This article presents information and images about viewing astronomical phenomena from the planet Mars. In many cases these are the same or similar to those seen from Earth but sometimes (as with the view of Earth as an evening/morning star) they can be quite different. Note: This article contains special characters. ... Earth (IPA: , often referred to as the Earth, Terra, the World or Planet Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ...

Seasons

Mars has an axial tilt of 25.2°, quite close to the value of 23.45° for Earth, and thus Mars has seasons of spring, summer, autumn, winter as Earth does (if the axial tilt was 0° there would be no seasons). As on Earth, the southern and northern hemispheres have summer and winter at opposing times. Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... Earth (IPA: , often referred to as the Earth, Terra, the World or Planet Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ...

However, the orbit of Mars has significantly greater eccentricity than that of Earth. Therefore the seasons are of unequal length, much more so than on Earth: In astrodynamics, under standard assumptions any orbit must be of conic section shape. ...

In practical terms, this means that summers and winters have different lengths and intensities in the northern and southern hemispheres. Winters in the north are warm and short (because Mars is moving fast near its perihelion), while winters in the south are long and cold (Mars is moving slowly near aphelion). Similarly, summers in the north are long and cool, while summers in the south are short and hot. Therefore extremes of temperature are considerably wider in the southern hemisphere than in the north. This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ...

The seasonal lag on Mars is no more than a couple of days,^[1] due to its lack of large bodies of water and similar factors that would provide a buffering effect. Thus, for temperatures on Mars, spring is approximately the mirror image of summer and autumn is approximately the mirror image of winter, and if Mars had a circular orbit the maximum and minimum temperatures would occur a couple of days after the summer and winter solstices rather than about one month after as on Earth. The only difference between spring temperatures and summer temperatures is due to the relatively high eccentricity of Mars's orbit: in northern spring Mars is farther from the Sun than during northern summer, and therefore by coincidence spring is slightly cooler than summer and autumn is slightly warmer than winter. However, in the southern hemisphere the opposite is true. Seasonal lag is the phenomenon whereby the date of maximum average air temperature at a geographical location on a planet is delayed until some time after the date of maximum insolation. ... This article or section needs a complete rewrite for the reasons listed on the talk page. ...

Of course, the temperature variations between spring and summer are much less than the very sharp variations that occur within a single Martian sol (solar day). On a daily basis, temperature peak at local solar noon and reach a minimum at local midnight. This is similar to the effect in Earth's deserts, only much more pronounced.

An illustration of what Mars may have looked like during an ice age about 400,000 years ago caused by a large axial tilt

It is interesting to note that the axial tilt and eccentricity of Earth (or Mars) are by no means fixed, but rather vary due to gravitational perturbations from other planets in the solar system on a timescale of tens of thousands or hundreds of thousands of years. Thus, for example Earth's eccentricity of about 1% regularly fluctuates and can increase up to 6%, and at some point in the distant future the Earth will also have to deal with the calendrical implications of seasons of widely differing length (not to mention the major climate disruptions that go along with it). Credit: NASA/JPL/Brown University [1] An illustration of what Mars might have looked like during an ice age between 2. ... Credit: NASA/JPL/Brown University [1] An illustration of what Mars might have looked like during an ice age between 2. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... Major features of the Solar System (not to scale): The Sun, the eight planets, the asteroid belt containing the dwarf planet Ceres, outermost there is the dwarf planet Pluto (the dwarf planet Eris not shown), and a comet. ...

Aside from the eccentricity, the Earth's axial tilt can also vary from 21.5° to 24.5°, and the length of this "obliquity cycle" is 41000 years. These and other similar cyclical changes are thought to be responsible for ice ages (see Milankovitch cycles). By contrast, the obliquity cycle for Mars is much more extreme: from 15° to 35° over a 124,000-year cycle. Some recent studies even suggest that over tens of millions of years, the swing may be as much as 0° to 60°.^[2] Earth's large Moon apparently plays an important role in keeping Earth's axial tilt within reasonable bounds; Mars has no such stabilizing influence and its axial tilt can vary more dddddd Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... Variations in CO2, temperature and dust from the Vostok ice core over the last 400 000 years For the animated movie, see Ice Age (movie). ... Milankovitch cycles are the collective effect of changes in the Earths movements upon its climate, named after Serbian geophysicist Milutin Milanković. The eccentricity, axial tilt, and precession of the Earths orbit vary in several patterns, resulting in 100,000 year ice age cycles of the Quaternary glaciation over...

The color of the sky

Mars's sky turned violet by water ice clouds

Mars sky at local noon, as imaged by Mars Pathfinder

Mars sky at sunset, as imaged by Mars Pathfinder

Close-up of Mars sky at sunset, showing more color variation, as imaged by Mars Pathfinder

Courtesy: NASA/JPL The usually pinkish-red color of Marss sky turns a violet color on occasion, due to the presence of water ice clouds with very small ice particles. ... Courtesy: NASA/JPL The usually pinkish-red color of Marss sky turns a violet color on occasion, due to the presence of water ice clouds with very small ice particles. ... Download high resolution version (982x236, 13 KB)Courtesy: NASA/JPL-Caltech The Martian sky at noon is yellow-brown, which contrasts with its pinkish-red color at sunset. ... Download high resolution version (982x236, 13 KB)Courtesy: NASA/JPL-Caltech The Martian sky at noon is yellow-brown, which contrasts with its pinkish-red color at sunset. ... The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II rocket, just a month after the Mars Global Surveyor was launched. ... Download high resolution version (2853x699, 47 KB)Courtesy: NASA/JPL-Caltech Sunset on Mars, as imaged by Mars Pathfinder. ... Download high resolution version (2853x699, 47 KB)Courtesy: NASA/JPL-Caltech Sunset on Mars, as imaged by Mars Pathfinder. ... The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II rocket, just a month after the Mars Global Surveyor was launched. ... Courtesy: NASA/JPL-Caltech Sunset on Mars as imaged by Mars Pathfinder This is a close-up of the sunset on Sol 24 as seen by the Imager for Mars Pathfinder. ... Courtesy: NASA/JPL-Caltech Sunset on Mars as imaged by Mars Pathfinder This is a close-up of the sunset on Sol 24 as seen by the Imager for Mars Pathfinder. ... The Mars Pathfinder was launched on December 4, 1996 by NASA aboard a Delta II rocket, just a month after the Mars Global Surveyor was launched. ...

Around sunset and sunrise the Martian sky is pinkish-red in color, but in the vicinity of the setting sun it is blue. This is the exact replica of the situation on Earth. However, during the day the sky is a yellow-brown "butterscotch" color.^[3]

On Mars Rayleigh scattering is usually a very small effect. It is believed that the color of the sky is caused by the presence of 1% by volume of magnetite in the dust particles. Rayleigh scattering causing a reddened sky at sunset Rayleigh scattering (named after Lord Rayleigh) is the scattering of light, or other electromagnetic radiation, by particles much smaller than the wavelength of the light. ... // Headline text Magnetite is a ferrimagnetic mineral form of iron(II,III) oxide, with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. ...

Twilight lasts a long time after the Sun has set and before it rises, because of all the dust in Mars's atmosphere.

At times, the Martian sky takes on a violet color, due to scattering of light by very small water ice particles in clouds.^[4]

Generating accurate true-color images of Mars's surface is surprisingly complicated.^[5] There is much variation in the color of the sky as reproduced in published images; many of those images however are using filters to maximize the science value and are not trying to show true color. Nevertheless, for many years, the sky on Mars was thought to be more pinkish than it now is believed to be.

Astronomical phenomena

Earth and Moon

Earth and Moon from Mars, imaged by Mars Global Surveyor on May 8, 2003 13:00 UTC. South America is visible.

Earth as morningstar imaged by MER Spirit on March 7, 2004

As seen from Mars, the Earth is an inner planet like Venus (a "morning star" or "evening star"). The Earth and Moon appear starlike to the naked eye, but observers with telescopes would see them as crescents, with some detail visible. Download high resolution version (961x961, 17 KB)Courtesy NASA/JPL/Malin Space Science Systems [1] [2] Image of Earth and Moon, taken by the Mars Orbiter Camera of Mars Global Surveyor on May 8, 2003 at 12:59:58 UTC. South America is visible. ... Download high resolution version (961x961, 17 KB)Courtesy NASA/JPL/Malin Space Science Systems [1] [2] Image of Earth and Moon, taken by the Mars Orbiter Camera of Mars Global Surveyor on May 8, 2003 at 12:59:58 UTC. South America is visible. ... Artists conception of Mars Global Surveyor (NASA) The Mars Global Surveyor (MGS) is a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. ... May 8 is the 128th day of the year in the Gregorian Calendar (129th in leap years). ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... ... Image File history File links Download high-resolution version (1194x1007, 53 KB) http://photojournal. ... Image File history File links Download high-resolution version (1194x1007, 53 KB) http://photojournal. ... The mission patch for Spirit, featuring Marvin the Martian. ... March 7 is the 66th day of the year in the Gregorian Calendar (67th in leap years). ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

An observer on Mars would be able to see the Moon orbiting around the Earth, and this would easily be visible to the naked eye. By contrast, observers on Earth cannot see any other planet's satellites with the naked eye, and it was not until soon after the invention of the telescope that the first such satellites were discovered (Jupiter's Galilean moons). The naked eye is a figure of speech referring to human visual perception that is unaided by enhancing equipment, such as a telescope or binoculars. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ... Jupiters 4 Galilean moons, in a composite image comparing their sizes and the size of Jupiter (Great Red Spot visible). ...

At maximum angular separation, the Earth and Moon would be easily distinguished as a double planet, but about one week later they would merge into a single point of light (to the naked eye), and then about a week after that, the Moon would reach maximum angular separation on the opposite side. The maximum angular separation of the Earth and Moon varies considerably according to the relative distance between the Earth and Mars: it is about 17′ when Earth is closest to Mars (near inferior conjunction) but only about 3.5′ when the Earth is farthest from Mars (near superior conjunction). For comparison, the apparent diameter of the Moon from Earth is 31′. Conjunction is a term used in positional astronomy and astrology. ... Conjunction is a term used in positional astronomy and astrology. ...

The minimum angular separation would be less than 1′, and occasionally the Moon would be seen to transit in front of or pass behind (be occulted by) the Earth. The former case would correspond to a lunar occultation of Mars as seen from Earth, and because the Moon's albedo is considerably less than that of the Earth, a dip in overall brightness would occur, although this would be too small to be noticeable by casual naked eye observers because the size of the Moon is much smaller than that of the Earth and it would cover only a small fraction of the Earth's disk. Deimos transits the Sun, as seen by Mars Rover Opportunity on March 4, 2004 The word transit has two meanings in astronomy: A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at... In this July, 1997 still frame captured from video, the bright star Aldebaran has just reappeared on the dark limb of the waning crescent moon in this predawn occultation. ... Albedo is a ratio of scattered to incident electromagnetic radiation power. ...

Mars Global Surveyor imaged the Earth and Moon on May 8, 2003 13:00 UTC, very close to maximum angular elongation from the Sun and at a distance of 0.930 AU from Mars. The apparent magnitudes were given as -2.5 and +0.9.^[6] At different times the actual magnitudes will vary considerably depending on distance and the phases of the Earth and Moon. Artists conception of Mars Global Surveyor (NASA) The Mars Global Surveyor (MGS) is a US spacecraft developed by NASA and the Jet Propulsion Laboratory and launched November 1996. ... May 8 is the 128th day of the year in the Gregorian Calendar (129th in leap years). ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... This diagram shows the elongations (or angle) of the Earths position from the Sun. ... The Sun is the star of our solar system. ...

From one day to the next, the view of the Moon would change very differently for an observer on Mars than for an observer on Earth. The phase of the Moon as seen from Mars would not change much from day to day; it would match the phase of the Earth, and would only gradually change as both Earth and Moon move in their orbits around the Sun. On the other hand, an observer on Mars would see the Moon rotate, with the same period as its orbital period, and would see far side features that can never be seen from Earth. It has been suggested that New moon be merged into this article or section. ...

Since Earth is an inner planet, observers on Mars can occasionally view transits of Earth across the Sun. The next one will take place in 2084. Of course, they can also view transits of Mercury and transits of Venus as well. Earth and Moon transiting the Sun in 2084, as seen from Mars Earth and Moon from Mars, as imaged by Mars Global Surveyor A transit of Earth across the Sun as seen from Mars takes place when the planet Earth passes directly between the Sun and Mars, obscuring a small... The Sun is the star of our solar system. ... (Redirected from 2084) (20th century - 21st century - 22nd century - other centuries) Definition In calendars based on the Christian Era or Common Era, such as the Gregorian calendar, the 21st century is the current century, as of this writing, lasting from 2000-2099. ... A transit of Mercury across the Sun as seen from Mars takes place when the planet Mercury passes directly between the Sun and Mars, obscuring a small part of the Suns disc for an observer on Mars. ... A transit of Venus across the Sun as seen from Mars takes place when the planet Venus passes directly between the Sun and Mars, obscuring a small part of the Suns disc for an observer on Mars. ...

Phobos and Deimos

Phobos eclipses the Sun imaged by MER

The moon Phobos appears about one third the angular diameter that the full Moon appears from Earth; on the other hand, Deimos appears more or less starlike with a disk barely discernible if at all. Phobos orbits so fast that it rises in the west and sets in the east; Deimos on the other hand rises in the east and sets in the west, but orbits only a few hours slower than a Martian sol, so it takes about two and a half days between rising and setting. Image File history File links PIA05553. ... Image File history File links PIA05553. ... Phobos transits the Sun, as seen by Mars Rover Opportunity on March 10, 2004 A transit of Phobos across the Sun as seen from Mars takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Suns... Artists Concept of Rover on Mars (credit: Maas Digital LLC) NASAs 2003 Mars Exploration Rover (MER) Mission is an ongoing unmanned Mars exploration mission, commenced in 2003, that sent two robotic rovers Spirit and Opportunity to explore the Martian surface and geology. ... Phobos (IPA , Greek Φόβος: Fright), is the larger and innermost of Mars two moons, and is named after Phobos, son of Ares (Mars) from Greek Mythology. ... Adjective lunar Bulk silicate composition (estimated wt%) SiO2 44. ... Deimos (IPA or ; Greek Δείμος: Dread), is the smaller and outermost of Mars’ two moons, named after Deimos from Greek Mythology. ...

The maximum brightness of Phobos at "full moon" is about magnitude -9 or -10, while for Deimos it is about -5.^[7] By comparison, the full Moon as seen from Earth is considerably brighter at magnitude -12.7. Phobos is still bright enough to cast shadows; Deimos is only slightly brighter than Venus is from Earth. Of course, just like Earth's Moon, both Phobos and Deimos are considerably fainter at non-full phases. Unlike Earth's Moon, Phobos's phases and angular diameter visibly change from hour to hour; Deimos is too small for its phases to be visible with the naked eye. Adjective lunar Bulk silicate composition (estimated wt%) SiO2 44. ... (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ...

Both Phobos and Deimos have low-inclination equatorial orbits and orbit fairly close to Mars. As a result, Phobos is not visible from latitudes north of 70.4°N or south of 70.4°S; Deimos is not visible from latitudes north of 82.7°N or south of 82.7°S. Observers at high latitudes (less than 70.4°) would see a noticeably smaller angular diameter for Phobos because they are farther away from it. Similarly, equatorial observers of Phobos would see a noticeably smaller angular diameter for Phobos when it is rising and setting, compared to when it is overhead.

Observers on Mars can view transits of Phobos and transits of Deimos across the Sun. The transits of Phobos could also be called partial eclipses of the Sun by Phobos, since the angular diameter of Phobos is up to half the angular diameter of the Sun. However, in the case of Deimos the term "transit" is appropriate, since it appears as a small dot on the Sun's disk. Phobos transits the Sun, as seen by Mars Rover Opportunity on March 10, 2004 A transit of Phobos across the Sun as seen from Mars takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Suns... Deimos transits the Sun, as seen by Mars Rover Opportunity on March 4, 2004 A transit of Deimos across the Sun as seen from Mars takes place when Deimos passes directly between the Sun and a point on the surface of Mars, obscuring a small part of the Suns... The Sun is the star of our solar system. ... The French 1999 eclipse An eclipse (Greek verb: ekleipô, to vanish, though it derives from the prefix ex-, away from, and Greek leipein, to leave) is an astronomical event that occurs when one celestial object moves into the shadow of another. ...

Since Phobos orbits in a low-inclination equatorial orbit, there is a seasonal variation in the latitude of the position of Phobos's shadow projected onto the Martian surface, cycling from far north to far south and back again. At any given fixed geographical location on Mars, there are two intervals per Martian year when the shadow is passing through its latitude and about half a dozen transits of Phobos can be observed at that geographical location over a couple of weeks during each such interval. The situation is similar for Deimos, except only zero or one transits occur during such an interval. The satellite Phobos orbits very close to Mars and casts a penumbral shadow on the Martian surface. ...

It is easy to see that the shadow always falls on the "winter hemisphere", except when it crosses the equator during the vernal equinox and the autumnal equinox. Thus transits of Phobos and Deimos happen during Martian autumn and winter in the northern hemisphere and the southern hemisphere. Close to the equator they tend to happen around the autumnal equinox and the vernal equinox; farther from the equator they tend to happen closer to the winter solstice. In either case, the two intervals when transits can take place occur more or less symmetrically before and after the winter solstice (however, the large eccentricity of Mars's orbit prevents true symmetry). Illumination of Earth by Sun on the day of equinox The vernal equinox (or spring equinox) marks the beginning of astronomical spring. ... Illumination of Earth by Sun on the day of equinox The autumnal equinox (or fall equinox) marks the beginning of astronomical autumn. ... This article or section needs a complete rewrite for the reasons listed on the talk page. ...

The rapid motion of Mars's moons creates the possibility of using them for celestial navigation. In particular, their position among the stars could be used as a basis for telling global time accurately, and combined with knowledge of local time from observing the Sun this could be used to determine the longitude of the observer's position. On Earth, this was historically known as the "lunar distances" method of determining longitude, but was less practical because of the Moon's much slower motion and was superseded by John Harrison's invention of a sufficiently accurate chronometer. An additional complication of the lunar distances method on Earth was the fact that the Moon's considerable mass and its greater distance from Earth makes determining its orbit a three-body problem beyond the capabilities of accurate computation by early astronomers. Celestial Navigation is the 15th episode of The West Wing. ... Longitude, sometimes denoted by the Greek letter λ, describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. ... John Harrison John Harrison (March 24, 1693–March 24, 1776) was an English clockmaker, who designed and built the worlds first successful chronometer (maritime clock), one whose accuracy was great enough to allow the determination of longitude over long distances. ... The n-body problem is the problem of finding, given the initial positions, masses, and velocities of n bodies, their subsequent motions as determined by classical mechanics, i. ...

Observers on Mars can also view lunar eclipses of Phobos and Deimos. Phobos spends about an hour in Mars's shadow; for Deimos it is about two hours. Surprisingly, despite its orbit being nearly in the plane of Mars's equator and despite its very close distance to Mars, there are some occasions when Phobos escapes being eclipsed. An eclipse refers to the phenomenon of one body passing into the shadow cast by another body. ...

Phobos and Deimos both have synchronous rotation, which means that they have a "far side" that observers on the surface of Mars can't see. The phenomenon of libration occurs for Phobos as it does for Earth's Moon, despite the low inclination and eccentricity of Phobos's orbit.^[8][9] Due to the effect of librations and the parallax due to the close distance of Phobos, by observing at high and low latitudes and observing as Phobos is rising and setting, the overall total coverage of Phobos's surface that is visible at one time or another from one location or another on Mars's surface is considerably higher than 50%. In astronomy, synchronous rotation is a planetological term describing a body orbiting another, where the orbiting body takes as long to rotate on its axis as it does to make one orbit; and therefore always keeps the same hemisphere pointed at the body it is orbiting. ... The animation shows a set of simulated views of the Moon over one month, like a picture taken at the same time each day. ... Adjective lunar Bulk silicate composition (estimated wt%) SiO2 44. ... This article or section does not cite its references or sources. ...

The large Stickney crater is visible along one edge of the face of Phobos. It is easily visible with the naked eye from the surface of Mars. Stickney crater (at left), with radiating grooves Stickney at top in sunlight, imaged by Mars Global Surveyor Stickney crater is the largest crater on Phobos, which is a satellite of Mars. ...

Meteors and meteor showers

First meteor photographed from Mars, March 7, 2004 by Spirit rover

Since Mars has an atmosphere that is relatively transparent at optical wavelengths (just like Earth, albeit much thinner), meteors will occasionally be seen. Meteor showers on Earth occur when the Earth intersects the orbit of a comet, and likewise, Mars also has meteor showers, although these are different from the ones on Earth. Image File history File links Download high resolution version (1174x1041, 397 KB)This is an image of what is now believed to be the first meteor photographed on Mars. ... Image File history File links Download high resolution version (1174x1041, 397 KB)This is an image of what is now believed to be the first meteor photographed on Mars. ... March 7 is the 66th day of the year in the Gregorian Calendar (67th in leap years). ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Spirit (official designation: MER-A) is the first of the two Mars Exploration Rover Missions. ... Photo of a burst of meteors with extended exposure time A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ... Leonid Meteor Shower // A meteor shower, also known as a meteor storm, is a celestial event where a large number of meteors are seen within a very short period of time. ... A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail â€” both primarily from the effects of solar radiation upon the comets nucleus, which itself is a minor body composed of rock, dust...

The first meteor photographed on Mars (on March 7, 2004 by the Spirit rover) is now believed to have been part of a meteor shower whose parent body is comet 114P/Wiseman-Skiff. Because the radiant is in the constellation Cepheus, this meteor shower could be dubbed the Martian "Cepheids". March 7 is the 66th day of the year in the Gregorian Calendar (67th in leap years). ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... Spirit (official designation: MER-A) is the first of the two Mars Exploration Rover Missions. ... 114P/Wiseman-Skiff is a periodic comet in our solar system. ... Cepheus (IPA: ) is a northern constellation named after King Cepheus in Greek mythology, and is considered to represent a king. ...

It is predicted that there will be an intense Cepheid meteor shower on Mars on December 20, 2007.^[10] December 20 is the 354th day of the year (355th in leap years) in the Gregorian calendar. ... 2007 (MMVII) will be a common year starting on Monday of the Gregorian calendar. ...

As on Earth, when a meteor is large enough to actually land (without burning up completely in the atmosphere), it becomes a meteorite. The first known meteorite discovered on Mars (and the first known meteorite anywhere other than Earth) was Heat Shield Rock. Willamette Meteorite A meteorite is an extraterrestrial body that survives its impact with the Earths surface without being destroyed. ... Heat shield, with Heat Shield Rock just above and to the left in the background (click to enlarge) Heat Shield Rock is a basketball-sized iron-nickel meteorite found on Mars by the Mars rover Opportunity in January 2005. ...

Auroras

Auroras occur on Mars, but they do not occur at the poles as on Earth, because Mars has no planetwide magnetic field. Rather, they occur near magnetic anomalies in Mars's crust, which are remnants from earlier days when Mars did have a magnetic field. Martian auroras are a distinct kind not seen elsewhere in the solar system.^[11] They would probably also be invisible to the human eye, being largely ultraviolet phenomena.^[12] Aurora borealis Aurora borealis The aurora is a bright glow observed in the night sky, usually in the polar zone. ... Earth cutaway from core to exosphere. ...

Celestial poles and ecliptic

The orientation of Mars's axis is such that its north celestial pole is in Cygnus at R.A. 21h 10m 42s Decl. 52° 53.0' (or more precisely, 317.67669 +52.88378), near the 6th-magnitude star BD +52 2880 (also known as HR 8106, HD 201834, or SAO 33185), which in turn is at R.A. 21h 10min 15.6sec Decl. +53° 33' 48". The two celestial poles are the imaginary points where the Earths spin axis intersects the imaginary rotating sphere of gigantic radius, called the celestial sphere. ... Cygnus (Latin for swan) is a northern constellation. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ...

This position is about halfway between Deneb and Alpha Cephei, less than 10° from the former. This means that in nearly all of the northern hemisphere except areas close to the equator, Deneb never sets, but permanently circles the north pole. The orientation of Deneb would make a useful clock hand for telling sidereal time. Deneb (α Cyg / α Cygni / Alpha Cygni) is the brightest star in the constellation Cygnus and one of the brightest stars in the night sky, with apparent magnitude 1. ... Sidereal time is time measured by the apparent diurnal motion of the vernal equinox, which is very close to, but not identical with, the motion of stars. ...

Mars's north celestial pole is also only a few degrees away from the galactic plane. Thus the Milky Way, especially rich in the area of Cygnus, is always visible. The galactic plane is the plane in which the majority of a flattened galaxys mass lies. ... The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias), sometimes referred to simply as the Galaxy), is a barred spiral galaxy of the Local Group. ...

The south celestial pole is correspondingly found at 9h 10m 42s and -52° 53.0', which is a couple of degrees from the 2.5 magnitude star Kappa Velorum (which is at 9h 22m 06.85s -55° 00.6'), which could therefore be considered the southern polar star. The star Canopus, second brightest in the sky, is a circumpolar star for most southern latitudes, except close to the equator. Kappa Velorum (κ Vel / κ Velorum) is a binary star in the constellation Vela. ... Canopus (α Car / α Carinae / Alpha Carinae) is the brightest star in the southern constellation of Carina, and the second brightest star in the sky, with a visual magnitude of −0. ...

The zodiac constellations of Mars's ecliptic are almost the same as those of Earth — after all, the two ecliptic planes only have a mutual inclination of 1.85° — but on Mars, the Sun spends 6 days in the constellation Cetus, leaving and re-entering Pisces as it does so. The equinoxes and solstices are different as well: for the northern hemisphere, vernal equinox is in Ophiuchus, summer solstice is at the border of Aquarius and Pisces, autumnal equinox is in Taurus, and winter solstice is in Virgo. This article is about the astrological and astronomical concept of the zodiac. ... The plane of the ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... This article or section does not cite its references or sources. ... Cetus (a name from Greek mythology, referring to a Whale or Sea monster, see Ceto) is a constellation of the southern sky, in the region known as the Water, near other watery constellations like Aquarius, Pisces, and Eridanus. ... For the astrological sign, see Pisces (astrology). ... Illumination of Earth by Sun on the day of equinox The vernal equinox (or spring equinox) marks the beginning of astronomical spring. ... Ophiuchus is one of the 88 constellations, and was also one of the 48 listed by Ptolemy. ... Illumination of Earth by the sun on the northern hemisphere summer solstice The summer solstice is an astronomical term regarding the position of the sun in relation to the celestial equator. ... Aquarius (Latin for the Water-bearer or Cup-bearer, symbol , Unicode â™’) is the first sign of the zodiac, situated between Capricornus and Pisces. ... For the astrological sign, see Pisces (astrology). ... Illumination of Earth by Sun on the day of equinox The autumnal equinox (or fall equinox) marks the beginning of astronomical autumn. ... For other uses of the word Taurus see Taurus. ... This article or section needs a complete rewrite for the reasons listed on the talk page. ... See VIRGO (physics) for a French-Italian project in physics. ...

As on Earth, precession will cause the solstices and equinoxes to cycle through the zodiac constellations over thousands and tens of thousands of years. Precession refers to a change in the direction of the axis of a rotating object. ...

Long-term variations

As on Earth, the effect of precession causes the north and south celestial poles to move in a very large circle, but on Mars the cycle is 175,000 Earth years rather than 26,000 years as on Earth. Precession refers to a change in the direction of the axis of a rotating object. ...

As on Earth, there is a second form of precession: the point of perihelion in Mars's orbit changes slowly, causing the anomalistic year to differ from the sidereal year. However, on Mars, this cycle is 51,000 years rather than 21,000 years as on Earth. This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... The sidereal year is the time for the Sun to return to the same position in respect to the stars of the celestial sphere. ...

As on Earth, the period of rotation of Mars (the length of its day) is slowing down. However, this effect is three orders of magnitude smaller than on Earth because the gravitational effect of Phobos is negligible and the effect is mainly due to the Sun.^[13] On Earth, the gravitational influence of the Moon has a much greater effect. Eventually, in the far future, the length of a day on Earth will equal and then exceed the length of a day on Mars.

As on Earth, Mars experiences Milankovitch cycles that cause its axial tilt (obliquity) and orbital eccentricity to vary over long periods of time, which has long term effects on its climate. The variation of Mars's axial tilt is much larger than for Earth because it lacks the stabilizing influence of a large moon like Earth's moon. Mars has a 124,000-year obliquity cycle compared to 41,000 years for Earth. Milankovitch cycles are the collective effect of changes in the Earths movements upon its climate, named after Serbian geophysicist Milutin Milanković. The eccentricity, axial tilt, and precession of the Earths orbit vary in several patterns, resulting in 100,000 year ice age cycles of the Quaternary glaciation over... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... In astrodynamics, under standard assumptions any orbit must be of conic section shape. ...

See also

• Timekeeping on Mars
• Skies of other planets

• Transit of Phobos from Mars
• Transit of Deimos from Mars

• Transit of Mercury from Mars
• Transit of Venus from Mars
• Transit of Earth from Mars

Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars. ... The sky of a world refers to the view of the heavens from its surface. ... Phobos transits the Sun, as seen by Mars Rover Opportunity on March 10, 2004 A transit of Phobos across the Sun as seen from Mars takes place when Phobos passes directly between the Sun and a point on the surface of Mars, obscuring a large part of the Suns... Deimos transits the Sun, as seen by Mars Rover Opportunity on March 4, 2004 A transit of Deimos across the Sun as seen from Mars takes place when Deimos passes directly between the Sun and a point on the surface of Mars, obscuring a small part of the Suns... A transit of Mercury across the Sun as seen from Mars takes place when the planet Mercury passes directly between the Sun and Mars, obscuring a small part of the Suns disc for an observer on Mars. ... A transit of Venus across the Sun as seen from Mars takes place when the planet Venus passes directly between the Sun and Mars, obscuring a small part of the Suns disc for an observer on Mars. ... Earth and Moon transiting the Sun in 2084, as seen from Mars Earth and Moon from Mars, as imaged by Mars Global Surveyor A transit of Earth across the Sun as seen from Mars takes place when the planet Earth passes directly between the Sun and Mars, obscuring a small...

References

1. ^ http://pds-atmospheres.nmsu.edu/education_and_outreach/encyclopedia/radiative_time_constant.htm
2. ^ http://www.spacedaily.com/news/mars-water-science-00d.html
3. ^ http://humbabe.arc.nasa.gov/mgcm/faq/sky.html
4. ^ http://starryskies.com/The_sky/events/mars/opposition08.html
5. ^ http://www.badastronomy.com/bad/misc/hoagland/mars_colors.html
6. ^ http://www.msss.com/mars_images/moc/2003/05/22/
7. ^ http://www.arm.ac.uk/~aac/mars/Information.html
8. ^ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1990A%26A...233..235B
9. ^ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1991BAICz..42..271P
10. ^ http://www.space.com/scienceastronomy/050601_mars_meteor.html
11. ^ Graham, Sarah. "Martian Aurora Is One of a Kind", Scientific American, June 09, 2005. Retrieved on 2006-10-24.
12. ^ http://www.physorg.com/news8987.html
13. ^ http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?1988BAICz..39..168B

2006 (MMVI) is a common year starting on Sunday of the Gregorian calendar. ... October 24 is the 297th day of the year (298th in leap years) in the Gregorian Calendar, with 68 days remaining. ...

External links

• Mars fact sheet
• Analemma on Mars