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Gallery: Fleet-Footed Flyby Reveals Mercury?s Unseen Surface

: Photo: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of WashingtonWASHINGTON, D.C. -- The first mission sent to orbit Mercury flew by the planet closest to the sun for the second time earlier this month, capturing images of most of its previously unseen surface. On Oct. 6, NASA's MErcury Surface, Space ENvironment, GEochemistry and Ranging spacecraft, or Messenger, passed just 125 miles above Mercury and took more than 1,200 pictures of its heavily cratered surface. During the second of three scheduled flybys, the probe used Mercury's gravity to alter its path, which will help it eventually settle into orbit around the planet in 2011. A briefing about the early scientific findings from the mission will be shown live in a NASA Television webcast Oct. 29 at 1 p.m. EDT. Left: During its approach to the solar system's innermost planet, NASA's Messenger probe took this image of a crescent Mercury. The spacecraft was still an hour and a half from its closest encounter when it imaged this terrain, which hadn't been seen on Messenger's first flyby or by the Mariner 10 spacecraft, which flew by Mercury in 1974 and 1975. The image is one of a set of 11 taken through different filters to study the colors of the surface.: Photo: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of WashingtonThis image, taken as Messenger flew away from its closest approach to Mercury, was one of the first to be sent back to Earth. The bright spot near the center of the image is Kuiper crater. Most of the terrain to the east of Kuiper had never been seen before. A striking characteristic of this newly imaged area is the large pattern of rays that extend from a relatively young crater in the northern region of Mercury to south of Kuiper. : Photo: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of WashingtonJust an hour before Messenger reached its closest approach to Mercury, the probe took this close-up picture of a heavily cratered terrain in an area that had never before been imaged. The features in the foreground, near the right side of the image, are close to the line between the sunlit day side and dark night side of the planet, so shadows are long and prominent and make the topography stand out.: Photo: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of WashingtonThe sun's slanting rays illuminate Machaut crater in this image. The crater, named for the medieval French poet and composer Guillaume de Machaut, is about 60 miles across. The floor of the crater has been coated with lava, which has in turn been peppered with more small craters. : Photo: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of WashingtonThis shot was taken just minutes after Messenger passed its closest point to the surface of Mercury, while the spacecraft was moving at 3.8 miles per second. It is the highest resolution color image ever taken of the planet. The largest crater, near the top of the photo, is called Polygnotus and is 83 miles in diameter.

Robert Dalrymple: Get Ready for Extreme Weather

Katrina was just the beginning. The long, hot summer that is global warming will be characterized by rising water levels, unprecedented coastal erosion, and more Category 5 hurricanes. Robert Dalrymple, a coastal engineer at Johns Hopkins University, warns that the nation is woefully unprepared. They said Katrina was a 100-year storm but then, so was Rita a month later, he says. What does that tell you? Dalrymple offers the next president a three-point plan to prepare for the coming era of marine mayhem. How to Avert Disaster 1. Plan the Evacuation If another huge storm strikes tomorrow, we need to know how to beat a timely retreat. Emergency officials say we must be able to empty vulnerable cities like Miami, New Orleans, and Charleston in 24 hours. Most probably couldn't come anywhere close to that goal as recent history demonstrates. The main bottleneck, Dalrymple says, is transportation. Remember the evacuation of Houston during Hurricane Rita? Cars were stuck for miles along the freeway. What's needed, he says, is a reverse-laning system that could be implemented at the push of a button, converting all lanes of traffic into a one-way super-highway out of town. 2. Restore the Wetlands Coastal marshes and swamps provide a natural buffer against ocean storms, absorbing floodwaters like giant sponges. Given that Louisiana has lost more than 1,900 square miles of coastal wetland in the past century, the devastation of New Orleans by Katrina in 2005 was all but inevitable. Because the Mississippi has been so extensively dredged and channelized, it shoots all the sediment needed to sustain these areas right out into the Gulf, Dalrymple says. Current efforts to fortify the city's levees won't be enough. His solution: Reroute the river to aim the waterborne soil where it's needed. That wouldn't be cheap, but the alternative is even less palatable. How to Avert Disaster Click for full-size image. 3. Save the Beaches Beaches are another crucial storm buffer. But those sandy strands are disappearing, putting heavily populated regions like the mid-Atlantic at risk. The erosion is particularly severe around jetties and inlets, which alter shore currents. Seawalls built to fend off the encroaching waters only make things worse. The quickest and often the only practical solution, Dalrymple says, is to just pick up the sand from where it collects and haul it back to where it came from. An operation at the Indian River Inlet in Delaware is using a massive portable eductor (a dredging pump) to suck up offshore sand deposits. Dalrymple says we need to build more such units and put them to work soon. Robert Dalrymple is Professor of Civil Engineering at Johns Hopkins University.