Heat Shield Rock is a

basketball Basketball is a team sport in which two teams, most commonly of five players each, opposing one another on a rectangular Basketball court, court, compete with the primary objective of #Shooting, shooting a basketball (ball), basketball (appro ...

-sized iron-nickel meteorite found on the

Meridiani Planum Meridiani Planum (alternatively Terra Meridiani) is a large plain straddling the equator of Mars. The plain sits on top of an enormous body of sediments that contains bound water. The iron oxide in the spherules is crystalline (grey) hematite (Fe ...

plain of

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

by the Mars rover ''Opportunity'' in January 2005. Informally referred to as "Heat Shield Rock" by the Opportunity research team, the

meteorite A meteorite is a rock (geology), rock that originated in outer space and has fallen to the surface of a planet or Natural satellite, moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical ...

was formally named Meridiani Planum meteorite by the

Meteoritical Society The Meteoritical Society is a non-profit scholarly organization founded in 1933 to promote research and education in planetary science with emphasis on studies of meteorites and other extraterrestrial materials that further our understanding of th ...

in October 2005 (meteorites are always named after the place where they were found).

Discovery

''Opportunity'' encountered the meteorite entirely by chance, in the vicinity of its own discarded heat shield (hence the name). ''Opportunity'' had been sent to examine the heat shield after exiting the crater

Endurance Endurance (also related to sufferance, forbearance, resilience, constitution, fortitude, persistence, tenacity, steadfastness, perseverance, stamina, and hardiness) is the ability of an organism to exert itself and remain active for a ...

. This was the first meteorite found on another planet and the third found on another Solar System bodytwo others, the millimeter-sized Bench Crater and

Hadley Rille Hadley may refer to: Places Earth Canada * Hadley Bay, on the north of Victoria Island, Nunavut England * Hadley, London, a former civil parish within Barnet Urban District from 1894 to 1965 * Hadley, Shropshire, part of the new town of T ...

meteorites, were found on the

Moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

Analysis

The rock was initially identified as unusual in that it showed, from the analysis with the Mini-TES spectrometer, an infrared spectrum that appeared unusually similar to a reflection of the sky. In-situ measurements of its composition were then made using the APXS, showing the composition to be 93%

Iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

, 7%

nickel Nickel is a chemical element; it has symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive, but large pieces are slo ...

, with trace amounts of

germanium Germanium is a chemical element; it has Symbol (chemistry), symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid or a nonmetal in the carbon group that is chemically ...

(~300 ppm) and

gallium Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, elemental gallium is a soft, silvery metal at standard temperature and pressure. ...

(<100 ppm). Mössbauer spectra show the iron to be primarily in metallic form, confirming its identity as an iron-nickel

, composed of

kamacite Kamacite is an alloy of iron and nickel, which is found on Earth only in meteorites. According to the International Mineralogical Association (IMA) it is considered a proper nickel-rich variety of the mineral native iron. The proportion iron:ni ...

with 5–7% nickel. This is essentially identical to the composition of a typical IAB iron meteorite found on Earth. The surface of the rock shows the ''regmaglypts,'' or pits formed by the ablation of a meteorite during passage through the atmosphere, characteristic of meteorites. The largest dimension of the rock is nearing 31 cm. No attempt was made to drill into the meteorite using the

Rock Abrasion Tool The Rock Abrasion Tool (RAT) is a grinding and brushing installation on NASA’s twin Mars Exploration Rovers, '' Spirit'' (MER-A) and '' Opportunity'' (MER-B), which landed on Mars in January 2004. It was designed, developed and continues to be o ...

(RAT), because testing on iron meteorites on

Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...

showed that the rover's drilling tools would be abraded and damaged. The RAT was designed to drill into ordinary rock, not into iron-nickel alloy.

, the part of Mars where this meteorite was found, is suspected to have once been covered by a layer of material with a thickness of as much as which has been subsequently eroded. However no evidence suggests when it impacted. To survive impact largely undeformed it must have impacted at less than ~1.5 km/s, which sets boundaries on its entry dynamics and Mars' atmosphere at the time it impacted. In any case, the meteorite did not show much sign of

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH) ...

. In the absence of detailed knowledge of the Mars environment, it is not possible to conclude whether it fell recently or not.

Other nickel-iron meteorites found on Mars

Following the identification of Heat Shield Rock as a meteorite, five similar iron meteorites were discovered by ''Opportunity'' (informally named "

Block Island Block Island is an island of the Outer Lands coastal archipelago in New England, located approximately south of mainland Rhode Island and east of Long Island's Montauk Point. The island is coterminous with the town of New Shoreham, Rhode Isl ...

", "Ireland" "

Mackinac Island Mackinac Island ( , ; ; ; ) is an island and resort area, covering in land area, in the U.S. state of Michigan. The name of the island in Odawa is Michilimackinac and "Mitchimakinak" in Ojibwemowin, meaning "Great Turtle". It is located in ...

", " Oileán Ruaidh" and " Shelter island"). Two nickel-iron meteorites were identified by the ''Spirit'' rover (informally named "Allan Hills" and "Zhong Shan"). One nickel-iron meteorite has been identified by the ''Curiosity'' rover, tagged "Lebanon." In addition, several candidate stony meteorites have also been identified on Mars.

Terminology

The term " Martian meteorite" usually refers to something entirely different: meteorites on Earth which are believed to have originated from Mars, a famous example being ALH84001.

Gallery

File:Heat Shield Rock 1.jpg File:Heat Shield Rock.jpg File:Heat Shield Rock, Mars.jpg File:Opportunity - meteorito.png File:Heat Shield Rock2.jpg

References

External links

Nasa's Mars Exploration Program

* ttp://www.jpl.nasa.gov/missions/mer/images.cfm?id=1466 JPL meteorite image
JPL Photojournal entry on meteorite

''Sky & Telescope'' article

Article in ''Meteoritical Bulletin''

Official Mars Rovers site

Planetary Science Research Discoveries article. {{Portal bar, Solar System Rocks on Mars Iron meteorites Meteorites found on Mars Mars Exploration Rover mission 2005 in science