The Thermal Emission Imaging System (THEMIS) is a camera on board the 2001 Mars Odyssey orbiter. It images

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 atm ...

in the visible and

infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from arou ...

parts of the

electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging fro ...

in order to determine the thermal properties of the surface and to refine the distribution of

minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...

on the surface of Mars as determined by the Thermal Emission Spectrometer (TES). Additionally, it helps scientists to understand how the

mineralogy Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the pr ...

of Mars relates to its landforms, and it can be used to search for thermal hotspots in the Martian subsurface. THEMIS is managed from the Mars Space Flight Facility at

Arizona State University Arizona State University (Arizona State or ASU) is a public research university in the Phoenix metropolitan area. Founded in 1885 by the 13th Arizona Territorial Legislature, ASU is one of the largest public universities by enrollment in the ...

and was built by the Santa Barbara Remote Sensing division of Raytheon Technologies Corporation, an American multinational conglomerate headquartered in

Waltham, Massachusetts Waltham ( ) is a city in Middlesex County, Massachusetts, United States, and was an early center for the labor movement as well as a major contributor to the American Industrial Revolution. The original home of the Boston Manufacturing Company, ...

. The instrument is named after

Themis In Greek mythology and religion, Themis (; grc, Θέμις, Themis, justice, law, custom) is one of the twelve Titan children of Gaia and Uranus, and the second wife of Zeus. She is the goddess and personification of justice, divine orde ...

, the goddess of justice in ancient

Greek mythology A major branch of classical mythology, Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of Ancient Greek folklore. These stories concern the Cosmogony, origin and Cosmology#Metaphysical co ...

Infrared camera

THEMIS detects thermal infrared energy emitted by the Martian surface at nine different

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...

s. Eight of these have wavelengths between 6 and 13 micrometers, an ideal region of the

infrared spectrum Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from arou ...

to determine thermal energy patterns characteristic of

silicate minerals Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually cons ...

. The ninth band is at 14.9 micrometers and is used to monitor the

Martian atmosphere The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and no ...

. The shortest infrared wavelength, at 6.78 micrometers, is measured twice in two bands to improve the

signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to the noise power, often expressed in dec ...

. THEMIS is therefore a 10-band instrument that detects nine different wavelength

The

absorption spectrum Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating ...

measured by THEMIS contains two kinds of information:

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

and

emissivity The emissivity of the surface of a material is its effectiveness in emitting energy as thermal radiation. Thermal radiation is electromagnetic radiation that most commonly includes both visible radiation (light) and infrared radiation, which is ...

. The temperature contribution to the measurement dominates the spectrum unless the data is corrected. In effect, a THEMIS infrared image taken during the day will look much like a

shaded relief Terrain cartography or relief mapping is the depiction of the shape of the surface of the Earth on a map, using one or more of several techniques that have been developed. Terrain or relief is an essential aspect of physical geography, and as su ...

map, with slopes facing the sun being bright (hot) and shaded areas being dark (cold). In a THEMIS image taken at night, however, thermophysical properties of the surface can be inferred, such as temperature differences due to the materials'

grain size Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which ref ...

( thermal inertia). The effect of temperature can be removed from THEMIS infrared data by dividing the image by a

black body A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The name "black body" is given because it absorbs all colors of light. A black bod ...

curve. The resulting energy pattern is an emissivity spectrum characteristic of the specific minerals (or other things) found on the surface. The presence of minerals such as

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonate g ...

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 i ...

hydroxide Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of wate ...

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and man ...

s, amorphous

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of th ...

s, and

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from pho ...

s can be determined from THEMIS measurements. In particular, this multi-spectral method allows researchers to detect the presence of minerals that form in water and to understand those minerals in their geological context. The THEMIS infrared camera was designed to be used in conjunction with data from the Thermal Emission Spectrometer (TES), a similar instrument on Mars Global Surveyor. While THEMIS has a very high

spatial resolution In physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resoluti ...

(100 m) with a low spectral resolution of only 10 bands between 6 and 15 micrometers, TES has a low spatial resolution (3×6 km) with very high spectral resolution of 143 bands between 5 and 50 micrometers. The instrument's approach provides data on localized deposits associated with volcanoes, hydrothermal processes, and the alteration of minerals by surface and/or subsurface water. The

Advanced Spaceborne Thermal Emission and Reflection Radiometer The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a Japanese remote sensing instrument onboard the Terra satellite launched by NASA in 1999. It has been collecting data since February 2000. ASTER provides high-res ...

(ASTER), an Earth orbiting instrument on the Terra spacecraft, has used a similar approach to map the distribution of minerals on Earth. Variations in the thermal infrared

false-color False color (or pseudo color) refers to a group of color rendering methods used to display images in color which were recorded in the visible or non-visible parts of the electromagnetic spectrum. A false-color image is an image that depicts ...

image are due to differences in the minerals that make up rocks and soil.

Discovery of a variety of rocks

Hematite region Sinus Meridiani sur Mars

THEMIS found a wide range of igneous rocks and minerals. Some of the rocks were low-silica basalts, high silica

dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...

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 quic ...

basalts, ultramafic (picritic) basalts, and quartz-bearing granitoid rocks. The olivine basalts were present in a variety of locations, such as on crater floors and in some canyon wall layers. The mineral olivine is important because it is common in more primitive

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural s ...

s from the mantle and it weathers quickly when moisture is present. So, if olivine is present, the climate must have been dry since the time that olivine was exposed.

Quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical fo ...

-bearing rocks were found in the central uplifts in craters. Rocks in the central uplifts were probably once buried several kilometers beneath the surface, but raised by the impact process. Rocks of dacite composition show that, within magma chambers, fractional crystallization occurred. In this process, some minerals form crystals, then settle to the bottom of the chamber. Having a variety of rocks increases the chances that some useful/valuable minerals may be found on Mars.

Visible camera

THEMIS has a visible imaging camera that acquires data in five spectral bands, takes images with a spatial resolution of 18 m (59'), and can resolve objects about the size of a

semi-trailer A semi-trailer is a trailer without a front axle. In the United States, the term is also used to refer to the combination of a truck and a semi-trailer; a tractor-trailer. A large proportion of a semi-trailer's weight is supported by a tracto ...

. This resolution is intermediate between large-scale images from the Viking Orbiters (150 to 300 meters per pixel) and the high-resolution images from the Mars Orbiter Camera (MOC) on board Mars Global Surveyor (1.5 to 3 meters per pixel). Visible images from THEMIS are usually close to 20 km wide (12 miles). The THEMIS visible camera's stated purpose is to determine the geological record of past liquid and volcanic environments on Mars. Additionally, this dataset can be used in conjunction with the infrared data to identify potential landing sites for future Mars missions.

Images from the Oxia Palus quadrangle

Image:Oxia Palus erosion.JPG,

Erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is di ...

has created huge pits with steep walls. Picture from

Mars Odyssey ''2001 Mars Odyssey'' is a robotic spacecraft orbiting the planet Mars. The project was developed by NASA, and contracted out to Lockheed Martin, with an expected cost for the entire mission of US$297 million. Its mission is to use spectro ...

THEMIS In Greek mythology and religion, Themis (; grc, Θέμις, Themis, justice, law, custom) is one of the twelve Titan children of Gaia and Uranus, and the second wife of Zeus. She is the goddess and personification of justice, divine orde ...

. Image:Eos Chasma.JPG,

Eos Chasma Eos Chasma is a chasma in the southern part of the Valles Marineris canyon system of the Coprates quadrangle and the Margaritifer Sinus quadrangles of the planet Mars. Eos Chasma’s western floor is mainly composed of an etched massive mater ...

with a Mensa, a flat topped prominence with cliff-like edges, as seen by THEMIS. In many places rock layers are visible. Image:Erosion in Aram Chaos.JPG, Erosion in Aram Chaos, as seen by

. Image:Blocks in Aram.JPG, Blocks in Aram showing possible source of water, as seen by

. Image:Erosion features in Ares Vallis.JPG, Erosion features in Ares Vallis, as seen by

Images from Coprates quadrangle

Image:Nirgal Vallis in Coprates.JPG, Nirgal Vallis that runs in two quadrangles has features looking like those caused by sapping. Picture taken with

. Image:Candor Chasm in Coprates.JPG, False color image of

Candor Chasma Candor Chasma is one of the largest canyons in the Valles Marineris canyon system on Mars. The feature is geographically divided into two halves: East and West Candor Chasmas, respectively. It is unclear how the canyon originally formed; one theor ...

showing locations of hydrated

deposits, as seen by THEMIS. Red colors show rocky places. Greens and blues show sandy, dusty areas. Image:Melas Chasma.JPG,

Melas Chasma Melas Chasma is a canyon on Mars, the widest segment of the Valles Marineris canyon system, located east of Ius Chasma at 9.8°S, 283.6°E in Coprates quadrangle. It cuts through layered deposits that are thought to be sediments from an old lake ...

, as seen by THEMIS. Click on image to see relationship of Melas to other features. Image:Cliff in Candor Chasma.JPG, Cliff in

Plateau, as seen by THEMIS. Click on image to see relationship with other features in Coprates quadrangle. Image:Ganges Chasma.JPG, Cliff in northern wall of

Ganges Chasma Ganges Chasma is a deep canyon at the eastern end of the vast Valles Marineris system on Mars, an offshoot of Capri Chasma, and is in the Coprates quadrangle. It is named after the River Ganges in South Asia. Ganges Chasma is thought to have fo ...

, as seen by THEMIS. Click on image to see relationship with other features in the Coprates quadrangle. Image:Channels West of Echus Chasma.JPG, Channels West of Echus Chasma. The fine pattern of branching stream beds were probably formed from water moving across the surface. Image:Echus Chasma Dendritic Channels.JPG, Dendritic channels on mesa of Echus Chasma. Image is 20 miles wide. Image is in Coprates quadrangle. Image:Melas Chasma channels.JPG, Branching channels on floor of Melas Chasma. Image is in Coprates quadrangle.

Images from Lunae Palus quadrangle

Image:Labeatis Fossae.jpg, Labeatis Fossae, as seen by THEMIS. Image:Labeatis Fossae Close-up.JPG, Close-up view of Labeatis Fossae, as seen by THEMIS. Image:Nanedi Valles.jpg, Nanedi Valles, as seen by THEMIS. Image:Nanedi Valles Close-up.JPG, Nanedi Valles Close-up, as seen by THEMIS.

Images from
Margaritifer Sinus quadrangle The Margaritifer Sinus quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Margaritifer Sinus quadrangle is also referred to as MC-19 (Mars Chart-1 ...

Image:Canyons and Mesas of Aureum Chaos in Oxia Palus.JPG, Huge canyons in Aureum Chaos. Gullies are rare at this latitude. Picture taken by THEMIS. Image:Aureum Chaos from Themis.JPG, Aureum Chaos, as seen from Themis. Image:Iani Chaos.JPG,

Iani Chaos Iani Chaos is a region of chaos terrain at the south end of the outflow channel Ares Vallis, of the Margaritifer Sinus quadrangle (MC-19) region of the planet Mars, centered at approximately ~342°E, 2°S. This is the source region of Ares Valli ...

, as seen by THEMIS. Sand from eroding mesas is covering brighter floor material. Click on image to see relationship of Iani Chaos to other local features. Image:Holden Crater Close-up.JPG, Close-up of Channels on Rim of Holden Crater, as seen by THEMIS. Click on image to see more details.

Images from Phoenicis Lacus quadrangle

Image:Lava tubes Pavonis Mons, Phoenicis Lacus.JPG, Lava tubes were once covered over with

lava Lava is molten or partially molten rock ( magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...

flowing in them, but the roofs have now collapsed and the lava has left. Also, some straight troughs (

graben In geology, a graben () is a depressed block of the crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German, meaning 'ditch' or 'trench'. The word was first used in the geologic cont ...

s) crosscut the

channels. Picture taken by

. Image:Alpine glacier in Phoenicis Lacus.JPG, Ridges on side of Arsia Mons, a large

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ...

, may be

moraine A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice she ...

s dropped by glacial activity Image:Arsia Mons.JPG, Arsia Mons showing its position among other volcanoes as seen by THEMIS. Image:Oti Fossae.jpg, Oti Fossae, as seen by THEMIS. These parallel graben are found on the northeastern side of Arsia Mons; they are in line with the NE/SW trend of the three volcanoes in Tharsis. Image:Oti Fossae Close-up.JPG, Oti Fossae, as seen by THEMIS. These parallel graben are found on the northeastern side of Arsia Mons; they are in line with the NE/SW trend of the three volcanoes in Tharsis.

Images from Hellas quadrangle

Image:Reull Vallis.JPG, Drainage features in Reull Vallis, as seen by

. Click on image to see relationship of Reull Vallis to other features. File:Reull Vallis lineated deposits.jpg, Reull Vallis with lineated floor deposits, as seen by THEMIS. Click on image to see relationship to other features. Image:Reull Vallisl layers.JPG, Layers in Reull Vallis, as seen by THEMIS. Image:Lipik Crater Channels.jpg, Lipik Crater Channels, as seen by

Images from
Memnonia quadrangle The Memnonia quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Memnonia quadrangle is also referred to as MC-16 (Mars Chart-16). The quadrangle ...

Image:Mangala Vallis.JPG, Mangala Vallis with a streamlined island, as seen by

. Image:Minio Vallis.JPG, Minio Vallis, as seen by THEMIS. Minio Vallis is a small river channel near the much larger Mangala Vallis. Image:Sabis Vallis.JPG, Sabis Vallis, as seen by THEMIS. The small channels are joining to form Sabis Vallis. Image:PadusVallis Close-up.JPG, Close-up of Padus Vallis, as seen by THEMIS.

Other Images from THEMIS

Image:Ulysses Patera.JPG, Ulysses Patera in Tharsis quadrangle, showing its location in relation to other volcanoes, as seen by

. Image:Cerberus Fossae from Themis.JPG, Cerberus Fossae, as seen from THEMIS. Image from

Elysium quadrangle The Elysium quadrangle is one of a series of 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Elysium quadrangle is also referred to as MC-15 (Mars Chart-15). The name Elysium ...

. Image:Semeykin Crater Drainage.JPG, Semeykin Crater Drainage, as seen by

. Click on image to see details of beautiful drainage system. Image from Ismenius Lacus quadrangle. Image:Tader Valles.JPG, Tader Valles, as seen by

. Smooth material in channels may be a mantle in the form of dirty snow. Tader Valles is in the Phaethontis quadrangle.

Bopolu crater

File:PIA14995 fig1.png, Context for image File:PIA14995.jpg, Bopolu crater, Mars

Specifications

The Thermal Emission Imaging System weighs 11.2 kilograms (24.7 lb), is 54.5 x 37 x 28.6 cm (21.5 x 14.6 x 11.3 in) and runs on 14 watts of electrical power.

References

External links

THEMIS Specifications

THEMIS instrument site
at

Searchable database of THEMIS data, including detailed information on individual observations

Public data releases of THEMIS data

Maps of Mars images including THEMIS, MOC, HiRISE, CTX, HRSC, and Viking
{{Use American English, date=January 2014 2001 Mars Odyssey Mars imagers