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STS-120 day 2 highlights

Flight Day 2 of Discovery's mission focused on heat shield inspections. This movie shows the day's highlights.

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STS-120 day 1 highlights

The highlights from shuttle Discovery's launch day are packaged into this movie.

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STS-118: Highlights

The STS-118 crew, including Barbara Morgan, narrates its mission highlights film and answers questions in this post-flight presentation.

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 Mission film

STS-120: Rollout to pad

Space shuttle Discovery rolls out of the Vehicle Assembly Building and travels to launch pad 39A for its STS-120 mission.

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Dawn leaves Earth

NASA's Dawn space probe launches aboard a Delta 2-Heavy rocket from Cape Canaveral to explore two worlds in the asteroid belt.

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Dawn: Launch preview

These briefings preview the launch and science objectives of NASA's Dawn asteroid orbiter.

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Martian avalanches caught on film by orbiting probe
BY EMILY BALDWIN
ASTRONOMY NOW

Posted: March 4, 2008


A cloud of dust rises in the wake of a Martian avalanche in this images from the Mars Reconnaissance Orbiter. Image: NASA/JPL-Caltech/University of Arizona

Cameras orbiting Mars as part of NASA's High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter have captured four avalanches in action.

Material, likely including fine-grained ice and dust, has detached from a 700-metre high cliff and cascaded to gentler slopes below. The clouds of fine material that have risen into the air have been captured by the HiRISE cameras. In just one HiRISE image, at least four avalanches in the northern polar regions, where it is now spring, have been observed. In the main image the path of the falling material can be seen, possibly originating from just below the carbon dioxide frost encrusted surface and tumbling the 700 metres to the shallower slopes below. The billowing debris cloud is around 180 metres across and extends out 190 metres from the base of the cliff. Shadows towards the lower left of each cloud show that these features are three-dimensional and are hanging above the ground and in front of the cliff face, and are not markings on the ground.

The trigger mechanism for the avalanches is not confirmed, but it is likely that the disappearance of the carbon dioxide frost and the expansion and contraction of ice in response to temperature changes may be the cause. Other possibilities include a nearby Mars-quake or meteorite impact, or perhaps vibrations caused by a different debris fall in the area.


Another view from the Mars Reconnaissance Orbiter of a Martian Avalanche. Image: NASA/JPL-Caltech/University of Arizona

Most of the images taken by Mars orbiting cameras record few changes to the surface, revealing landscapes millions of years old. With the exception of a few seasonal changes and the occasional dust devil, it is extremely unlikely that such a dynamic event as an avalanche is captured by still photography. Events like these are useful in trying to unlock the secrets of active processes that occur on other planets.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.
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Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.
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3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!
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