Friday, August 6, 2010

NORTH POLAR LAYERS OF MARS



The north polar layered deposits are layers of dusty ice up to 2 miles thick and approximately 620 miles in diameter. We can see the layers exposed on the walls of troughs and scarps cut into the deposits, such as the trough wall imaged here.

The bright region at the top is the flat surface above the trough wall; it is higher than the terrain underneath. The wall exposing these layers has a vertical relief of about 1970 feet.

It is thought that the north polar layered deposits likely formed recently (i.e., millions of years ago) as rhythmic variations in Mars' orbit changed the distribution of water ice around the planet. As ice moved to and from the polar region in response to a changing climate, layers of ice and dust built up at the poles. By studying the history of these deposits, we hope to understand how the Martian climate has changed, similar to how scientists on Earth study ice cores from the North and South Poles.

Three things are immediately apparent about the layers exposed on this trough face. First, individual layers have different surface textures, which some scientists believe could reflect changing physical properties (such as dust content or ice grain size) of the underlying layer. Second, there are several unconformities, or places where one layer is interrupted and overlain by another layer. These unconformities are due to periods where layers were eroded or removed, followed by times when new layers were deposited. Mapping the locations of unconformities can tell us how the deposit shrank and grew over time, and tell us where large changes in climate occurred, causing water ice to be removed from the polar regions. Finally, the dark and bright streaks are due to recent winds blowing surface frost around, and can tell us about wind patterns in the current polar climate.

This was imaged by the HiRISE camera onboard the Mars Reconnaissance Orbiter. HiRISE is the most powerful camera of its kind ever sent to another planet. Its high resolution allows us to see Mars like never before and could help other missions choose a safe spot to land for future exploration.

Credit: NASA/JPL/University of Arizona

GREAT BALL OF FIRE


On August 1, 2010, almost the entire Earth-facing side of the sun erupted in a tumult of activity. This image from the Solar Dynamics Observatory of the news-making solar event on August 1 shows the C3-class solar flare (white area on upper left), a solar tsunami (wave-like structure, upper right), multiple filaments of magnetism lifting off the stellar surface, large-scale shaking of the solar corona, radio bursts, a coronal mass ejection and more.

This multi-wavelength extreme ultraviolet snapshot from the Solar Dynamics Observatory shows the sun's northern hemisphere in mid-eruption. Different colors in the image represent different gas temperatures. Earth's magnetic field is still reverberating from the solar flare impact on August 3, 2010, which sparked aurorae as far south as Wisconsin and Iowa in the United States. Analysts believe a second solar flare is following behind the first flare and could re-energize the fading geomagnetic storm and spark a new round of Northern Lights.

Credit: NASA/SDO/AIA