NASA image of the day (imatge del dia, NASA)

This image shows the west-facing side of an impact crater in the mid-latitudes of Mars' northern hemisphere. Like many mid-latitude Martian craters, this one has gullies along its walls that are composed of alcoves, channels and debris aprons. The origins of these gullies have been the subject of much debate; they could have been formed by flowing water, liquid carbon dioxide or dry granular flows. Many of the other features observed in and around this crater are indicative of an ice-rich terrain, which may lend credence to the water formation hypothesis for these gullies. The most notable of these features is scalloped terrain in and around the crater. This type of terrain has been interpreted as a sign of surface caving, perhaps due to sublimation of underlying ice. Sublimation is the process of a solid changing directly to a gas. Another sign of ice is the presence of parallel lines and pitted material on the crater floor. Parallel linear cracks are also observed along the crater wall over the gullies, which could be due to thermal contraction of ice-rich material. together, these features are evidence for ice-rich material having been deposited in this region during different climatic conditions, material that has subsequently begun to melt and/or sublimate under current conditions. More recently, wind-blown deposits have accumulated around the crater, as evidenced by the parallel ridges dominating the landscape. The High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter took the image on April 13, 2010. Image Credit: NASA/JPL-Caltech/University of Arizona

In this image, engineers test the RL-10 engine in NASA Lewis (now Glenn) Research Center's Propulsion Systems Laboratory. Developed by Pratt & Whitney, the engine was designed to power the Centaur second-stage rocket. Centaur was responsible for sending the Surveyor spacecraft on its mission to land on the moon and to explore the surface in the early stages of the Apollo Program. Image Credit: NASA

Thilo Kranz, a staff member at DLR, the German Space Agency, took this image of the transit of the International Space Station ISS with Space Shuttle Atlantis during the STS-132 mission. Kranz photographed "the ISS as it passed across the solar disk in just 0.51 seconds ... At this time, preparations for undocking of space shuttle Atlantis during its final mission, STS-132, were ongoing. You can see the still docked shuttle in the 11 o'clock position. Also, you may recognise the solar panels and the large radiators. In the full resolution version of this image, you can also see the Soyuz capsule. Close to the centre of the sun, a group of sunspots is visible." Visit the DLR News Blog for more information. Image Credit: Thilo Kranz/DLR

Space shuttle Atlantis' main gear touched down on Runway 33 at the Shuttle Landing Facility at NASA's Kennedy Space Center in Florida at 8:48 a.m. EDT, completing a 12-day mission to the International Space Station. On board were Commander Ken Ham, pilot Tony Antonelli, Garrett Reisman, Michael Good, Steve Bowen and Piers Sellers. The six-member STS-132 crew carried the Russian-built Mini Research Module-1 to the International Space Station. STS-132 is the last planned flight for Atlantis. Image Credit: NASA/Carl Winebarger

Spacewalker Michael Good, barely visible in his white spacesuit against the station, participated in the STS-132 mission's third and final spacewalk. During the six-hour, 46-minute spacewalk, Good and fellow NASA astronaut Garrett Reisman completed the installation of the final two new batteries for the B side of the port 6 solar array. Image Credit: NASA

Astronauts Michael Good (left) and Garrett Reisman look through the aft flight deck windows of space shuttle Atlantis during the mission’s third aspacewalk. During the spacewalk, Good and Reisman completed the installation of the final two of the six new batteries for the B side of the port 6 solar array. In addition, the astronauts installed a backup ammonia jumper cable between the port 4 and 5 trusses of the station and transferred a power and data grapple fixture from the shuttle to the station. Image Credit: NASA

Earth's horizon and the blackness of space provide the backdrop for Atlantis' aft section while it was docked with the International Space Station during the STS-132 mission. Image Credit: NASA

Anchored to a Canadarm2 mobile foot restraint Garrett Reisman conducts the mission's first spacewalk. During the seven-hour, 25-minute spacewalk, Reisman and Steve Bowen installed a second antenna for high-speed Ku-band transmissions and added a spare parts platform to Dextre, a two-armed extension for the station’s robotic arm. Image Credit: NASA

This image features the Atlantis' cabin and forward cargo bay and a section of the International Space Station while the two spacecraft remain docked, photographed during the STS-132 mission's first spacewalk. Image Credit: NASA

Anchored to the Canadarm2 mobile foot restraint, Garrett Reisman performed construction and maintenance activities outside the station during the STS-132 mission's first spacewalk. During the seven-hour, 25-minute spacewalk, Reisman and NASA astronaut Steve Bowen installed a second antenna for high-speed Ku-band transmissions and added a spare parts platform to Dextre, a two-armed extension for the station’s robotic arm. Image Credit: NASA

NASA astronaut Garrett Reisman takes a self-portrait visor while participating in the first of three spacewalks scheduled for the Atlantis crew and their Expedition 23 hosts. Though three spacewalks will involve only three astronauts (two on each occasion) who actually leave the shirt-sleave environments of the two docked spacecraft, all twelve astronauts and cosmonauts have roles in supporting the work. Part of the space station and the blue and white Earth are among the objects seen in his visor. Fellow spacewalker Steve Bowen, mission specialist, is out of frame. Image Credit: NASA

The Expedition 23 crew snapped this imageof the underside of Atlantis' crew cabin, during a survey of the approaching space shuttle prior to docking with the International Space Station. Image Credit: NASA

Space shuttle Atlantis soars to orbit from Launch Pad 39A at NASA's Kennedy Space Center in Florida on the STS-132 mission to the International Space Station at 2:20 p.m. EDT on May 14. The third of five shuttle missions planned for 2010, this was the last planned launch for Atlantis. Image Credit: NASA/Kenny Allen

Space shuttle Atlantis lifted off from Launch Pad 39A at NASA's Kennedy Space Center in Florida on the STS-132 mission to the International Space Station at 2:20 p.m. EDT on May 14. The third of five shuttle missions planned for 2010, this was the last planned launch for Atlantis. The Russian-built Mini Research Module-1, also known as Rassvet, or "dawn," will be delivered and it will provide additional storage space and a new docking port for Russian Soyuz and Progress spacecraft. The laboratory will be attached to the bottom port of the station's Zarya module. The mission's three spacewalks will focus on storing spare components outside the station, including six batteries, a communications antenna and parts for the Canadian Dextre robotic arm. Image Credit: NASA

A family of Osprey are seen outside the NASA Kennedy Space Center Vehicle Assembly Building in Cape Canaveral, Fla. on Thursday, May 13, 2010. The Merritt Island National Wildlife Refuge overlaps Kennedy and provides a habitat for 330 species of birds, including the osprey. A variety of other wildlife--117 kinds of fish, 65 types of amphibians and reptiles, 31 different mammals, and 1,045 species of plants--also inhabit the refuge. The countdown is on for today's scheduled launch of space shuttle Atlantis on its STS-132 mission. At NASA's Kennedy Space Center in Florida, technicians at Launch Pad 39A continue preparations for the liftoff at 2:20 p.m. EDT. Image Credit: NASA/Bill Ingalls

A heavy runaway star is rushing away from a nearby stellar nursery at more than 250,000 miles an hour, a speed at which one could travel to the our moon and back in two hours. This is the most extreme case of a very massive star that has been kicked out of its home by a group of even heftier siblings. The homeless star is on the outskirts of the 30 Doradus Nebula, a raucous stellar breeding ground in the nearby Large Magellanic Cloud. The stellar nusery is seen at the center of this image. The finding bolsters evidence that the most massive stars in the local universe reside in 30 Doradus, making it a unique laboratory for studying heavyweight stars. Also called the Tarantula Nebula, 30 Doradus is roughly 170,000 light-years from Earth. Tantalizing clues from three observatories, including the Hubble Space Telescope's newly installed Cosmic Origins Spectrograph (COS), and some old- fashioned detective work, suggest that the star may have traveled about 375 light-years from its suspected home, a giant star cluster called R136. Nestled in the core of 30 Doradus, R136 contains several stars topping 100 solar masses each. Visit Hubble Catches Heavyweight Runaway Star for more information. Image Credit: NASA, ESA, C. Evans (Royal Observatory Edinburgh), N. Walbom (STScI), and ESO