Zunil (crater)

MarsGeo-Crater
name=Zunil


discoverer = McEwen et alcite conference|author=McEwan et al|title=Discovery of a large rayed crater on Mars: Implications for recent volcanic and fluvial activity and the origin of Martian meteorites|conference=Lunar and Planetary Science Conference|date=2003|url=http://www.lpi.usra.edu/meetings/lpsc2003/pdf/2040.pdf]
region = Athabasca Valles
diameter = 10.4 km
latitude = 7.8
N_or_S = N
longitude = 193.9
E_or_W = W
eponym = Zunil

Zunil is an impact crater in Athabasca Valles, Mars with a diameter of convert|10.4|km|abbr=on|1. It is named after the Guatemalan town of the same name. The crater was discovered by McEwan et al after following bright streaks of material along the crater's radial lines back to the crater. Prior to the discovery, large craters with ray systems had not been seen on Mars.

The debris from a recent landslide was spotted on the south-east wall of the crater by HiRISE in December 2006. [cite web|url=http://hirise.lpl.arizona.edu/PSP_001764_1880|title=Recent Landslide in Zunil Crater (PSP_001764_1880)|publisher=University of Arizona|accessdate=2008-06-28]

Formation

The impact which formed Zunil occurred no more than a few million years ago and hence the crater is in a relatively pristine form. It was probably not produced in a high velocity impact, such as from a comet. The crater formed in basalt deposited 165 - 177 million years ago.

The impact created a ray system, visible in the infrared, that extends up to 1600 km from the crater and produced hundreds of millions of secondary craters with diameters ranging from 10 m to 100 m. Very few of these secondary craters lie within 80 km of Zunil. Around 80% of the craters in Athabasca Valles are Zunil secondaries. If similar impacts also produced comparable amounts of secondaries, this calls into question the accuracy of crater counting as a dating technique for geologically young Martian surface features. cite journal|title=Who can Read the Martian Clock?|journal=Science|author=Kerr, R|volume=312|date=2006|pages=1132 - 1133|doi=10.1126/science.312.5777.1132] cite journal|author=McEwan, A.S. et al|url=http://www.mars.asu.edu/christensen/classdocs/mcewen_zunil_Icarus_2005.pdf|title=The rayed crater Zunil and interpretations of small impact craters on Mars|journal=Icarus|volume=176|pages=351 - 381|date=2005|accessdate=2006-09-08]

A simulation of the Zunil impact ejected on the order of ten billion rock fragments greater than 10 centimeters in diameter, the total ejecta comprising 30 km³. These formed about a billion secondary craters 10 m in size up to 3500 km away from the primary impact. It is possible that some of these fragments from the impact made it to Earth to become shergottites, a form of Martian meteorite.

References

ee also

*List of craters with ray systems

External links

* [http://themis.asu.edu/discoveries-zunil Themis page about Zunil crater]
* [http://www.psrd.hawaii.edu/Jan07/MarsRayedCraters.html Rayed craters on Mars]