Nakhla meteorite

Nakhla meteorite

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Nakhla is a famous martian meteorite fallen in Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

 in 1911.

History


It fell to Earth on June 28, 1911, at approximately 09:00, in the Nakhla region of Abu Hommos, Alexandria
Alexandria
Alexandria is the second-largest city of Egypt, with a population of 4.1 million, extending about along the coast of the Mediterranean Sea in the north central part of the country; it is also the largest city lying directly on the Mediterranean coast. It is Egypt's largest seaport, serving...

, Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

. Many people witnessed its explosion in the upper atmosphere before the meteorite fell to Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

 in an area of 4.5 km in diameter, and about forty pieces were recovered ; the fragments were buried in the ground up to a meter deep.
From an estimated original weight of 10 kg (22 pounds), recovered fragments ranged in weight from 20g to 1813g.

The Nakhla dog


One fragment of the meteorite was said to have landed on a dog, as observed by a farmer named Mohammed Ali Effendi Hakim in the village of Denshal, near Nakhla, supposedly vaporizing the animal instantly. Since no remains of the dog were recovered and there were no other eyewitness to the dog's demise, this story remains apocryphal. However, the story of the Nakhla dog has become something of a legend among astronomers.

Classification


It is the prototypical example of a Nakhlite type meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

 of the SNC Group of Mars meteorite
Mars meteorite
A martian meteorite is a rock that formed on the planet Mars, was ejected from Mars by the impact of an asteroid or comet, and landed on the Earth. Of over 53000 meteorites that have been found on Earth, 99 are martian...

s.

Martian origins


Thirty-four meteorites thought to have originated from Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 have been catalogued from around the world, including the Nakhla meteorite. These are considered to have been ejected
Ejecta
Ejecta can mean:*In volcanology, particles that came out of a volcanic vent, traveled through the air or under water, and fell back on the ground surface or on the ocean floor...

 by the impact of another large body colliding with the Martian surface. They then travelled through the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...

 for an unknown period of time before penetrating the Earth's atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...

.

Signs of water


Nakhla is the first Martian meteorite to show signs of aqueous processes on Mars. The rock contains carbonates and hydrous minerals, formed by chemical reactions in water. In addition, the rock was exposed to water after it formed, which caused secondary accumulations of minerals. The carbonates contain more 13C than rocks formed on Earth, indicating Martian origin.

Signs of life


In March 1999, after receiving part of the meteorite from the British Museum
British Museum
The British Museum is a museum of human history and culture in London. Its collections, which number more than seven million objects, are amongst the largest and most comprehensive in the world and originate from all continents, illustrating and documenting the story of human culture from its...

 in 1998 , a team from NASA's
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 Johnson Space Center examined the Nakhla meteorite using an optical microscope
Optical microscope
The optical microscope, often referred to as the "light microscope", is a type of microscope which uses visible light and a system of lenses to magnify images of small samples. Optical microscopes are the oldest design of microscope and were possibly designed in their present compound form in the...

 and a powerful scanning electron microscope
Scanning electron microscope
A scanning electron microscope is a type of electron microscope that images a sample by scanning it with a high-energy beam of electrons in a raster scan pattern...

 (SEM), revealing biomorph
Biomorph
Biomorph may refer to:*A shape resembling that of a living organism , though not necessarily of biotic origin*One of the virtual creatures in a computer simulation described by Richard Dawkins in his book The Blind Watchmaker...

ic forms of a limited size range, among other features. London's Natural History Museum
Natural History Museum
The Natural History Museum is one of three large museums on Exhibition Road, South Kensington, London, England . Its main frontage is on Cromwell Road...

, which holds several intact fragments of the meteorite, allowed NASA researchers to break one open in 2006, providing fresh samples, relatively free from Earth-sourced contamination. These scientists found an abundance of complex carbonaceous material occupying dendritic pores and channels in the rock, reminiscent of the effects of bacteria observed in rocks on Earth.

A debate was opened by some at the 37th Lunar and Planetary Science Conference in March 2006 in Houston, Texas
Houston, Texas
Houston is the fourth-largest city in the United States, and the largest city in the state of Texas. According to the 2010 U.S. Census, the city had a population of 2.1 million people within an area of . Houston is the seat of Harris County and the economic center of , which is the ...

, postulating that the carbon-rich content within the pores of the rocks hinted at the remains of living matter. However, because carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

 is the fourth most abundant element in the universe (after hydrogen, helium, and oxygen), the presence of shapes reminiscent of living organisms has itself proved insufficient to convince all scientists that bacteria once lived on Mars.

Amino acids within the meteorite


In 1999, various amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

s were isolated from the meteorite fragment at Johnson Space Center. Among them were aspartic acid
Aspartic acid
Aspartic acid is an α-amino acid with the chemical formula HOOCCHCH2COOH. The carboxylate anion, salt, or ester of aspartic acid is known as aspartate. The L-isomer of aspartate is one of the 20 proteinogenic amino acids, i.e., the building blocks of proteins...

, glutamic acid
Glutamic acid
Glutamic acid is one of the 20 proteinogenic amino acids, and its codons are GAA and GAG. It is a non-essential amino acid. The carboxylate anions and salts of glutamic acid are known as glutamates...

, glycine
Glycine
Glycine is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its 'side chain', glycine is the smallest of the 20 amino acids commonly found in proteins. Its codons are GGU, GGC, GGA, GGG cf. the genetic code.Glycine is a colourless, sweet-tasting crystalline solid...

, alanine
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...

s, and butyric acid
Butyric acid
Butyric acid , also known under the systematic name butanoic acid, is a carboxylic acid with the structural formula CH3CH2CH2-COOH. Salts and esters of butyric acid are known as butyrates or butanoates...

. However, it is not clear whether they were originally from the meteorite or the product of terrestrial contamination.

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