MOMENT OF INERTIA FACTOR
SIDEREAL ROTATION PERIOD
24h 37m 22s
EQUATORIAL ROTATION VELOCITY
868.22 km/h (241.17 m/s)
25.19° to its orbital plane
NORTH POLE RIGHT ASCENSION
21h 10m 44s
NORTH POLE DECLINATION
0.170 (geometric )
0.25 (Bond )
+1.6 to −3.0
0.636 (0.4–0.87) kPa
COMPOSITION BY VOLUME
* 95.97% carbon dioxide
* 1.93% argon
* 1.89% nitrogen
* 0.146% oxygen
* 0.0557% carbon monoxide
MARS is the fourth planet from the
Sun and the second-smallest planet
Solar System after Mercury . In English,
Mars carries a name of
the Roman god of war , and is often referred to as the "RED PLANET"
because the reddish iron oxide prevalent on its surface gives it a
reddish appearance that is distinctive among the astronomical bodies
visible to the naked eye.
Mars is a terrestrial planet with a thin
atmosphere , having surface features reminiscent both of the impact
craters of the
Moon and the valleys, deserts, and polar ice caps of
The rotational period and seasonal cycles of
Mars are likewise
similar to those of Earth, as is the tilt that produces the seasons.
Mars is the site of
Olympus Mons , the largest volcano and
second-highest known mountain in the
Solar System , and of Valles
Marineris , one of the largest canyons in the Solar System. The smooth
Borealis basin in the northern hemisphere covers 40% of the planet and
may be a giant impact feature.
Mars has two moons , Phobos and
Deimos , which are small and irregularly shaped. These may be captured
asteroids , similar to
5261 Eureka , a
Mars trojan .
There are ongoing investigations assessing the past habitability
potential of Mars, as well as the possibility of extant life . Future
astrobiology missions are planned, including the
Mars 2020 and ExoMars
rovers. Liquid water cannot exist on the surface of
Mars due to
low atmospheric pressure, which is less than 1% of the Earth's,
except at the lowest elevations for short periods. The two polar ice
caps appear to be made largely of water. The volume of water ice in
the south polar ice cap, if melted, would be sufficient to cover the
entire planetary surface to a depth of 11 meters (36 ft). In November
NASA reported finding a large amount of underground ice in the
Utopia Planitia region of Mars. The volume of water detected has been
estimated to be equivalent to the volume of water in
Lake Superior .
Mars can easily be seen from
Earth with the naked eye, as can its
reddish coloring. Its apparent magnitude reaches −2.91, which is
surpassed only by
Venus , the Moon, and the Sun. Optical
ground-based telescopes are typically limited to resolving features
about 300 kilometers (190 mi) across when
Mars are closest
because of Earth's atmosphere.
* 1 Physical characteristics
* 1.1 Internal structure
* 1.2 Surface geology
* 1.3 Soil
* 1.4 Hydrology
* 1.4.1 Polar caps
* 1.5 Geography and naming of surface features
* 1.5.1 Map of quadrangles
* 1.5.2 Impact topography
* 1.5.3 Volcanoes
* 1.5.4 Tectonic sites
* 1.5.5 Holes
* 1.7 Climate
* 2 Orbit and rotation
* 3 Habitability and search for life
* 3.1 Search for life
* 4 Moons
* 5 Exploration
* 5.1 Future
Astronomy on Mars
* 7 Viewing
* 7.1 Closest approaches
* 7.1.1 Relative
* 7.1.2 Absolute, around the present time
* 8 Historical observations
* 8.1 Ancient and medieval observations
* 9 In culture
* 9.1 Intelligent "Martians"
* 10 See also
* 11 Notes
* 12 References
* 13 External links
Mars is approximately half the diameter of
Earth with a surface area
only slightly less than the total area of Earth's dry land.
less dense than Earth, having about 15% of Earth's volume and 11% of
Earth's mass , resulting in about 38% of Earth's surface gravity. The
red-orange appearance of the
Martian surface is caused by iron(III)
oxide , or rust. It can look like butterscotch; other common surface
colors include golden, brown, tan, and greenish, depending on the
minerals present. Comparison:
Mars Play media
Animation (00:40) showing major features of
Mars Play media Video
(01:28) showing how three
NASA orbiters mapped the gravity field of
Mars has differentiated into a dense metallic core
overlaid by less dense materials. Current models of its interior
imply a core with a radius of about 1,794 ± 65 kilometers (1,115 ±
40 mi), consisting primarily of iron and nickel with about 16–17%
sulfur . This iron(II) sulfide core is thought to be twice as rich in
lighter elements as Earth's. The core is surrounded by a silicate
mantle that formed many of the tectonic and volcanic features on the
planet, but it appears to be dormant. Besides silicon and oxygen, the
most abundant elements in the
Martian crust are iron, magnesium ,
aluminum , calcium , and potassium . The average thickness of the
planet's crust is about 50 km (31 mi), with a maximum thickness of 125
km (78 mi). Earth's crust averages 40 km (25 mi).
Geology of Mars
Geology of Mars
Mars is a terrestrial planet that consists of minerals containing
silicon and oxygen , metals , and other elements that typically make
up rock . The surface of
Mars is primarily composed of tholeiitic
basalt , although parts are more silica -rich than typical basalt and
may be similar to andesitic rocks on
Earth or silica glass. Regions of
low albedo suggest concentrations of plagioclase feldspar , with
northern low albedo regions displaying higher than normal
concentrations of sheet silicates and high-silicon glass. Parts of the
southern highlands include detectable amounts of high-calcium
pyroxenes . Localized concentrations of hematite and olivine have been
found. Much of the surface is deeply covered by finely grained
iron(III) oxide dust. Geologic map of
USGS , 2014)
Mars has no evidence of a structured global magnetic field ,
observations show that parts of the planet's crust have been
magnetized, suggesting that alternating polarity reversals of its
dipole field have occurred in the past. This paleomagnetism of
magnetically susceptible minerals is similar to the alternating bands
found on Earth\'s ocean floors . One theory, published in 1999 and
re-examined in October 2005 (with the help of the
Mars Global Surveyor
), is that these bands suggest plate tectonic activity on
billion years ago, before the planetary dynamo ceased to function and
the planet's magnetic field faded.
It is thought that, during the Solar System\'s formation ,
created as the result of a stochastic process of run-away accretion of
material from the protoplanetary disk that orbited the Sun.
many distinctive chemical features caused by its position in the Solar
System. Elements with comparatively low boiling points, such as
chlorine , phosphorus , and sulphur , are much more common on Mars
than Earth; these elements were probably pushed outward by the young
Sun's energetic solar wind .
After the formation of the planets, all were subjected to the
Late Heavy Bombardment
Late Heavy Bombardment ". About 60% of the surface of Mars
shows a record of impacts from that era, whereas much of the
remaining surface is probably underlain by immense impact basins
caused by those events. There is evidence of an enormous impact basin
in the northern hemisphere of Mars, spanning 10,600 by 8,500 km (6,600
by 5,300 mi), or roughly four times the size of the Moon's South Pole
– Aitken basin , the largest impact basin yet discovered. This
theory suggests that
Mars was struck by a
Pluto -sized body about four
billion years ago. The event, thought to be the cause of the Martian
hemispheric dichotomy , created the smooth
Borealis basin that covers
40% of the planet. Artist's impression of how
Mars may have
looked four billion years ago
The geological history of
Mars can be split into many periods, but
the following are the three primary periods:
* NOACHIAN PERIOD (named after
Noachis Terra ): Formation of the
oldest extant surfaces of Mars, 4.5 to 3.5 billion years ago. Noachian
age surfaces are scarred by many large impact craters. The Tharsis
bulge, a volcanic upland, is thought to have formed during this
period, with extensive flooding by liquid water late in the period.
* HESPERIAN PERIOD (named after
Hesperia Planum ): 3.5 to between
3.3 and 2.9 billion years ago. The
Hesperian period is marked by the
formation of extensive lava plains.
* AMAZONIAN PERIOD (named after
Amazonis Planitia ): between 3.3 and
2.9 billion years ago to the present. Amazonian regions have few
meteorite impact craters, but are otherwise quite varied. Olympus Mons
formed during this period, with lava flows elsewhere on Mars.
Geological activity is still taking place on Mars. The Athabasca
Valles is home to sheet-like lava flows created about 200 Mya . Water
flows in the grabens called the
Cerberus Fossae occurred less than 20
Mya, indicating equally recent volcanic intrusions. On February 19,
2008, images from the
Mars Reconnaissance Orbiter showed evidence of
an avalanche from a 700-metre-high (2,300 ft) cliff.
Martian soil Exposure of silica-rich dust
uncovered by the
The Phoenix lander returned data showing
Martian soil to be slightly
alkaline and containing elements such as magnesium , sodium ,
potassium and chlorine . These nutrients are found in soils on Earth,
and they are necessary for growth of plants. Experiments performed by
the lander showed that the
Martian soil has a basic pH of 7.7, and
contains 0.6% of the salt perchlorate .
Streaks are common across
Mars and new ones appear frequently on
steep slopes of craters, troughs, and valleys. The streaks are dark at
first and get lighter with age. The streaks can start in a tiny area,
then spread out for hundreds of metres. They have been seen to follow
the edges of boulders and other obstacles in their path. The commonly
accepted theories include that they are dark underlying layers of soil
revealed after avalanches of bright dust or dust devils . Several
other explanations have been put forward, including those that involve
water or even the growth of organisms.
Water on Mars
Liquid water cannot exist on the surface of
Mars due to low
atmospheric pressure, which is less than 1% that of Earth's, except
at the lowest elevations for short periods. The two polar ice caps
appear to be made largely of water. The volume of water ice in the
south polar ice cap, if melted, would be sufficient to cover the
entire planetary surface to a depth of 11 meters (36 ft). A
permafrost mantle stretches from the pole to latitudes of about 60°.
Large quantities of water ice are thought to be trapped within the
thick cryosphere of Mars. Radar data from
Mars Express and the Mars
Orbiter show large quantities of water ice at both
poles (July 2005) and at middle latitudes (November 2008). The
Phoenix lander directly sampled water ice in shallow
Martian soil on
July 31, 2008. Photomicrograph by Opportunity showing a gray
hematite concretion , nicknamed "blueberries", indicative of the past
existence of liquid water
Landforms visible on
Mars strongly suggest that liquid water has
existed on the planet's surface. Huge linear swathes of scoured
ground, known as outflow channels , cut across the surface in about 25
places. These are thought to be a record of erosion caused by the
catastrophic release of water from subsurface aquifers, though some of
these structures have been hypothesized to result from the action of
glaciers or lava. One of the larger examples, Ma\'adim Vallis is 700
km (430 mi) long, much greater than the Grand Canyon, with a width of
20 km (12 mi) and a depth of 2 km (1.2 mi) in places. It is thought to
have been carved by flowing water early in Mars's history. The
youngest of these channels are thought to have formed as recently as
only a few million years ago. Elsewhere, particularly on the oldest
areas of the
Martian surface, finer-scale, dendritic networks of
valleys are spread across significant proportions of the landscape.
Features of these valleys and their distribution strongly imply that
they were carved by runoff resulting from precipitation in early Mars
history. Subsurface water flow and groundwater sapping may play
important subsidiary roles in some networks, but precipitation was
probably the root cause of the incision in almost all cases.
Along crater and canyon walls, there are thousands of features that
appear similar to terrestrial gullies . The gullies tend to be in the
highlands of the southern hemisphere and to face the Equator; all are
poleward of 30° latitude. A number of authors have suggested that
their formation process involves liquid water, probably from melting
ice, although others have argued for formation mechanisms involving
carbon dioxide frost or the movement of dry dust. No partially
degraded gullies have formed by weathering and no superimposed impact
craters have been observed, indicating that these are young features,
possibly still active. Other geological features, such as deltas and
alluvial fans preserved in craters, are further evidence for warmer,
wetter conditions at an interval or intervals in earlier
Such conditions necessarily require the widespread presence of crater
lakes across a large proportion of the surface, for which there is
independent mineralogical, sedimentological and geomorphological
evidence. Composition of "Yellowknife Bay" rocks . Rock veins
are higher in calcium and sulfur than "portage" soil (Curiosity , APXS
Further evidence that liquid water once existed on the surface of
Mars comes from the detection of specific minerals such as hematite
and goethite , both of which sometimes form in the presence of water.
In 2004, Opportunity detected the mineral jarosite . This forms only
in the presence of acidic water, which demonstrates that water once
existed on Mars. More recent evidence for liquid water comes from the
finding of the mineral gypsum on the surface by NASA's
Opportunity in December 2011. It is believed that the amount of
water in the upper mantle of Mars, represented by hydroxyl ions
contained within the minerals of Mars's geology, is equal to or
greater than that of
Earth at 50–300 parts per million of water,
which is enough to cover the entire planet to a depth of 200–1,000 m
In 2005, radar data revealed the presence of large quantities of
water ice at the poles and at mid-latitudes. The
Mars rover Spirit
sampled chemical compounds containing water molecules in March 2007.
The Phoenix lander directly sampled water ice in shallow
on July 31, 2008.
On March 18, 2013,
NASA reported evidence from instruments on the
Curiosity rover of mineral hydration , likely hydrated calcium sulfate
, in several rock samples including the broken fragments of "Tintina"
rock and "Sutton Inlier" rock as well as in veins and nodules in other
rocks like "Knorr" rock and "Wernicke" rock . Analysis using the
rover's DAN instrument provided evidence of subsurface water,
amounting to as much as 4% water content, down to a depth of 60 cm (24
in), during the rover's traverse from the
Bradbury Landing site to the
Yellowknife Bay area in the Glenelg terrain. In September 2015, NASA
announced that they had found conclusive evidence of hydrated brine
flows on recurring slope lineae , based on spectrometer readings of
the darkened areas of slopes. These observations provided
confirmation of earlier hypotheses based on timing of formation and
their rate of growth, that these dark streaks resulted from water
flowing in the very shallow subsurface. The streaks contain hydrated
salts, perchlorates, which have water molecules in their crystal
structure. The streaks flow downhill in
Martian summer, when the
temperature is above −23 degrees Celsius, and freeze at lower
temperatures. On September 28, 2015,
NASA announced the presence of
briny flowing salt water on the
Researchers believe that much of the low northern plains of the
planet were covered with an ocean hundreds of meters deep, though this
remains controversial. In March 2015, scientists stated that such an
ocean might have been the size of Earth's
Arctic Ocean . This finding
was derived from the ratio of water to deuterium in the modern Martian
atmosphere compared to that ratio on Earth. The amount of Martian
deuterium is eight times the amount that exists on Earth, suggesting
Mars had significantly higher levels of water. Results
from the Curiosity rover had previously found a high ratio of
Gale Crater , though not significantly high enough to
suggest the former presence of an ocean. Other scientists caution that
these results have not been confirmed, and point out that Martian
climate models have not yet shown that the planet was warm enough in
the past to support bodies of liquid water.
Martian polar ice caps North polar early summer
ice cap (1999) South polar midsummer ice cap (2000)
Mars has two permanent polar ice caps. During a pole's winter, it
lies in continuous darkness, chilling the surface and causing the
deposition of 25–30% of the atmosphere into slabs of CO2 ice (dry
ice ). When the poles are again exposed to sunlight, the frozen CO2
sublimes . These seasonal actions transport large amounts of dust and
water vapor, giving rise to Earth-like frost and large cirrus clouds .
Clouds of water-ice were photographed by the
Opportunity rover in
The caps at both poles consist primarily (70%) of water ice. Frozen
carbon dioxide accumulates as a comparatively thin layer about one
metre thick on the north cap in the northern winter only, whereas the
south cap has a permanent dry ice cover about eight metres thick. This
permanent dry ice cover at the south pole is peppered by flat floored,
shallow, roughly circular pits , which repeat imaging shows are
expanding by meters per year; this suggests that the permanent CO2
cover over the south pole water ice is degrading over time. The
northern polar cap has a diameter of about 1,000 km (620 mi) during
Mars summer, and contains about 1.6 million cubic
kilometres (380,000 cu mi) of ice, which, if spread evenly on the cap,
would be 2 km (1.2 mi) thick. (This compares to a volume of 2.85
million cubic kilometres (680,000 cu mi) for the Greenland ice sheet
.) The southern polar cap has a diameter of 350 km (220 mi) and a
thickness of 3 km (1.9 mi). The total volume of ice in the south
polar cap plus the adjacent layered deposits has been estimated at 1.6
million cubic km. Both polar caps show spiral troughs, which recent
SHARAD ice penetrating radar has shown are a result of
katabatic winds that spiral due to the
Coriolis Effect .
The seasonal frosting of areas near the southern ice cap results in
the formation of transparent 1-metre-thick slabs of dry ice above the
ground. With the arrival of spring, sunlight warms the subsurface and
pressure from subliming CO2 builds up under a slab, elevating and
ultimately rupturing it. This leads to geyser-like eruptions of CO2
gas mixed with dark basaltic sand or dust. This process is rapid,
observed happening in the space of a few days, weeks or months, a rate
of change rather unusual in geology – especially for Mars. The gas
rushing underneath a slab to the site of a geyser carves a
spiderweb-like pattern of radial channels under the ice, the process
being the inverted equivalent of an erosion network formed by water
draining through a single plughole.
GEOGRAPHY AND NAMING OF SURFACE FEATURES
Geography of Mars For more on how geographic
references are determined, see
Geodetic datum . See also:
Category:Surface features of
Mars A MOLA -based topographic map
showing highlands (red and orange) dominating the southern hemisphere
of Mars, lowlands (blue) the northern. Volcanic plateaus delimit
regions of the northern plains, whereas the highlands are punctuated
by several large impact basins. These new impact craters on
Mars occurred sometime between 2008 and 2014, as detected from orbit
Although better remembered for mapping the Moon, Johann Heinrich
Wilhelm Beer were the first "areographers". They began by
establishing that most of Mars's surface features were permanent and
by more precisely determining the planet's rotation period. In 1840,
Mädler combined ten years of observations and drew the first map of
Mars. Rather than giving names to the various markings, Beer and
Mädler simply designated them with letters; Meridian Bay (Sinus
Meridiani) was thus feature "a".
Today, features on
Mars are named from a variety of sources. Albedo
features are named for classical mythology. Craters larger than 60 km
are named for deceased scientists and writers and others who have
contributed to the study of Mars. Craters smaller than 60 km are named
for towns and villages of the world with populations of less than
100,000. Large valleys are named for the word "Mars" or "star" in
various languages; small valleys are named for rivers.
Large albedo features retain many of the older names, but are often
updated to reflect new knowledge of the nature of the features. For
example, Nix Olympica (the snows of Olympus) has become Olympus Mons
(Mount Olympus). The surface of
Mars as seen from
Earth is divided
into two kinds of areas, with differing albedo. The paler plains
covered with dust and sand rich in reddish iron oxides were once
thought of as
Martian "continents" and given names like Arabia Terra
(land of Arabia) or
Amazonis Planitia (Amazonian plain). The dark
features were thought to be seas, hence their names
Mare Erythraeum ,
Mare Sirenum and
Aurorae Sinus . The largest dark feature seen from
Syrtis Major Planum . The permanent northern polar ice cap
Planum Boreum , whereas the southern cap is called Planum
Mars's equator is defined by its rotation, but the location of its
Prime Meridian was specified, as was Earth's (at
Greenwich ), by
choice of an arbitrary point; Mädler and Beer selected a line for
their first maps of
Mars in 1830. After the spacecraft Mariner 9
provided extensive imagery of
Mars in 1972, a small crater (later
Airy-0 ), located in the
Sinus Meridiani ("Middle Bay" or
"Meridian Bay"), was chosen for the definition of 0.0° longitude to
coincide with the original selection.
Mars has no oceans and hence no "sea level ", a
zero-elevation surface had to be selected as a reference level; this
is called the areoid of Mars, analogous to the terrestrial geoid .
Zero altitude was defined by the height at which there is 610.5 Pa
(6.105 mbar ) of atmospheric pressure. This pressure corresponds to
the triple point of water, and it is about 0.6% of the sea level
surface pressure on
Earth (0.006 atm). In practice, today this
surface is defined directly from satellite gravity measurements.
Map Of Quadrangles
For mapping purposes, the
United States Geological Survey
United States Geological Survey divides the
Mars into thirty "quadrangles ", each named for a prominent
physiographic feature within that quadrangle. The quadrangles can be
seen and explored via the interactive image map below. 0°N
180°W / 0°N 180°W / 0; -180 0°N 0°W / 0°N
-0°E / 0; -0 90°N 0°W / 90°N -0°E / 90; -0 MC-01
Mare Boreum MC-02 Diacria MC-03 Arcadia MC-04 Mare Acidalium
MC-05 Ismenius Lacus MC-06 Casius MC-07 Cebrenia MC-08 Amazonis
Tharsis MC-10 Lunae Palus MC-11 Oxia Palus MC-12 Arabia
MC-13 Syrtis Major MC-14 Amenthes MC-15 Elysium MC-16 Memnonia
MC-17 Phoenicis MC-18 Coprates MC-19 Margaritifer MC-20 Sabaeus
MC-21 Iapygia MC-22 Tyrrhenum MC-23 Aeolis MC-24 Phaethontis
MC-25 Thaumasia MC-26 Argyre MC-27 Noachis MC-28 Hellas MC-29
Eridania MC-30 Mare Australe The thirty cartographic
quadrangles of Mars, defined by the
United States Geological Survey
United States Geological Survey .
The quadrangles are numbered with the prefix "MC" for "
Click on a quadrangle name link and you will be taken to the
corresponding article. North is at the top; 0°N 180°W / 0°N
180°W / 0; -180 is at the far left on the equator . The map
images were taken by the
Mars Global Surveyor
Mars Global Surveyor .
Bonneville crater and Spirit rover's lander
The dichotomy of
Martian topography is striking: northern plains
flattened by lava flows contrast with the southern highlands, pitted
and cratered by ancient impacts. Research in 2008 has presented
evidence regarding a theory proposed in 1980 postulating that, four
billion years ago, the northern hemisphere of
Mars was struck by an
object one-tenth to two-thirds the size of Earth's
Moon . If
validated, this would make the northern hemisphere of
Mars the site of
an impact crater 10,600 by 8,500 km (6,600 by 5,300 mi) in size, or
roughly the area of Europe, Asia, and Australia combined, surpassing
South Pole–Aitken basin as the largest impact crater in the
Solar System. Fresh asteroid impact on
Mars at 3°20′N
219°23′E / 3.34°N 219.38°E / 3.34; 219.38 . These before
and after images of the same site were taken on the
of March 27 and 28, 2012 respectively (MRO )
Mars is scarred by a number of impact craters: a total of 43,000
craters with a diameter of 5 km (3.1 mi) or greater have been found.
The largest confirmed of these is the Hellas impact basin , a light
albedo feature clearly visible from Earth. Due to the smaller mass of
Mars, the probability of an object colliding with the planet is about
half that of Earth.
Mars is located closer to the asteroid belt , so
it has an increased chance of being struck by materials from that
Mars is more likely to be struck by short-period comets ,
i.e., those that lie within the orbit of Jupiter. In spite of this,
there are far fewer craters on
Mars compared with the Moon, because
the atmosphere of
Mars provides protection against small meteors and
surface modifying processes have erased some craters.
Martian craters can have a morphology that suggests the ground became
wet after the meteor impacted.
Viking 1 image of
Olympus Mons . The volcano and related terrain
are approximately 550 km (340 mi) across. Main article: Volcanology
The shield volcano
Olympus Mons (Mount Olympus) is an extinct volcano
in the vast upland region
Tharsis , which contains several other large
Olympus Mons is roughly three times the height of Mount
Everest , which in comparison stands at just over 8.8 km (5.5 mi). It
is either the tallest or second-tallest mountain in the Solar System,
depending on how it is measured, with various sources giving figures
ranging from about 21 to 27 km (13 to 17 mi) high.
Valles Marineris (
2001 Mars Odyssey )
The large canyon,
Valles Marineris (Latin for "Mariner Valleys", also
known as Agathadaemon in the old canal maps), has a length of 4,000 km
(2,500 mi) and a depth of up to 7 km (4.3 mi). The length of Valles
Marineris is equivalent to the length of Europe and extends across
one-fifth the circumference of Mars. By comparison, the Grand Canyon
Earth is only 446 km (277 mi) long and nearly 2 km (1.2 mi) deep.
Valles Marineris was formed due to the swelling of the
which caused the crust in the area of
Valles Marineris to collapse. In
2012, it was proposed that
Valles Marineris is not just a graben , but
a plate boundary where 150 km (93 mi) of transverse motion has
Mars a planet with possibly a two-tectonic plate
Images from the
Thermal Emission Imaging System (THEMIS) aboard
Mars Odyssey orbiter have revealed seven possible cave
entrances on the flanks of the volcano
Arsia Mons . The caves, named
after loved ones of their discoverers, are collectively known as the
Cave entrances measure from 100 to 252 m (328 to 827
ft) wide and they are estimated to be at least 73 to 96 m (240 to 315
ft) deep. Because light does not reach the floor of most of the caves,
it is possible that they extend much deeper than these lower estimates
and widen below the surface. "Dena" is the only exception; its floor
is visible and was measured to be 130 m (430 ft) deep. The interiors
of these caverns may be protected from micrometeoroids, UV radiation,
solar flares and high energy particles that bombard the planet's
Mars The tenuous atmosphere of Mars
visible on the horizon
Mars lost its magnetosphere 4 billion years ago, possibly because of
numerous asteroid strikes, so the solar wind interacts directly with
Martian ionosphere , lowering the atmospheric density by stripping
away atoms from the outer layer. Both
Mars Global Surveyor
Mars Global Surveyor and Mars
Express have detected ionised atmospheric particles trailing off into
space behind Mars, and this atmospheric loss is being studied by the
MAVEN orbiter. Compared to Earth, the atmosphere of
Mars is quite
Atmospheric pressure on the surface today ranges from a low
of 30 Pa (0.030 kPa ) on
Olympus Mons to over 1,155 Pa (1.155 kPa) in
Hellas Planitia , with a mean pressure at the surface level of 600 Pa
(0.60 kPa). The highest atmospheric density on
Mars is equal to that
found 35 km (22 mi) above Earth's surface. The resulting mean surface
pressure is only 0.6% of that of
Earth (101.3 kPa). The scale height
of the atmosphere is about 10.8 km (6.7 mi), which is higher than
Earth's, 6 km (3.7 mi), because the surface gravity of
Mars is only
about 38% of Earth's, an effect offset by both the lower temperature
and 50% higher average molecular weight of the atmosphere of Mars.
The atmosphere of
Mars consists of about 96% carbon dioxide , 1.93%
argon and 1.89% nitrogen along with traces of oxygen and water. The
atmosphere is quite dusty, containing particulates about 1.5 µm in
diameter which give the
Martian sky a tawny color when seen from the
surface. It may take on a pink hue due to iron oxide particles
suspended in it. Potential sources and sinks of methane (CH
Methane has been detected in the
Martian atmosphere with a
concentration of about 30 ppb ; it occurs in extended plumes, and
the profiles imply that the methane was released from discrete
regions. In northern midsummer, the principal plume contained 19,000
metric tons of methane, with an estimated source strength of 0.6
kilograms per second. The profiles suggest that there may be two
local source regions, the first centered near 30°N 260°W /
30°N 260°W / 30; -260 and the second near 0°N 310°W /
0°N 310°W / 0; -310 . It is estimated that
Mars must produce
270 tonnes per year of methane.
Methane can exist in the
Martian atmosphere for only a limited period
before it is destroyed—estimates of its lifetime range from 0.6–4
years. Its presence despite this short lifetime indicates that an
active source of the gas must be present. Volcanic activity, cometary
impacts, and the presence of methanogenic microbial life forms are
among possible sources.
Methane could be produced by a non-biological
process called serpentinization involving water, carbon dioxide, and
the mineral olivine , which is known to be common on Mars.
Escaping atmosphere on
Mars (carbon , oxygen , and hydrogen ) by MAVEN
The Curiosity rover, which landed on
Mars in August 2012, is able to
make measurements that distinguish between different isotopologues of
methane, but even if the mission is to determine that microscopic
Martian life is the source of the methane, the life forms likely
reside far below the surface, outside of the rover's reach. The first
measurements with the Tunable Laser Spectrometer (TLS) indicated that
there is less than 5 ppb of methane at the landing site at the point
of the measurement. On September 19, 2013,
NASA scientists, from
further measurements by Curiosity, reported no detection of
atmospheric methane with a measured value of
6999180000000000000♠0.18±0.67 ppbv corresponding to an upper limit
of only 1.3 ppbv (95% confidence limit) and, as a result, conclude
that the probability of current methanogenic microbial activity on
Mars is reduced.
Mars Orbiter Mission
Mars Orbiter Mission by
India is searching for methane in the
atmosphere, while the
ExoMars Trace Gas Orbiter , launched in 2016,
would further study the methane as well as its decomposition products,
such as formaldehyde and methanol .
On December 16, 2014,
NASA reported the Curiosity rover detected a
"tenfold spike", likely localized, in the amount of methane in the
Martian atmosphere . Sample measurements taken "a dozen times over 20
months" showed increases in late 2013 and early 2014, averaging "7
parts of methane per billion in the atmosphere." Before and after
that, readings averaged around one-tenth that level.
Ammonia was tentatively detected on
Mars by the
satellite, but with its relatively short lifetime, it is not clear
what produced it. Ammonia is not stable in the
Martian atmosphere and
breaks down after a few hours. One possible source is volcanic
In September 2017,
NASA reported radiation levels on the surface of
Mars were temporarily doubled , and were associated with an
aurora 25-times brighter than any observed earlier, due to a massive,
and unexpected, solar storm in the middle of the month.
In 1994, the European Space Agency's
Mars Express found an
ultraviolet glow coming from "magnetic umbrellas" in the southern
Mars does not have a global magnetic field which guides
charged particles entering the atmosphere.
Mars has multiple
umbrella-shaped magnetic fields mainly in the southern hemisphere,
which are remnants of a global field that decayed billions of years
In late December 2014, NASA's
MAVEN spacecraft detected evidence of
widespread auroras in Mars's northern hemisphere and descended to
approximately 20–30 degrees North latitude of Mars's equator. The
particles causing the aurora penetrated into the
creating auroras below 100 km above the surface, Earth's auroras range
from 100 km to 500 km above the surface. Magnetic fields in the solar
wind drape over Mars, into the atmosphere, and the charged particles
follow the solar wind magnetic field lines into the atmosphere,
causing auroras to occur outside the magnetic umbrellas.
On March 18, 2015,
NASA reported the detection of an aurora that is
not fully understood and an unexplained dust cloud in the atmosphere
Climate of Mars
Dust storm on
Mars November 18,
2012 November 25, 2012 Opportunity and Curiosity rovers are
Of all the planets in the Solar System, the seasons of
Mars are the
most Earth-like, due to the similar tilts of the two planets'
rotational axes. The lengths of the
Martian seasons are about twice
those of Earth's because Mars's greater distance from the
Sun leads to
Martian year being about two
Earth years long.
temperatures vary from lows of about −143 °C (−225 °F) at the
winter polar caps to highs of up to 35 °C (95 °F) in equatorial
summer. The wide range in temperatures is due to the thin atmosphere
which cannot store much solar heat, the low atmospheric pressure, and
the low thermal inertia of
Martian soil. The planet is 1.52 times as
far from the
Sun as Earth, resulting in just 43% of the amount of
Mars had an Earth-like orbit, its seasons would be similar to
Earth's because its axial tilt is similar to Earth's. The
comparatively large eccentricity of the
Martian orbit has a
Mars is near perihelion when it is summer in the
southern hemisphere and winter in the north, and near aphelion when it
is winter in the southern hemisphere and summer in the north. As a
result, the seasons in the southern hemisphere are more extreme and
the seasons in the northern are milder than would otherwise be the
case. The summer temperatures in the south can be up to 30 K (30 °C;
54 °F) warmer than the equivalent summer temperatures in the north.
Mars has the largest dust storms in the Solar System, reaching speeds
of over 100mph. These can vary from a storm over a small area, to
gigantic storms that cover the entire planet. They tend to occur when
Mars is closest to the Sun, and have been shown to increase the global
ORBIT AND ROTATION
Orbit of Mars
Mars is about 230 million
kilometres (143,000,000 mi) from the Sun; its orbital period is 687
(Earth) days, depicted in red. Earth's orbit is in blue.
Mars's average distance from the
Sun is roughly 230 million
kilometres (143,000,000 mi), and its orbital period is 687 (Earth)
days. The solar day (or sol ) on
Mars is only slightly longer than an
Earth day: 24 hours, 39 minutes, and 35.244 seconds. A
is equal to 1.8809
Earth years, or 1 year, 320 days, and 18.2 hours.
The axial tilt of
Mars is 25.19 degrees relative to its orbital plane
, which is similar to the axial tilt of Earth. As a result,
seasons like Earth, though on Mars, they are nearly twice as long
because its orbital period is that much longer. In the present day
epoch, the orientation of the north pole of
Mars is close to the star
Mars passed an aphelion in March 2010 and its perihelion in
March 2011. The next aphelion came in February 2012 and the next
perihelion came in January 2013.
Mars has a relatively pronounced orbital eccentricity of about 0.09;
of the seven other planets in the Solar System, only Mercury has a
larger orbital eccentricity. It is known that in the past,
had a much more circular orbit. At one point, 1.35 million
Mars had an eccentricity of roughly 0.002, much less than that of
Earth today. Mars's cycle of eccentricity is 96,000
compared to Earth's cycle of 100,000 years.
Mars has a much longer
cycle of eccentricity, with a period of 2.2 million
Earth years, and
this overshadows the 96,000-year cycle in the eccentricity graphs. For
the last 35,000 years, the orbit of
Mars has been getting slightly
more eccentric because of the gravitational effects of the other
planets. The closest distance between
Mars will continue to
mildly decrease for the next 25,000 years.
HABITABILITY AND SEARCH FOR LIFE
Colonization of Mars
SEARCH FOR LIFE
Life on Mars and
Viking lander biological experiments
Viking 1 lander's sampling arm scooped up soil samples for tests
Chryse Planitia )
The current understanding of planetary habitability —the ability of
a world to develop environmental conditions favorable to the emergence
of life—favors planets that have liquid water on their surface. Most
often this requires the orbit of a planet to lie within the habitable
zone , which for the
Sun extends from just beyond
Venus to about the
semi-major axis of Mars. During perihelion,
Mars dips inside this
region, but Mars's thin (low-pressure) atmosphere prevents liquid
water from existing over large regions for extended periods. The past
flow of liquid water demonstrates the planet's potential for
habitability. Recent evidence has suggested that any water on the
Martian surface may have been too salty and acidic to support regular
The lack of a magnetosphere and the extremely thin atmosphere of Mars
are a challenge: the planet has little heat transfer across its
surface, poor insulation against bombardment of the solar wind and
insufficient atmospheric pressure to retain water in a liquid form
(water instead sublimes to a gaseous state).
Mars is nearly, or
perhaps totally, geologically dead; the end of volcanic activity has
apparently stopped the recycling of chemicals and minerals between the
surface and interior of the planet. Detection of impact glass
deposits (green spots) at Alga crater , a possible site for preserved
In situ investigations have been performed on
Mars by the Viking
landers , Spirit and Opportunity rovers, Phoenix lander, and Curiosity
rover. Evidence suggests that the planet was once significantly more
habitable than it is today, but whether living organisms ever existed
there remains unknown. The
Viking probes of the mid-1970s carried
experiments designed to detect microorganisms in
Martian soil at their
respective landing sites and had positive results, including a
temporary increase of CO2 production on exposure to water and
nutrients. This sign of life was later disputed by scientists,
resulting in a continuing debate, with
NASA scientist Gilbert Levin
asserting that Viking may have found life. A re-analysis of the Viking
data, in light of modern knowledge of extremophile forms of life, has
suggested that the Viking tests were not sophisticated enough to
detect these forms of life. The tests could even have killed a
(hypothetical) life form. Tests conducted by the Phoenix
have shown that the soil has a alkaline pH and it contains magnesium,
sodium, potassium and chloride. The soil nutrients may be able to
support life, but life would still have to be shielded from the
intense ultraviolet light. A recent analysis of martian meteorite
EETA79001 found 0.6 ppm ClO−
4, 1.4 ppm ClO−
3, and 16 ppm NO−
3, most likely of
Martian origin. The ClO−
3 suggests the presence of other highly oxidizing oxychlorines, such
2 or ClO, produced both by UV oxidation of Cl and X-ray radiolysis of
4. Thus, only highly refractory and/or well-protected (sub-surface)
organics or life forms are likely to survive.
A 2014 analysis of the Phoenix WCL showed that the Ca(ClO
2 in the Phoenix soil has not interacted with liquid water of any
form, perhaps for as long as 600 Myr. If it had, the highly soluble
2 in contact with liquid water would have formed only CaSO
4. This suggests a severely arid environment, with minimal or no
liquid water interaction.
Scientists have proposed that carbonate globules found in meteorite
ALH84001 , which is thought to have originated from Mars, could be
fossilized microbes extant on
Mars when the meteorite was blasted from
Martian surface by a meteor strike some 15 million years ago. This
proposal has been met with skepticism, and an exclusively inorganic
origin for the shapes has been proposed.
Small quantities of methane and formaldehyde detected by Mars
orbiters are both claimed to be possible evidence for life, as these
chemical compounds would quickly break down in the
Alternatively, these compounds may instead be replenished by
volcanic or other geological means, such as serpentinization .
Impact glass , formed by the impact of meteors, which on
preserve signs of life, has been found on the surface of the impact
craters on Mars. Likewise, the glass in impact craters on
have preserved signs of life if life existed at the site.
In May 2017, evidence of the earliest known life on land on
have been found in 3.48-billion-year-old geyserite and other related
mineral deposits (often found around hot springs and geysers )
uncovered in the
Pilbara Craton of
Western Australia . These findings
may be helpful in deciding where best to search for early signs of
life on the planet
Moons of Mars ,
Phobos (moon) , and
HiRISE image of Phobos , showing a series of mostly
parallel grooves and crater chains , with Stickney crater at right
HiRISE image of Deimos (not to scale), showing its
smooth blanket of regolith
Mars has two relatively small natural moons, Phobos (about 22 km (14
mi) in diameter) and Deimos (about 12 km (7.5 mi) in diameter), which
orbit close to the planet.
Asteroid capture is a long-favored theory,
but their origin remains uncertain. Both satellites were discovered
in 1877 by
Asaph Hall ; they are named after the characters Phobos
(panic/fear) and Deimos (terror/dread), who, in
Greek mythology ,
accompanied their father
Ares , god of war, into battle.
Mars was the
Roman counterpart of Ares. In modern Greek , though, the planet
retains its ancient name
Ares (Aris: Άρης).
From the surface of Mars, the motions of Phobos and Deimos appear
different from that of the
Moon . Phobos rises in the west, sets in
the east, and rises again in just 11 hours. Deimos, being only just
outside synchronous orbit – where the orbital period would match the
planet's period of rotation – rises as expected in the east but
slowly. Despite the 30-hour orbit of Deimos, 2.7 days elapse between
its rise and set for an equatorial observer, as it slowly falls behind
the rotation of Mars. Orbits of Phobos and Deimos (to scale)
Because the orbit of Phobos is below synchronous altitude, the tidal
forces from the planet
Mars are gradually lowering its orbit. In about
50 million years, it could either crash into Mars's surface or break
up into a ring structure around the planet.
The origin of the two moons is not well understood. Their low albedo
and carbonaceous chondrite composition have been regarded as similar
to asteroids, supporting the capture theory. The unstable orbit of
Phobos would seem to point towards a relatively recent capture. But
both have circular orbits , near the equator, which is unusual for
captured objects and the required capture dynamics are complex.
Accretion early in the history of
Mars is plausible, but would not
account for a composition resembling asteroids rather than Mars
itself, if that is confirmed.
A third possibility is the involvement of a third body or a type of
impact disruption. More-recent lines of evidence for Phobos having a
highly porous interior, and suggesting a composition containing
mainly phyllosilicates and other minerals known from Mars, point
toward an origin of Phobos from material ejected by an impact on Mars
that reaccreted in
Martian orbit, similar to the prevailing theory
for the origin of Earth's moon. Although the
VNIR spectra of the moons
Mars resemble those of outer-belt asteroids, the thermal infrared
spectra of Phobos are reported to be inconsistent with chondrites of
Mars may have moons smaller than 50 to 100 metres (160 to 330 ft) in
diameter, and a dust ring is predicted to exist between Phobos and
Exploration of Mars Panorama of Gusev crater ,
Spirit rover examined volcanic basalts
Laboratory under parachute during its atmospheric entry at
Dozens of crewless spacecraft , including orbiters , landers , and
rovers , have been sent to
Mars by the Soviet Union , the United
States , Europe , and
India to study the planet's surface, climate,
As of 2016 ,
Mars is host to eight functioning spacecraft : six in
2001 Mars Odyssey ,
Mars Express ,
Mars Reconnaissance Orbiter
Mars Orbiter Mission
Mars Orbiter Mission and
ExoMars Trace Gas Orbiter —and
two on the surface—
Mars Exploration Rover Opportunity and the Mars
Science Laboratory Curiosity . Observations by the
Orbiter have revealed possible flowing water during the warmest months
on Mars. In 2013, NASA's Curiosity rover discovered that Mars's soil
contains between 1.5% and 3% water by mass (albeit attached to other
compounds and thus not freely accessible). The public can request
Mars via the
Mars Reconnaissance Orbiter's
HiWish program .
Mars Science Laboratory , named Curiosity, launched on November
26, 2011, and reached
Mars on August 6, 2012
UTC . It is larger and
more advanced than the
Mars Exploration Rovers, with a movement rate
up to 90 m (300 ft) per hour. Experiments include a laser chemical
sampler that can deduce the make-up of rocks at a distance of 7 m (23
ft). On February 10, 2013, the Curiosity rover obtained the first
deep rock samples ever taken from another planetary body, using its
On September 24, 2014,
Mars Orbiter Mission
Mars Orbiter Mission (MOM), launched by the
Indian Space Research Organisation
Indian Space Research Organisation , reached
MOM on November 5, 2013, with the aim of analyzing the Martian
atmosphere and topography. The
Mars Orbiter Mission
Mars Orbiter Mission used a Hohmann
transfer orbit to escape Earth's gravitational influence and catapult
into a nine-month-long voyage to Mars. The mission is the first
successful Asian interplanetary mission.
European Space Agency
European Space Agency , in collaboration with Roscosmos ,
ExoMars Trace Gas Orbiter and Schiaparelli lander on
March 14, 2016. While the Trace Gas
Orbiter successfully entered Mars
orbit on October 19, 2016, Schiaparelli crashed during its landing
Exploration of Mars § Timeline of
Planned for May 2018 is the launch of NASA's
InSight lander, along
with the twin MarCO CubeSats that will fly by
Mars and provide a
telemetry relay for the landing. The mission is expected to arrive at
Mars in November 2018.
NASA plans to launch its
astrobiology rover in July or August 2020.
European Space Agency
European Space Agency will launch the
ExoMars rover and surface
platform in July 2020.
The United Arab Emirates'
Mars Hope orbiter is planned for launch in
Mars orbit in 2021. The probe will make a global study
Several plans for a human mission to
Mars have been proposed
throughout the 20th century and into the 21st century, but no active
plan has an arrival date sooner than the 2020s.
SpaceX founder Elon
Musk presented a plan in September 2016 to, optimistically, launch
space tourists to
Mars in 2024 at an estimated development cost of
US$10 billion. In October 2016, President
Barack Obama renewed U.S.
policy to pursue the goal of sending humans to
Mars in the 2030s, and
to continue using the
International Space Station
International Space Station as a technology
incubator in that pursuit.
ASTRONOMY ON MARS
Astronomy on Mars See also:
Solar eclipses on Mars
With the presence of various orbiters, landers, and rovers, it is
possible to practice astronomy from Mars. Although Mars's moon Phobos
appears about one-third the angular diameter of the full moon on
Earth, Deimos appears more or less star-like, looking only slightly
Venus does from Earth.
Various phenomena seen from
Earth have also been observed from Mars,
such as meteors and auroras . The apparent sizes of the moons Phobos
and Deimos are sufficiently smaller than that of the Sun; thus, their
partial "eclipses" of the
Sun are best considered transits (see
transit of Deimos and Phobos from Mars). Transits of Mercury and
Venus have been observed from Mars. A transit of
Earth will be seen
Mars on November 10, 2084.
On October 19, 2014,
Comet Siding Spring passed extremely close to
Mars, so close that the coma may have enveloped Mars. Earth
HiRISE , November 2016) Phobos transits the Sun
(Opportunity , March 10, 2004) Tracking sunspots from
Animation of the apparent retrograde motion of
Mars in 2003 as
Because the orbit of
Mars is eccentric, its apparent magnitude at
opposition from the
Sun can range from −3.0 to −1.4. The minimum
brightness is magnitude +1.6 when the planet is in conjunction with
Mars usually appears distinctly yellow, orange, or red; the
actual color of
Mars is closer to butterscotch , and the redness seen
is just dust in the planet's atmosphere.
Spirit rover has
taken pictures of a greenish-brown, mud-colored landscape with
blue-grey rocks and patches of light red sand. When farthest away
from Earth, it is more than seven times farther away than when it is
closest. When least favorably positioned, it can be lost in the Sun's
glare for months at a time. At its most favorable times—at 15- or
17-year intervals, and always between late July and late September—a
lot of surface detail can be seen with a telescope . Especially
noticeable, even at low magnification, are the polar ice caps .
Mars approaches opposition, it begins a period of retrograde
motion , which means it will appear to move backwards in a looping
motion with respect to the background stars. The duration of this
retrograde motion lasts for about 72 days, and
Mars reaches its peak
luminosity in the middle of this motion.
The point at which Mars's geocentric longitude is 180° different
from the Sun's is known as opposition , which is near the time of
closest approach to Earth. The time of opposition can occur as much as
8.5 days away from the closest approach. The distance at close
approach varies between about 54 and about 103 million km due to the
planets' elliptical orbits, which causes comparable variation in
angular size . The last
Mars opposition occurred on May 22, 2016 at a
distance of about 76 million km. The next
Mars opposition occurs on
July 27, 2018 at a distance of about 58 million km. The average time
between the successive oppositions of Mars, its synodic period , is
780 days; but the number of days between the dates of successive
oppositions can range from 764 to 812.
Mars approaches opposition it begins a period of retrograde motion
, which makes it appear to move backwards in a looping motion relative
to the background stars. The duration of this retrograde motion is
about 72 days.
Absolute, Around The Present Time
Mars oppositions from 2003–2018, viewed from above the
Mars made its closest approach to
Earth and maximum apparent
brightness in nearly 60,000 years, 55,758,006 km (0.37271925 AU;
34,646,419 mi), magnitude −2.88, on August 27, 2003 at 9:51:13 UT.
This occurred when
Mars was one day from opposition and about three
days from its perihelion , making it particularly easy to see from
Earth. The last time it came so close is estimated to have been on
September 12, 57,617 BC , the next time being in 2287. This record
approach was only slightly closer than other recent close approaches.
For instance, the minimum distance on August 22, 1924 was
7010557775660904950♠0.37285 AU , and the minimum distance on August
24, 2208 will be 7010557685902182530♠0.37279 AU .
History of Mars observation
History of Mars observation
The history of observations of
Mars is marked by the oppositions of
Mars, when the planet is closest to
Earth and hence is most easily
visible, which occur every couple of years. Even more notable are the
perihelic oppositions of Mars, which occur every 15 or 17 years and
are distinguished because
Mars is close to perihelion, making it even
closer to Earth.
ANCIENT AND MEDIEVAL OBSERVATIONS
The ancient Sumerians believed that
Nergal , the god of war
and plague. During Sumerian times,
Nergal was a minor deity of little
significance, but, during later times, his main cult center was the
Nineveh . In Mesopotamian texts,
Mars is referred to as the
"star of judgement of the fate of the dead". The existence of
a wandering object in the night sky was recorded by the ancient
Egyptian astronomers and, by 1534 BCE, they were familiar with the
retrograde motion of the planet. By the period of the Neo-Babylonian
Empire , the
Babylonian astronomers were making regular records of the
positions of the planets and systematic observations of their
behavior. For Mars, they knew that the planet made 37 synodic periods
, or 42 circuits of the zodiac, every 79 years. They invented
arithmetic methods for making minor corrections to the predicted
positions of the planets.
In the fourth century BCE,
Aristotle noted that
Moon during an occultation , indicating that the planet was
Ptolemy , a Greek living in
Alexandria , attempted to
address the problem of the orbital motion of Mars. Ptolemy's model and
his collective work on astronomy was presented in the multi-volume
Almagest , which became the authoritative treatise on
Western astronomy for the next fourteen centuries. Literature from
ancient China confirms that
Mars was known by Chinese astronomers by
no later than the fourth century BCE. In the fifth century CE, the
Indian astronomical text
Surya Siddhanta estimated the diameter of
Mars. In the
East Asian cultures,
Mars is traditionally referred to
as the "fire star" (火星), based on the Five elements .
During the seventeenth century,
Tycho Brahe measured the diurnal
Johannes Kepler used to make a preliminary
calculation of the relative distance to the planet. When the
telescope became available, the diurnal parallax of
Mars was again
measured in an effort to determine the Sun-
Earth distance. This was
first performed by
Giovanni Domenico Cassini in 1672. The early
parallax measurements were hampered by the quality of the instruments.
The only occultation of
Venus observed was that of October
13, 1590, seen by
Michael Maestlin at
Heidelberg . In 1610,
Galileo Galilei , who was first to see it via telescope.
The first person to draw a map of
Mars that displayed any terrain
features was the Dutch astronomer
Christiaan Huygens .
Mars sketched as
observed by Lowell before 1914 (south on top) Map of
Mars from the
Telescope as seen near the 1999 opposition (north on top)
By the 19th century, the resolution of telescopes reached a level
sufficient for surface features to be identified. A perihelic
Mars occurred on September 5, 1877. In that year, the
Giovanni Schiaparelli used a 22 cm (8.7 in)
Milan to help produce the first detailed map of Mars.
These maps notably contained features he called canali, which were
later shown to be an optical illusion . These canali were supposedly
long, straight lines on the surface of Mars, to which he gave names of
famous rivers on Earth. His term, which means "channels" or "grooves",
was popularly mistranslated in English as "canals".
Influenced by the observations, the orientalist Percival Lowell
founded an observatory which had 30 and 45 cm (12 and 18 in)
telescopes. The observatory was used for the exploration of Mars
during the last good opportunity in 1894 and the following less
favorable oppositions. He published several books on
Mars and life on
the planet, which had a great influence on the public. The canali
were independently found by other astronomers, like Henri Joseph
Louis Thollon in Nice, using one of the largest
telescopes of that time.
The seasonal changes (consisting of the diminishing of the polar caps
and the dark areas formed during
Martian summer) in combination with
the canals led to speculation about life on Mars, and it was a
long-held belief that
Mars contained vast seas and vegetation. The
telescope never reached the resolution required to give proof to any
speculations. As bigger telescopes were used, fewer long, straight
canali were observed. During an observation in 1909 by Flammarion with
an 84 cm (33 in) telescope, irregular patterns were observed, but no
canali were seen.
Even in the 1960s articles were published on
Martian biology, putting
aside explanations other than life for the seasonal changes on Mars.
Detailed scenarios for the metabolism and chemical cycles for a
functional ecosystem have been published.
Exploration of Mars
Once spacecraft visited the planet during NASA's Mariner missions in
the 1960s and 70s, these concepts were radically broken. The results
of the Viking life-detection experiments aided an intermission in
which the hypothesis of a hostile, dead planet was generally accepted.
Mariner 9 and Viking allowed better maps of
Mars to be made using the
data from these missions, and another major leap forward was the Mars
Global Surveyor mission, launched in 1996 and operated until late
2006, that allowed complete, extremely detailed maps of the Martian
topography, magnetic field and surface minerals to be obtained. These
maps are available online; for example, at
Google Mars . Mars
Mars Express continued exploring with new
instruments, and supporting lander missions.
NASA provides two online
Mars Trek , which provides visualizations of the planet using
data from 50 years of exploration, and
Experience Curiosity , which
simulates traveling on
Mars in 3-D with Curiosity.
Mars in culture and
Mars in fiction
Mars is named after the Roman god of war . In different cultures,
Mars represents masculinity and youth. Its symbol , a circle with an
arrow pointing out to the upper right, is used as a symbol for the
The many failures in
Mars exploration probes resulted in a satirical
counter-culture blaming the failures on an Earth-
Triangle ", a "
Mars Curse ", or a "Great Galactic Ghoul" that feeds on
Mars in fiction
The fashionable idea that
Mars was populated by intelligent Martians
exploded in the late 19th century. Schiaparelli\'s "canali"
observations combined with
Percival Lowell 's books on the subject put
forward the standard notion of a planet that was a drying, cooling,
dying world with ancient civilizations constructing irrigation works.
An 1893 soap ad playing on the popular idea that
Many other observations and proclamations by notable personalities
added to what has been termed "
Mars Fever". In 1899, while
investigating atmospheric radio noise using his receivers in his
Colorado Springs lab, inventor
Nikola Tesla observed repetitive
signals that he later surmised might have been radio communications
coming from another planet, possibly Mars. In a 1901 interview Tesla
It was some time afterward when the thought flashed upon my mind that
the disturbances I had observed might be due to an intelligent
control. Although I could not decipher their meaning, it was
impossible for me to think of them as having been entirely accidental.
The feeling is constantly growing on me that I had been the first to
hear the greeting of one planet to another.
Tesla's theories gained support from Lord
Kelvin who, while visiting
the United States in 1902, was reported to have said that he thought
Tesla had picked up
Martian signals being sent to the United States.
Kelvin "emphatically" denied this report shortly before departing
America: "What I really said was that the inhabitants of Mars, if
there are any, were doubtless able to see New York, particularly the
glare of the electricity."
New York Times
New York Times article in 1901,
Edward Charles Pickering ,
director of the
Harvard College Observatory , said that they had
received a telegram from
Lowell Observatory in
Arizona that seemed to
Mars was trying to communicate with Earth.
Early in December 1900, we received from
Lowell Observatory in
Arizona a telegram that a shaft of light had been seen to project from
Mars (the Lowell observatory makes a specialty of Mars) lasting
seventy minutes. I wired these facts to Europe and sent out neostyle
copies through this country. The observer there is a careful, reliable
man and there is no reason to doubt that the light existed. It was
given as from a well-known geographical point on Mars. That was all.
Now the story has gone the world over. In Europe it is stated that I
have been in communication with Mars, and all sorts of exaggerations
have spring up. Whatever the light was, we have no means of knowing.
Whether it had intelligence or not, no one can say. It is absolutely
Pickering later proposed creating a set of mirrors in
intended to signal Martians.
In recent decades, the high-resolution mapping of the surface of
Mars, culminating in
Mars Global Surveyor
Mars Global Surveyor , revealed no artifacts of
habitation by "intelligent" life, but pseudoscientific speculation
about intelligent life on
Mars continues from commentators such as
Richard C. Hoagland . Reminiscent of the canali controversy, these
speculations are based on small scale features perceived in the
spacecraft images, such as "pyramids" and the "
Face on Mars
Face on Mars ".
Carl Sagan wrote:
Mars has become a kind of mythic arena onto which we have projected
our Earthly hopes and fears.
Martian tripod illustration from
the 1906 French edition of
The War of the Worlds by
H. G. Wells
H. G. Wells
The depiction of
Mars in fiction has been stimulated by its dramatic
red color and by nineteenth century scientific speculations that its
surface conditions might support not just life but intelligent life.
Thus originated a large number of science fiction scenarios, among
H. G. Wells
H. G. Wells '
The War of the Worlds , published in 1898, in
which Martians seek to escape their dying planet by invading Earth.
Influential works included
Ray Bradbury 's The
Martian Chronicles ,
in which human explorers accidentally destroy a
Edgar Rice Burroughs '
Barsoom series ,
C. S. Lewis ' novel Out of the
Planet (1938), and a number of
Robert A. Heinlein
Robert A. Heinlein stories
before the mid-sixties.
Jonathan Swift made reference to the moons of Mars, about 150 years
before their actual discovery by
Asaph Hall , detailing reasonably
accurate descriptions of their orbits, in the 19th chapter of his
novel Gulliver\'s Travels .
A comic figure of an intelligent Martian, Marvin the
appeared on television in 1948 as a character in the Looney Tunes
animated cartoons of
Warner Brothers , and has continued as part of
popular culture to the present.
After the Mariner and Viking spacecraft had returned pictures of Mars
as it really is, an apparently lifeless and canal-less world, these
Mars had to be abandoned, and a vogue for accurate,
realist depictions of human colonies on
Mars developed, the best known
of which may be
Kim Stanley Robinson 's
Mars trilogy .
Pseudo-scientific speculations about the
Face on Mars
Face on Mars and other
enigmatic landmarks spotted by space probes have meant that ancient
civilizations continue to be a popular theme in science fiction,
especially in film.
Outline of Mars
Solar System portal
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distance of ≈240,000 kilometres (150,000 mi) during its February
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much smoother and brighter
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* ^ A B C Best-fit ellipsoid
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Olivine is a solid
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Fayalite + Water + Carbonic acid → Serpentine +
Magnetite + Methane, or (in balanced form): 18Mg
4 + 6Fe
4 + 26H
2O + CO
2 → 12Mg
4 + 4Fe
4 + CH
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Find more aboutMARSat's sister projects
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Mars at Curlie (based on
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Google Mars and
Google Mars 3D, interactive maps of the planet
* Geody Mars, mapping