vendredi 10 février 2017

Nine Kilometer Impact Crater & Unlocking an Impact Crater's Clues












NASA - Mars Reconnaissance Orbiter (MRO) patch.

Feb. 10, 2017

 Nine Kilometer Impact Crater

This image reveals an impact crater, nine kilometers in diameter, with a central peak. Impact craters of various sizes and ages can be found across the Martian surface. Each impact crater on Mars possesses a unique origin and composition, which makes the HiRISE team very interested in sampling as many of them as possible!

Like the impact of a droplet into fluid, once an impact has occurred on the surface of Mars, an ejecta curtain forms immediately after, contributing to the raised rim visible at the top of the crater's walls. After the formation of the initial crater, if it is large enough, then a central peak appears as the surface rebounds. These central peaks can expose rocks that were previously deeply buried beneath the Martian surface.

The blue and red colors in this enhanced-contrast image reflect the effects of post-impact sedimentation and weathering over time.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.

Impact Crater & Unlocking an Impact Crater's Clues

Mars is a dynamic planet. HiRISE has witnessed many surface changes over the past ten years, including hundreds of new craters formed by ongoing impacts. Most of these impacts are likely caused by asteroids that have strayed into collision courses with Mars. The planet's much thinner atmosphere compared to Earth makes small asteroids less likely to burn up prior to hitting the Martian surface.

This new crater, which formed explosively at the point of impact, has a diameter of roughly 8 meters (about 25 feet), but its surrounding blast zone and ejecta extend over a kilometer (about one mile) beyond the crater itself. The materials exposed nearest the crater have distinctive yellowish and lighter grey appearances, while more distant ejected materials range from dark brown to bright bluish in an enhanced-color view. These varied materials may have originated from different layers penetrated by the impact.

This new impact was discovered using the lower-resolution Context Camera (CTX), also on board Mars Reconnaissance Orbiter. An older CTX image of this region from May 2012 shows a uniformly dust-covered surface, while a newer CTX image from September 2016 reveals the crater's dark blast zone. New craters on Mars are easiest to locate in such dust-coated terrains, where they provide opportunistic "road cuts" that allow scientists to see beneath the dust blanket and determine the underlying rock compositions and textures.

Artist's view of Mars Reconnaissance Orbiter (MRO). Image Credits: NASA/JPL-Caltech

This particular crater formed about 300 kilometers (roughly 200 miles) east of the Spirit rover's final resting spot in Gusev Crater.

Original image scale range: 26.2 cm/pixel (with 1 x 1 binning) so objects ~79 cm across are resolved. Map projected scale: 25 cm/pixel and North is up.

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.

Mars Reconnaissance Orbiter (MRO): http://www.nasa.gov/mission_pages/MRO/main/index.html

Images (mentioned), Text, Credits: NASA/JPL-Caltech/Univ. of Arizona/Tony Greicius.

Greetings, Orbiter.ch

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