Elephant Moraine 79001, also known as EETA 79001, is a

Martian Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. It became the most popular celestial object in fiction in the late 1800s as the Moon was evidently lifeless. At the time, the pred ...

meteorite. It was found in

Elephant Moraine Elephant Moraine () is an isolated moraine, long, located west of Reckling Peak, to the west of the head of Mawson Glacier in Victoria Land, Antarctica. The moraine, described in some reports as an ice core moraine, is situated along a long, narro ...

, in the

Antarctic The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...

during the 1979–1980 collecting season. EETA79001(S80-37633)

Meteorite Impact and ejection of Martian Meteorite

The meteorite is classified as a

shergottite A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. , 277 meteorites had been classified as Martian, less than half a percen ...

and is primarily

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

ic in composition. EETA 79001 is the second largest

meteorite found on Earth, at approximately 7900 grams; only the Zagami meteorite is larger. It is a very young rock, by geologic standards, dating to only about 180 million years ago, and was ejected from the Martian surface about 600 thousand years ago.

Discovery

EETA 79001 was discovered at the Elephant Moraine, near Reckling Peak, Victoria Land, Antarctica. It was especially significant due to the fact that it had glass inclusions that were found to contain rare nitrogen isotopic compositions. These same compositions were measured in the Martian atmosphere by the Viking spacecraft in 1976. This match was some of the first crucial evidence to positively identify the EETA 79001 meteorite, and others of its class, to be of Martian origin. EETA 79001 was considered to be proven of Martian origin, after much debate, in 1985 by R.O. Pepin by comparing and expanding findings of the Viking and further isotopic analysis of EETA 79001. Stony Martian meteorites, as a whole, are described as being part of the "SNC" group of rocks. This stands for

nakhlite Nakhlites are a group of Martian meteorites, named after the first one, Nakhla meteorite. Nakhlites are igneous rocks that are rich in augite and were formed from basaltic magma about 1.3 billion years ago. They contain augite and olivine crysta ...

s, and

chassignite A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. , 277 meteorites had been classified as Martian, less than half a percen ...

s. These meteorites are distinguished by their shared isotopic compositions which are common with Martian composition, and differ from Earth compositions.Meteoritical Bulletin Database
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Macroscopic descriptions

The meteorite is made up of two distinct lithologies, designated as lithology A and lithology B. Lithology B is an igneous melt, almost certainly originating deep in the Martian crust. Lithology A has some uncertainty associated with it, but appears to be made up of shocked, impact melt from the collision that caused the ejection of EETA 79001. The meteorite is a nearly completely crystalline rock, with a composition typical of volcanic lava crystallized from molten silicate. The sample closely resembles that of basalts collected from Earth and the Moon. Close examination of this sample shows glassy feldspar, which can be shown to have formed under unique conditions, common with impact shock. This glass retains its original structure, showing evidence for no flow having occurred. This process is likely caused due to intense shock waves, such as a large meteoric impact.

Mineralogical descriptions

The main mass of the meteorite is a shocked

pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

. Large

grains range up to 3.5 mm. A few large

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers quickl ...

s also occur, as large as 2.5 mm. The less abundant lithology, lithology B, resembles fine grained shergotty. The major minerals are

maskelynite Maskelynite is a glassy material found in some meteorites and meteorite impact craters. Typical samples are similar in composition to plagioclase feldspar, and revert to that mineral when melted and recrystallized. It was named after British geolog ...

and

clinopyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

, with small occurrence of

calcium phosphate The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are white ...

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...

silicate In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is al ...

, and

ilmenite Ilmenite is a titanium-iron oxide mineral with the idealized formula . It is a weakly magnetic black or steel-gray solid. Ilmenite is the most important ore of titanium and the main source of titanium dioxide, which is used in paints, printing ...

. Dark glass appears throughout, connected with thin veinlits. This glass is of melted origin.

Importance

Martian meteors

EETA 79001 has been shown to originate from the Martian interior, so holds great importance because of the clues it can provide about the composition and evolution of Mars. It was the first sample that provided conclusive evidence of an origin from Mars. The idea of meteorites ejected from other planets was at first not popular with scientists, as they believed such an impact would completely melt the ejected debris, EETA 79001 showed that while some portion is likely melted from impact, original rock crystals can survive the process. This meteorite is one of only 99 known meteorites discovered on earth, of Martian origin. Martian meteorites were critical in our early understanding of a planet that is both a close neighbor and physically very similar to Earth. Before lander missions, the only physical samples to be analyzed were meteorites ejected from Mars, and impacting on Earth.

Debunked evidence for life on Mars

Carbonate found in EETA 79001 was used as a crucial piece of evidence for potential early life on Mars. It was argued that the most likely formation of the carbonate was in liquid water by

biogenic A biogenic substance is a product made by or of life forms. While the term originally was specific to metabolite compounds that had toxic effects on other organisms, it has developed to encompass any constituents, secretions, and metabolites of p ...

means. Today, scientists believe that the carbonate was likely formed through chemical means, and is likely not related to any life that may or may not have been on Mars.

References

{{reflist Meteorites found in Antarctica Martian meteorites