Meteors and meteorite falls in Morocco

During the last eighty years, thirteen meteorite falls were recorded in Morocco, which ten are well documented and named Douar Mghila, Oued el Hadjar, Itqiy, Zag, Bensour, Oum Dreyga, Benguerir, Tamdakht, Tissint and Aoussred. It represent only 0.011 % of the Moroccan declared meteorites.The authenticated observed falls represent three types of different meteorites, eight ordinary chondrites (Four of type LL, three of type H and one of type EH), one carbonaceous chondrite and one Shergottite basaltic achondrites. The Morocco meteorite fall recovery rate, during the past eighty years, is low 0.11 falls per year on average per 2.11 km 2 (or approximately one fall recovery per 10 year time interval).


INTRODUCTION
As samples from minor planets, meteorites are an unique source of information about a wide variety of events that occurred very early in the history of the solar system and meteorite fall statistics are frequently used by planetary scientists to approximate the true flux of meteorites on the Earth.
Well documented meteorite falls provide the best available measure of the relative abundances of the different types of meteorite that survive their fall to Earth. The aim of statistical studies is to obtain reliable alues for the influx of meteorite falls and their mass and the constitution of the meteoritic flux. Wickman and Palmer [1] have shown that statistics based on witnessed falls and chance recoveries are fraught with difficulties, and generally rely on ad hoc assumptions about how the distribution of human populations around the world, and their varying levels of education, affect the probability of meteorite recognition and recovery.
This article lists by chronological order every meteor fall observed in Morocco and well documented. All those objects have been watched by eyewitnesses, as it moved in the atmosphere or touched the ground. At the end of May 2012, thirteen official records for observed meteorite falls from Morocco. Moroccan falls are listed and their geographical distribution is shown in Fig. 1.

1. Meteorites
The list by chronological order of all meteor falls observed in Morocco and documented (Fig. 2). All those objects have been watched by eyewitnesses and all last Moroccan falls have been recovered by hunters that spend a lot of time searching meteorites especially in the desert.
1-Douar Mghila. (1932, Ordinary chondrite LL6), some kind of a rocket, from East to west, has been seen through the sky. It has been accompanied with a detonation that we compared with a gun and was heard 10 km from the region, where fell forty stones. According to Captain Larcher, who has witnessed this phenomenon, it occurred 4 km east of Beni Mellal (Douar Mghila) [2].  10-Aoussred. (2012, Carbonaceous chondrite CH), according to one of the three eyewitnesses to the spectacle offered by the entry into the atmosphere of the meteorite, the first ball was white orange before turning red, illuminating the entire area and breaking into pieces after a large explosion. The first fragment was discovered by a soldier who then contacted A. Ibhi, professor at the University Ibn Zohr Agadir [9].

Strewn field
In these 10 falls only two who beneficed study strewn field, Tissint and Tamdakht meteorites (Fig. 3).The Tissint strewn field of this meteorite fall extends at least 15 km from the west-north-west to east-south-east, which is also the flight direction of the meteorite after the observations of the nomads. More than 50 fragments of Tissint meteorite weighing about 20 kg have been recovered from the strewnfield of 60 km 2 area [8].
Approximate trajectory of the Tamdaght strewn field, according to eye witness reports and meteorite find location according to finder's GPS data given in red, is about 25 km long and 2 km wide [6]. The horizontal trajectory, shallow impact pits in the loose gravel soil and the total destruction of masses that did not impact rock but clay surfaces, may provide evidence that the meteorites did retain at least some of their cosmic velocity until they hit the ground at an altitude of 1500 meters.

3. Meteors
The falls of Breja, Nzala and Taouz (Fig. 1) by opposition to the other witnessed falls, raises a problem in the exactness of the statements which relate to it. In spite of eyewitnesses' presence, it always misses in the declaration of this fall the essential elements as the exact coordinates and even the precise day of the fall. As the meteors observations are not precise, the research is not always successful and they can spend weeks and months in the field without recovering the meteorite. While there will always be an element of luck involved in

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ILCPA Volume 17 meteorite fall recovery, a nighttime fireball, after all, will be visible over a much larger geographical region than that in which the meteorite physically falls.  (Table 1), showing the name of the meteorite, the date it fell, the place of fall, and the type of meteorite. Also, meteors are named after the place they fell.

STATISTICAL STUDY OF OBSERVED METEORITE FALLS IN MOROCCO
In Morocco there have been a total of 10 meteorite falls in the time interval 1932 to 2012. It represent only 0.011 % of the Moroccan declared meteorites. The first fall in Morocco was the Douar Mghila meteorite (LL6, 1161 grams; Table 1); the last fall was the Aoussred meteorite (CH, 370 grams; Table 1). The Morocco meteorite fall recovery rate, during the past 80 years, is low 0.11 falls per year on average (or approximately one fall recovery per 10 year time interval, or equivalently, 0.1 fall per year per 2.11 km 2 ). The reasons why so few meteorite falls are recovered per year are no-doubt many and complex. Rasmussen [10] has discussed a number of the possible reasons why the meteorite recovery rate and the documentation of fireball observations Worldwide (have varied with time). A short list of possible factors includes the non-uniform distribution of people, the required development of a scholarly community interested in investigating falls and wars. The list is not quite endless, but it could certainly go on to include geographical conditions in the fall area and weather factors [11].

DISCUSSION AND CONCLUSION
Observed meteorite falls are interesting for several reasons. Material from observed falls has not been subjected to terrestrial weathering, making the find a better candidate for scientific study. Historically, observed falls were the most compelling evidence supporting the extraterrestrial origin of meteorites. Furthermore, observed fall discoveries are a better representative sample of the types of meteorites which fall to Earth.
Ten observed falls have been recovered in Morocco. The earliest well-documented meteorite fall occurred in 1932 near Douar Mghila from which hundreds of stones were collected [2]. The most recently recovered fall, a single stone weighing 270 grams, occurred on 20 May, 2012 at Aoussred in Morocco western Sahar [9]. The authenticated observed falls comprise eight ordinary chondrites (Four of type LL, three of type H and one of type EH), one carbonaceous chondrite and one Shergottite basaltic achondrite.
A number of other fresh meteorite recoveries in Morocco have been linked to witnessed fireballs (e.g., Breja, Nzala and Taouz), these meteorites were found or recognized some time after the reported events and their dates of fall have to be considered doubtful.
Most Morocco meteorites that remain in the country are held in a few institutional collections. The largest collection of Morocco meteorites is held by the Department of Geology in Ibn Zohr University [12,13].