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. 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 ...

in the visible and

infrared Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those ...

parts of the

electromagnetic spectrum The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high ...

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 substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): M ...

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 mineralogy, optical) properties of minerals and mineralized artifact (archaeology), artifacts. Specific s ...

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 university, public research university in Tempe, Arizona, United States. Founded in 1885 as Territorial Normal School by the 13th Arizona Territorial Legislature, the university is o ...

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 Technological and industrial history of the United States, American Industrial Revoluti ...

. The instrument is named after Themis, the goddess of justice in ancient

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

Infrared camera

Hematite region Sinus Meridiani sur Mars

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

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

s. Eight of these have wavelengths between 6 and 13 micrometers, an ideal region of the infrared spectrum 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, the crystalline forms of silica (silicon dio ...

. The ninth band is at 14.9 micrometers and is used to monitor the Martian atmosphere. 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 noise power, often expressed in deci ...

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

The absorption spectrum measured by THEMIS contains two kinds of information:

temperature Temperature is a physical quantity that quantitatively expresses the attribute of hotness or coldness. Temperature is measurement, measured with a thermometer. It reflects the average kinetic energy of the vibrating and colliding atoms making ...

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 n ...

. 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 ...

(

thermal inertia Thermal inertia is a term commonly used to describe the observed delays in a body's temperature response during heat transfers. The phenomenon exists because of a body's ability to both store and transport heat relative to its environment. Sinc ...

). The effect of temperature can be removed from THEMIS infrared data by dividing the image by a black body 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, (), 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 group ...

silicate 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 also used ...

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 water. It ...

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 many ...

s, amorphous

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

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

s, and

phosphate Phosphates are the naturally occurring form of the element phosphorus. 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 orthop ...

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 ''Mars Global Surveyor'' (MGS) was an American Robotic spacecraft, robotic space probe developed by NASA's Jet Propulsion Laboratory. It launched November 1996 and collected data from 1997 to 2006. MGS was a global mapping mission that examined ...

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

Discovery of a variety of rocks

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 minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

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 (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

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 Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

-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 (vehicle), trailer without a front axle. The combination of a semi-trailer and a tractor truck is called a ''semi-trailer truck'' (also known simply as a "semi-trailer", "tractor trailer", or "semi" in the United Sta ...

. 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

(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 Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

has created huge pits with steep walls. Picture from Mars Odyssey THEMIS. Image:Eos Chasma.JPG, Eos Chasma 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 Aram Chaos, centered at 2.6°N, 21.5°W, is a heavily eroded impact crater on Mars. It lies at the eastern end of the large canyon Valles Marineris and close to Ares Vallis. Various geological processes have reduced it to a circular area of cha ...

, as seen by THEMIS. Image:Blocks in Aram.JPG, Blocks in Aram showing possible source of water, as seen by THEMIS. Image:Erosion features in Ares Vallis.JPG, Erosion features in Ares Vallis, as seen by THEMIS

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 Sapping is a term used in siege operations to describe the digging of a covered trench (a "sap") to approach a besieged place without danger from the enemy's fire. (verb) The purpose of the sap is usually to advance a besieging army's position ...

. Picture taken with THEMIS. 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 the ...

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, 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, 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 The Lunae Palus quadrangle is one of a series of list of quadrangles on Mars, 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The quadrangle (geography), quadrangle is also referred to ...

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 list of quadrangles on Mars, 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Margaritifer Sinus quadrangle is also referred ...

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, 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 Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

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 depression (geology), depressed block of the Crust (geology), crust of a planet or moon, bordered by parallel normal faults. Etymology ''Graben'' is a loan word from German language, German, meaning 'ditch' or 't ...

s) crosscut the

channels. Picture taken by THEMIS. Image:Alpine glacier in Phoenicis Lacus.JPG, Ridges on side of Arsia Mons, a large

volcano A volcano is commonly defined as a vent or fissure 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 oft ...

, may be

moraine A moraine is any accumulation of unconsolidated debris (regolith and Rock (geology), 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 gla ...

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 THEMIS. 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 THEMIS.

Images from Memnonia quadrangle

Image:Mangala Vallis.JPG, Mangala Vallis with a streamlined island, as seen by THEMIS. 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 The Tharsis quadrangle is one of a series of 30 list of quadrangles on Mars, quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Tharsis quadrangle is also referred to as MC-9 (Mars Chart- ...

, showing its location in relation to other volcanoes, as seen by THEMIS. Image:Cerberus Fossae from Themis.JPG, Cerberus Fossae, as seen from THEMIS. Image from Elysium quadrangle. Image:Semeykin Crater Drainage.JPG, Semeykin Crater Drainage, as seen by THEMIS. Click on image to see details of beautiful drainage system. Image from

Ismenius Lacus quadrangle The Ismenius Lacus quadrangle is one of a series of list of quadrangles on Mars, 30 quadrangle maps of Mars used by the United States Geological Survey (USGS) Astrogeology Research Program. The Quadrangle (geography), quadrangle is located in th ...

. Image:Tader Valles.JPG, Tader Valles, as seen by THEMIS. 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 Articles containing video clips Mars imagers