice (dry ice). In both hemispheres, stacks of layers make up the permanent cap. The layers have varying amounts of both types of ice mixed with varying amounts of dust and sand, ...

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7. Seasonal Dry Ice

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pp. 165-186

Winter on Mars brings a layer of carbon dioxide ice (dry ice) up to a meter deep, frozen from the atmosphere or falling as snow onto the polar surface. In some locations the ice forms a translucent slab. In the spring, the dry ice sublimates (goes directly from a solid to gaseous state) with many exotic processes unlike anything on Earth. The ice layer may sublimate from the bottom, ...

Part II. Ancient Mars

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pp. 187-188

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8. Channels and Alluvial Fans

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pp. 189-210

There were multiple times long ago in Martian history that water flowed on the surface. Today Mars’ climate is too cold and the pressure of the atmosphere is too low for liquid water to be stable, except in rare times and places or if the water is sufficiently salty (i.e., the recurring slope lineae). But we see evidence for a very different climate in the geologic record— ...

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9. Sedimentary Layers and Lakes

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pp. 211-246

Ancient lakes may have provided environments in which life once flourished on Mars, so they are of great interest. The water is long gone, but lakes leave behind finely layered sediments that were deposited in the water. These sediments may have rapidly buried signs of life, preserving their signatures. HiRISE provides the spatial resolution needed to see the fine layering and provide further clues, ...

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10. Mineral Diversity

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pp. 247-270

The history of Mars’ climate is preserved in the mineralogy of its rocks. In the earliest era, over four billion years ago, clays were formed by aqueous alteration of volcanic rock. We see these clays (carbonates and phyllosilicates) in ancient terrains. After that period, intense volcanic activity distributed pyroxenes and olivine and changed the environment from alkaline to acidic. ...

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11. Volcanism

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pp. 271-296

Volcanic eruptions on Mars have molded its surface at scales from large to small. The largest volcanic complex, which includes Olympus Mons and Tharsis Montes, influenced the global shape of Mars billions of years ago. At regional scales, volcanic flows are as young as a few millions of years. It would take thousands of HiRISE images to cover the largest volcanoes, ...

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12. Tectonics

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pp. 297-312

Tectonics refers to the structural deformation of the outer layers of a planet, including giant extensional rifts such as Valles Marineris and compressional landforms called “wrinkle ridges.” Tectonics includes updoming, subsidence, warping, buckling, and fracturing, producing some of the most interesting landforms on the Red Planet. ...

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13. Floors of Large, Ancient Impact Craters

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pp. 313-332

There are many large, ancient impact craters on Mars that are too large to be captured in a single HiRISE image. We can, however, cover many of the central peaks, which often contain megabreccia (mix of angular rocks with pieces larger than one meter in diameter). ...

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14. Bedrock Geology

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pp. 333-362

We’ve already seen many images of bedrock in different settings (sedimentary layers, ancient craters, and locations with mineral diversity). Here, we show additional examples of bedrock exposures. ...

Part III. All Over the World

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pp. 363-364

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15. Diverse Landscapes

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pp. 365-386

Previous chapters have focused on particular types of surface features, but Mars contains complex landscapes with infinite variety. Here, we show some examples of such landscapes. ...

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16. Mysteries and Oddities

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pp. 387-406

We’ve learned a great deal about Mars from HiRISE, but the origins of some landforms remain mysterious or have explanations that may seem odd. We love mysteries and oddities. ...

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17. Rovers and Landers

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pp. 407-426

Mars is an unforgiving place, where more missions have failed than succeeded. But the ones that do touch down and set their fragile machine bodies onto this alien world are a spectacular achievement of engineering, planning, and vision. We are living witnesses to the ingenuity of our species to peer up close at the surface of another planet. ...

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The Sons of Ares

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pp. 427-432

We acquired this dramatic view of the Martian moon Phobos on March 23, 2008. The most prominent feature is the large impact crater called Stickney (right). With a diameter of nine kilometers, Stickney Crater is the largest feature on Phobos and has a series of grooves and crater chains. ...

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Acknowledgments

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pp. 433-434

We thank everyone who has supported HiRISE since 2001, including the MRO teams at the Jet Propulsion Laboratory in California, Lockheed Martin and Ball Aerospace in Colorado, NASA, the University of Arizona, the science community, and the general public from around the world. ...

Glossary

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p. 435

About the Authors

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