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 (appr ...

-sized iron-nickel meteorite found on the

Meridiani Planum The Meridiani Planum (alternately Meridiani plain, Meridiani plains, Terra Meridiani, or Terra Meridiani plains) is either a large plain straddling the equator of Mars and covered with a vast number of spherules containing a lot of iron oxide or ...

plain of

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

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 solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon. When the original object ...

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 the ...

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 In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is al ...

(hence the name). ''Opportunity'' had been sent to examine the heat shield after exiting the crater

Endurance Endurance (also related to sufferance, resilience, constitution, fortitude, and hardiness) is the ability of an organism to exert itself and remain active for a long period of time, as well as its ability to resist, withstand, recover from an ...

. 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 meteorites, were found on the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

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 :''APXS is also an abbreviation for APache eXtenSion tool, an extension for Apache web servers.'' An alpha particle X-ray spectrometer (APXS) is a spectrometer that analyses the chemical element composition of a sample from scattered alpha part ...

, showing the composition to be 93%

Iron Iron () is a chemical element with symbol Fe (from la, ferrum) 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, right in ...

, 7%

nickel Nickel is a chemical element with 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 slow t ...

, with trace amounts of

germanium Germanium is a chemical element with the symbol Ge and atomic number 32. It is lustrous, hard-brittle, grayish-white and similar in appearance to silicon. It is a metalloid in the carbon group that is chemically similar to its group neighbors ...

(~300 ppm) and

gallium Gallium is a chemical element with the Symbol (chemistry), symbol Ga and atomic number 31. Discovered by France, French chemist Paul-Émile Lecoq de Boisbaudran in 1875, Gallium is in boron group, group 13 of the periodic table and is similar to ...

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

, composed of kamacite 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 ...

(RAT), because testing on iron meteorites on

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...

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( ...

. 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 in the U.S. state of Rhode Island located in Block Island Sound approximately south of the mainland and east of Montauk Point, Long Island, New York, named after Dutch explorer Adriaen Block. It is part of Washingto ...

", "Ireland" "

Mackinac Island Mackinac Island ( ; french: Île Mackinac; oj, Mishimikinaak ᒥᔑᒥᑭᓈᒃ; otw, Michilimackinac) 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 ...

", " 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