This is one of the first images taken by NASA's Curiosity rover, which landed on Mars the evening of Aug. 5 PDT (morning of Aug. 6 EDT). Image credit: NASA/JPL-Caltech
› Full image and caption | › Curiosity latest images
August 05, 2012
PASADENA, Calif. -- NASA's most advanced Mars rover Curiosity has landed on the Red Planet. The one-ton rover, hanging by ropes from a rocket backpack, touched down onto Mars Sunday to end a 36-week flight and begin a two-year investigation.
Guy Webster / D.C. Agle 818-354-6278 / 818-393-9011
Curiosity Has Landed
CHECK OUT ASTROPHOTOGRAPHER EXTRAORDINAIRE CHRISTOPHER GO IN THE PHILIPPINES MARS 2012 WEBSITE PAGE AT:
THE ASTRONOMY PICTURE OF THE DAY FOR 2010 February 5
Credit & Copyright: Jean-Luc Dauvergne, Francois Colas, IMCCE/S2P, Obs. Midi-Pyrénées
Explanation: It's spring for the northern hemisphere of Mars and spring on Mars usually means dust storms. So the dramatic brown swath of dust (top) marking the otherwise white north polar cap in this picture of the Red Planet is not really surprising. Taking advantage of the good views of Mars currently possible near opposition and its closest approach to planet Earth in 2010, this sharp image shows the evolving dust storm extending from the large dark region known as Mare Acidalium below the polar cap. It was recorded on 2010 February 2nd with the 1 meter telescope at Pic Du Midi, a mountain top observatory in the French Pyrenees.
by Nancy Atkinson on November 22, 2011 From UniverseToday.com
A region on the rim of Endeavour Crater on Mars that has been named 'Turkey Haven,' Credit: NASA/JPL, colorization by Stu Atkinson.
What does a Mars Rover do for the Thanksgiving holiday? While one rover will be sitting on the launchpad, preparing to head to the Red Planet (MSL/ Curiosity) the Opportunity rover has now trekked to an enticing outcrop near the summit of Cape York on the rim of Endeavour Crater. This summit or ridge has been named “Turkey Haven” by the MER science team, as this is where Oppy will conduct scientific studies over the four-day-long US holiday. The image above was taken a few days ago, showing the Turkey Haven ridge. Our pal Stu Atkinson has provided a beautiful color rendering, and you can see all the rocks that the rover will be looking at more closely with its suite of instruments and cameras. You can see more images of this area, including 3-D versions on Stu’s site, Road to Endeavour.
Oppy is now sitting among these rocks studying the outcrop region seen on the left.
And there’s other enticing regions ahead to study as well.
An usual dagger-shaped feature along the rim of Endeavour Crater, as seen by the HiRISE camera on the Mars Reconnaissance Orbiter. Credit: NASA/JPL
A dagger-shaped gorge or geological fault, as seen from above by the Mars Reconnaissance Orbiter may well be a future destination, but likely after Oppy finds another haven – a winter haven – a good place and location for soaking up as much sunshine as possible for the upcoming long winter on Mars.
The rock outrcopping called 'Homestake," with part of the Opportunity rover visible. Credit: NASA/JPL. Colorization courtesy Stu Atkinson.
But behind Oppy was a most intriguing light-colored rock outcropping – this one was named “Homestake.” The rover spent several days studying the rock – even doing what could be termed a cruel drive-by (or driver-over). You can see in this image below, how Oppy really created havoc and a mess with her studies of this region:
A before-and-after montage of the Homestake outcropping, before and after the Opportunity rover drover over the rocks. Credit: NASA/JPL. Color and montage by Stu Atkinson
…leading Stu Atkinson to create this:
But seriously, many Mars rover fans are anxiously waiting to hear from the science team about what they found during Oppy’s close-up studies of this unusual rock outcropping.
Opportunity’s odometer reading is now over 21.33 miles (34,328.09 meters, or 34.33 kilometers).
Nancy Atkinson is Universe Today's Senior Editor. She also is the project manager for the 365 Days of Astronomy podcast, works with Astronomy Cast and is host of the NASA Lunar Science Institute podcast. Nancy is also a NASA/JPL Solar System Ambassador.
A 1972-era TV image of Mars' north polar cap. [more]
Jack Holt of the University of Texas and his graduate student Isaac Smith used radar data from MRO's Shallow Subsurface Radar to crack the case. Examining the details of this new data set has laid open the ice cap's internal structure, revealing clues to the massive ice troughs' formation.
Apparently, the wind did it.
"Radar cross sections reveal layers of ice deposited throughout the ice cap's history," says Holt. "The size and shape of those layers indicate that wind has played a key role in creating and shaping the spiral troughs."
Not only does wind shape the spirals, but also it causes them to move. They rotate around the north pole, turning like an excruciatingly slow pinwheel, curiously enough, against the wind.
Smith explains the process: "Cold air from the top of the ice cap sweeps down the slope, gaining speed and picking up water vapor and ice particles along the way. As this wind blows across the trough and starts up the other slope (the cooler side, facing away from the sun), it slows and precipitates the ice it holds. All of this ice is deposited on this cool slope, building it up, so the trough actually grows and migrates, over time, against the wind."
Alan Howard of the University of Virginia first suggested the ice trough migration model based on Viking spacecraft data back in 1982. His theory, that wind erosion and sunlight shape and move the troughs, was never widely accepted, but the new data supports it. [larger image]
The Coriolis force generated by Mars' rotation twists the winds sweeping down from the ice cap.
"That explains the troughs' spiral design," says Smith.
Similar formations can be found in Antarctic regions of Earth, but without the spiral shape.
Icy megadunes in Antarctica do not spiral like the ice troughs of Mars. [more]
"You don't see spirals in Earth's Antarctic ice sheet because local topography there prevents the winds from being steered by the Coriolis force."
The radar data have solved another icy mystery, too--the origin of Chasma Boreale.
Chasma Boreale is a Grand Canyon-sized chasm that slashes through the midst of the spiraled troughs. Theories to date suggested that either wind erosion or a single melt event excavated Chasma Boreale within the past 5 to 10 million years.
"Not so," says Holt. "The MRO data clearly show the chasm formed [long before the spirals did] in a much older ice sheet dating back billions of years. Due to the shape of that ancient sheet, the chasm grew deeper as newer ice deposits built up around it. Winds sweeping across the ice cap likely prevented new ice from building up inside the chasm [so it never filled up]."
The radar data also revealed a second chasm matching Boreale in size.
Chasma Boreale is indicated by an arrow in this modern image of the Martian north pole. [more]
"This chasm's never been seen before -- unlike Boreale, it did fill up with ice, probably because it's in a different location. Boreale is closer to the highest points of the ancient ice cap, where the winds are stronger and more consistent."
By discovering that both Chasma Boreale and the ice troughs were shaped by similar processes over different timescales, Holt and Smith answer some questions about Martian climate history. But they're also sparking new ones.
"For a long stretch of Martian history the ice layers were regular and uniform, then there was a distinct period when the spiral ice troughs got started," says Smith. "Something changed. There must have been a very fast (relatively speaking) and powerful change in climate. We still don't know what that change was."
"To figure that out, we need to look at the rest of Mars for evidence of other changes at that same time," says Holt. "This is just the tip of the ice berg."
THE ASTRONOMY PICTURE OF THE DAY FOR 2010 March 17
Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA
Explanation: Why is this small object orbiting Mars? The origin of Phobos, the larger of the two moons orbiting Mars, remains unknown. Phobos and Deimos appear very similar to C-type asteroids, yet gravitationally capturing such asteroids, circularizing their orbits, and dragging them into Mars' equatorial plane seems unlikely. Pictured above is Phobos as it appeared during last week's flyby of ESA's Mars Express, a robotic spacecraft that began orbiting Mars in 2003. Visible in great detail is Phobos' irregular shape, strangely dark terrain, numerous unusual grooves, and a spectacular chain of craters crossing the image center. Phobos spans only about 25 kilometers in length and does not have enough gravity to compress it into a ball. Phobos orbits so close to Mars that sometime in the next 20 million years, tidal deceleration will break up the rubble moon into a ring whose pieces will slowly spiral down and crash onto the red planet. The Russian mission Phobos-Grunt is scheduled to launch and land on Phobos next year.
THE ASTRONOMY PICTURE OF THE DAY FOR 2010 December 1
Credit: G. Neukum (FU Berlin) et al., Mars Express, DLR, ESA; Acknowledgement: Peter Masek
Explanation: Why is Phobos so dark? Phobos, the largest and innermost of two Martian moons, is the darkest moon in the entire Solar System. Its unusual orbit and color indicate that it may be a captured asteroid composed of a mixture of ice and dark rock. The above picture of Phobos near the limb of Mars was captured last month by the robot spacecraft Mars Express currently orbiting Mars. Phobos is a heavily cratered and barren moon, with its largest crater located on the far side. From images like this, Phobos has been determined to be covered by perhaps a meter of loose dust. Phobos orbits so close to Mars that from some places it would appear to rise and set twice a day, but from other places it would not be visible at all. Phobos' orbit around Mars is continually decaying -- it will likely break up with pieces crashing to the Martian surface in about 50 million years.
ASTRONOMY PICTURE OF THE DAY FOR 2010 March 1
Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Explanation: What creates these picturesque dark streaks on Mars? No one knows for sure. A leading hypothesis is that streaks like these are caused by fine grained sand sliding down the banks of troughs and craters. Pictured above, dark sand appears to have flowed hundreds of meters down the slopes of Acheron Fossae. The sand appears to flow like a liquid around boulders, and, for some reason, lightens significantly over time. This sand flow process is one of several which can rapidly change the surface of Mars, with other processes including dust devils, dust storms, and the freezing and melting of areas of ice. The above image was taken by the HiRise camera on board the Mars Reconnaissance Orbiter which has been orbiting Mars since 2006. Acheron Fossae is a 700 kilometer long trough in the Diacria quadrangle of Mars.
THE ASTRONOMY PICTURE OF THE DAY FOR 2010 January 19
Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Explanation: They might look like TREES on Mars, but they're NOT. Groups of dark brown streaks have been photographed by the Mars Reconnaissance Orbiter on melting pinkish sand dunes covered with light frost. The above image was taken in 2008 April near the North Pole of Mars. At that time, dark sand on the interior of Martian sand dunes became more and more visible as the spring Sun melted the lighter carbon dioxide ice. When occurring near the top of a dune, dark sand may cascade down the dune leaving dark surface streaks -- streaks that might appear at first to be trees standing in front of the lighter regions, but cast no shadows. Objects about 25 centimeters across are resolved on this image spanning about one kilometer. Close ups of some parts of this image show billowing plumes indicating that the sand slides were occurring even when the image was being taken.
Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Explanation: Stickney Crater, the largest crater on the martian moon Phobos, is named for Chloe Angeline Stickney Hall, mathematician and wife of astronomer Asaph Hall. Asaph Hall discovered both the Red Planet's moons in 1877. Over 9 kilometers across, Stickney is nearly half the diameter of Phobos itself, so large that the impact that blasted out the crater likely came close to shattering the tiny moon. This stunning, enhanced-color image of Stickney and surroundings was recorded by the HiRISE camera onboard the Mars Reconnaissance Orbiter as it passed within some six thousand kilometers of Phobos in March of 2008. Even though the surface gravity of asteroid-like Phobos is less than 1/1000th Earth's gravity, streaks suggest loose material has slid down inside the crater walls over time. Light bluish regions near the crater's rim could indicate a relatively freshly exposed surface. The origin of the curious grooves along the surface is mysterious but may be related to the crater-forming impact.
THE ASTRONOMY PICTURE OF THE DAY FOR 2009 March 16
Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Explanation: Mars has two tiny moons, Phobos and Deimos. Pictured above, in a recently release image by HiRISE camera onboard the Mars-orbiting Mars Reconnaissance Orbiter (MRO), is Deimos, the smaller moon of Mars. Deimos is one of the smallest known moons in the Solar System measuring only about 15 kilometers across. The diminutive Martian moon was discovered in 1877 by Asaph Hall, an American astronomer working at the US Naval Observatory in Washington D.C. The existence of two Martian moons was predicted around 1610 by Johannes Kepler, the astronomer who derived the laws of planetary motion. In this case, Kepler's prediction was not based on scientific principles, but his writings and ideas were so influential that the two Martian moons are discussed in works of fiction such as Jonathan Swift's Gulliver's Travels, written in 1726, over 150 years before their actual discovery.
AMAZING UPDATE FROM NASA:
ASTRONOMY PICTURE OF THE DAY for 2009 January 20
USE TOOL BAR SLIDE BELOW TO SCROLL TO THE RIGHT TO SEE THIS FULL PANORAMIC VIEW
Credit: Mars Exploration Rover Mission, Cornell, JPL, NASA
Explanation: If you could stand on Mars -- what could you see? One memorable vista might be the above 360-degree panoramic image taken by the robotic Spirit rover over the last year. The above image involved over 200 exposures and was released as part of Spirit's five year anniversary of landing on the red planet. The image was taken from the spot that Spirit stopped to spend the winter, near an unusual plateau called Home Plate. Visible on the annotated image are rocks, hills, peaks, ridges, plains inside Gusev crater, and previous tracks of the rolling Spirit rover. The image color has been closely matched to what a human would see, and named for the famous space artist Chesley Bonestell.
UNIVERSETODAY.COM FOR March 2nd, 2009
Written by Nancy Atkinson
A new study of gullies seen on Mars provides evidence that water flowed recently on the Red Planet, at least in geologic terms. Planetary geologists at Brown University have found a gully fan system on Mars that formed only about 1.25 million years ago. The structure of this fan offers compelling evidence that it was formed by melt water that originated in nearby snow and ice deposits. This time frame may be the most recent period when water flowed on the planet. This most recent finding comes on the heels of discoveries of water-bearing minerals such as opals and carbonates, and together all these discoveries provide clues that Mars was, at least occasionally, wetter and warmer for far longer than previously thought.
While gullies are known to be young surface features, it's difficult to date them. But the Brown scientists were able to date the gully system because of craters in the area, and also hypothesize what water was doing there.
The gully system shows four intervals where water-borne sediments were carried down the steep slopes of nearby alcoves and deposited in alluvial fans, said Samuel Schon, a Brown graduate student and the paper's lead author.
"You never end up with a pond that you can put goldfish in," Schon said, "but you have transient melt water. You had ice that typically sublimates. But in these instances it melted, transported, and deposited sediment in the fan. It didn't last long, but it happened."
The gully system is located on the inside of a crater in Promethei Terra, an area of cratered highlands in the southern mid-latitudes. The eastern and western channels of the gully each run less than a kilometer from their alcove sources to the fan deposit.
Viewed from afar, the fan appears as one entity several hundred meters wide. But by zooming in with the HiRISE camera aboard the Mars Reconnaissance Orbiter, Schon was able to distinguish four individual lobes in the fan, and determine that each lobe was deposited separately. Moreover, Schon was able to identify the oldest lobe, because it was pockmarked with small craters, while the other lobes were unblemished, meaning they had to be younger.
Next came the task of trying to date the secondary craters in the fan. Schon linked the craters on the oldest lobe to a rayed crater more than 80 kilometers to the southwest. Using well-established techniques, Schon dated the rayed crater at about 1.25 million years, and so established a maximum age for the younger, superimposed lobes of the fan.
The team determined that ice and snow deposits formed in the alcoves at a time when Mars had a high obliquity (its most recent ice age) and ice was accumulating in the mid-latitude regions. Sometime around a half-million years ago, the planet's obliquity changed, and the ice in the mid-latitudes began to melt or, in most instances, changed directly to vapor. Mars has been in a low-obliquity cycle ever since, which explains why no exposed ice has been found beyond the poles.
The team tested other theories of what the water may have been doing in the gully system. The scientists ruled out groundwater bubbling to the surface, Schon said, because it seemed unlikely to have occurred multiple times in the planet's recent history. They also don't think the gullies were formed by dry mass wasting, a process by which a slope fails as in a rockslide. The best explanation, Schon said, was the melting of snow and ice deposits that created "modest" flows and formed the fan.
The team's findings appear in the March issue of Geology.
Source: Brown University
From UniverseToday.com for November 7th, 2009
Written by Nancy Atkinson
Oh, and rumor has it that the extrication process may have begun to free the Spirit rover. Latest images show she has moved every so slightly. More as it becomes available….
THE ASTRONOMY PICTURE OF THE DAY for 2009 January 19
Explanation: Why is there methane on Mars? No one is sure. An important confirmation that methane exists in the atmosphere of Mars occurred last week, bolstering previous controversial claims made as early as 2003. The confirmation was made spectroscopically using large ground-based telescopes by finding precise colors absorbed on Mars that match those absorbed by methane on Earth. Given that methane is destroyed in the open martian air in a matter of years, the present existence of the fragile gas indicates that it is currently being released, somehow, from the surface of Mars. One prospect is that microbes living underground are creating it, or created in the past. If true, this opens the exciting possibility that life might be present under the surface of Mars even today. Given the present data, however, it is also possible that a purely geologic process, potentially involving volcanism or rust and not involving any life forms, is the methane creator. Pictured above is an image of Mars superposed with a map of the recent methane detection.
THE ASTRONOMY PICTURE OF THE DAY for 2009 January 10
Credit: Mars Exploration Rover Mission, Texas A&M, Cornell, JPL, NASA
Explanation: This month, the Mars Exploration Rovers are celebrating their 5th anniversary of operations on the surface of the Red Planet. The serene sunset view, part of their extensive legacy of images from the martian surface, was recorded by the Spirit rover on May 19, 2005. Colors in the image have been slightly exaggerated but would likely be apparent to a human explorer's eye. Of course, fine martian dust particles suspended in the thin atmosphere lend the sky a reddish color, but the dust also scatters blue light in the forward direction, creating a bluish sky glow near the setting Sun. The Sun is setting behind the Gusev crater rim wall some 80 kilometers (50 miles) in the distance. Because Mars is farther away, the Sun is less bright and only about two thirds the diameter seen from planet Earth.
ASTRONOMY PICTURE OF THE DAY for 2008 November 24
Data Reconstruction Credit : NASA/JPL-Caltech/UTA/UA/MSSS/ESA/DLR/JPL Solar System Visualization Project
Explanation: What created this unusual terrain on Mars? The floors of several mid-latitude craters in Hellas Basin on Mars appear unusually grooved, flat, and shallow. New radar images from the Mars Reconnaissance Orbiter bolster an exciting hypothesis: huge glaciers of buried ice. Evidence indicates that such glaciers cover an area larger than a city and extend as much as a kilometer deep. The ice would have been kept from into the evaporating thin Martian air by a covering of dirt. If true, this would indicate the largest volume of water ice outside of the Martian poles, much larger than the frozen puddles recently discovered by the Phoenix lander. Such lake-sized ice blocks located so close to the Martian equator might make a good drinking reservoir for future astronauts exploring Mars. How the glaciers originally formed remains a mystery. In the meantime, before packing up to explore Mars, please take a moment to suggest a name for NASA's next Martian rover.
December 01, 2008
PASADENA, Calif. -- After nearly a month of daily checks to determine whether Martian NASA's Phoenix Mars Lander would be able to communicate again, the agency has stopped using its Mars orbiters to hail the lander and listen for its beep.
As expected, reduced daily sunshine eventually left the solar-powered Phoenix craft without enough energy to keep its batteries charged.
The final communication from Phoenix remains a brief signal received via NASA's Mars Odyssey orbiter on Nov. 2. The Phoenix lander operated for two overtime months after achieving its science goals during its original three-month mission. It landed on a Martian arctic plain on May 25.
"The variability of the Martian weather was a contributing factor to our loss of communications, and we were hoping that another variation in weather might give us an opportunity to contact the lander again," said Phoenix Mission Manager Chris Lewicki of NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The end of efforts to listen for Phoenix with Odyssey and NASA's Mars Reconnaissance Orbiter had been planned for the start of solar conjunction, when communications between Earth and Mars-orbiting spacecraft are minimized for a few weeks. That period, when the sun is close to the line between Earth and Mars, has begun and will last until mid-December.
The last attempt to listen for a signal from Phoenix was when Odyssey passed overhead at 3:49 p.m. PST Saturday, Nov. 29 (4:26 p.m. local Mars solar time on the 182nd Martian day, or sol, since Phoenix landed). Nov. 29 was selected weeks ago as the final date for relay monitoring of Phoenix because it provided several weeks to the chance to confirm the fate of the lander, and it coincided with the beginning of solar conjunction operations for the orbiters. When they come out of the conjunction period, weather on far-northern Mars will be far colder, and the declining sunshine will have ruled out any chance of hearing from Phoenix.
The Phoenix mission is led by Peter Smith of the University of Arizona, Tucson, with project management at JPL and development partnership at Lockheed Martin, Denver. International contributions come from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus in Denmark; the Max Planck Institute in Germany; the Finnish Meteorological Institute; and Imperial College, London. The California Institute of Technology in Pasadena manages JPL for NASA.
Media contact: Guy Webster 818-354-6278
Jet Propulsion Laboratory, Pasadena, Calif.
BELOW SHOW MARS TO THE LEFT OF THE BEEHIVE CLUSTER (M44)
TIMEKEEPING ON MARS
Mars has an axial tilt and a rotation period similar to those of Earth. Thus it experiences seasons of spring, summer, autumn and winter much like Earth, and its day is about the same length. Its year, however, is almost twice as long as Earth's, and its orbital eccentricity is considerably larger, which means among other things that the lengths of various Martian seasons differ considerably,
and sundial time can diverge from clock time much more than on Earth.
The average length of a Martian sidereal day is 24h 37m 22.663s (based on SI units), and the length of its solar day (often called a sol) is 88,775.24409 seconds or 24h 39m 35.24409s. The corresponding values for Earth are 23h 56m 04.2s and 24h 00m 00.002s, respectively. This yields a conversion factor of 1.027491 days/sol. Thus Mars's solar day is only about 2.7% longer than Earth's.
A convention used by spacecraft lander projects to date has been to keep track of local solar time using a 24 hour "Mars clock" on which the hours, minutes and seconds are 2.7% longer than their standard (Earth) durations. For the Mars Pathfinder, Mars Exploration Rover, and Phoenix missions, the operations team has worked on "Mars time", with a work schedule synchronized to the local time
at the landing site on Mars, rather than the Earth day. This results in the crew's schedule sliding approximately 40 minutes later in Earth time each day. Wristwatches calibrated in Martian time, rather than Earth time, were used by many of the MER team members.
Local solar time has a significant impact on planning the daily activities of Mars landers. Daylight is needed for the solar panels. Temperatures rise and fall rapidly at sunrise and sunset, because Mars lacks Earth's thick atmosphere and oceans which buffer such fluctuations.
Alternative clocks for Mars have been proposed, but no mission has chosen to use such. These include a metric time schema, with "millidays" and "centidays", and an extended day which uses standard units but which counts to 24hr 39m 35s before ticking over to the next day. Kim Stanley Robinson's science fiction Mars Trilogy describes digital clocks that use standard minutes and hours but freeze for
a "timeslip" of roughly 39 minutes at midnight.Telling Time on Mars By Michael Allison — January 1998
As on Earth, on Mars there is also an equation of time that represents the difference between sundial time and uniform (clock) time. The equation of time is illustrated by an analemma. Because of orbital eccentricity, the length of the solar day is not quite constant. Because its orbital eccentricity is greater than that of Earth, the length of day varies from the average by a greater amount than that of Earth, and hence its equation of time shows greater variation than that of Earth: on Mars, the Sun can run 50 minutes slower or 40 minutes faster than a Martian clock (on Earth, the corresponding figures are 14min 22sec slower and 16min 23sec faster).
Mars has a prime meridian, defined as passing through the small crater Airy-0. However, Mars does not have time zones defined at regular intervals from the prime meridian, as on Earth. Each lander so far has used an approximation of local solar time as its frame of reference, as cities did on Earth before the introduction of standard time in the 19th century. (The two Mars Exploration Rovers happen to
be approximately 12 hours and one minute apart.)
Note that the modern standard for measuring longitude on Mars is "planetocentric longitude", which is measured from 0°–360° East and measures angles from the center of Mars. The older "planetographic longitude" was measured from 0°–360° West and used coordinates mapped onto the surface.
MTC is a proposed Mars analog to Universal Time (UT) on Earth. It is defined as the mean solar time at Mars's prime meridian (i.e., at the centre of the crater Airy-0). The name "MTC" is intended to parallel the Terran Coordinated Universal Time (UTC), but this is somewhat misleading: what distinguishes UTC from other forms of UT is its leap seconds, but MTC does not use any such scheme. MTC is more closely analogous to UT1.
Use of the term "MTC" as the name of a planetary standard time for Mars first appeared in the Mars24 sunclock coded by the NASA Goddard Institute for Space Studies. It replaced Mars24's previous use of the term "Airy Mean Time" (AMT), which was a direct parallel of Greenwich Mean Time (GMT). In an astronomical context, "GMT" is a deprecated name for Universal Time, or sometimes more specifically for UT1.
AMT has not yet been employed in official mission timekeeping. This is partially attributable to uncertainty regarding the position of Airy-0 (relative to other longitudes), which meant that AMT couldn't be realized as accurately as local time at points being studied. At the start of the Mars Exploration Rover missions, the positional uncertainty of Airy-0 corresponded to roughly a 20 second uncertainty in realizing AMT.
Each lander mission so far has used its own timezone, corresponding to average local solar time at the landing location. Of the six successful Mars landers to date, five employed offsets from local mean solar time (LMST) for the lander site while the sixth (Mars Pathfinder) used local true solar time (LTST).
Mars Pathfinder used local apparent solar time at the landing location. Its timezone was AAT-02:13:01, where "AAT" is Airy Apparent Time, meaning apparent solar time at Airy-0.
The two Mars Exploration Rovers don't use precisely the LMST of the landing points. For mission operations purposes, they defined a time scale that would match the clock used for the mission to the apparent solar time about halfway through the nominal 90-sol prime mission. This is referred to in mission planning as "Hybrid Local Solar Time". The time scales are uniform in the sense of mean solar time (they are actually mean time of some longitude), and are not adjusted as the rovers travel. (The rovers have travelled distances that make a few seconds difference to local solar time.) Spirit uses AMT+11:00:04. Mean solar time at its landing site is AMT+11:41:55. Opportunity uses AMT-01:01:06. Mean solar time at its landing site is AMT-00:22:06. Neither rover is likely to ever reach the longitude at which its mission time scale matches local mean time. For science purposes, Local True Solar Time is used.
With the location of Airy-0 now known much more precisely than when these missions landed, it is technically feasible for future missions to use a convenient offset from Airy Mean Time, rather than completely non-standard timezones.
When a spacecraft lander begins operations on Mars, it keeps track of the passing Martian days (sols) by a simple numerical count. The two Viking missions and Mars Phoenix count the sol on which each lander touched down as "Sol 0"; Mars Pathfinder and the two Mars Exploration Rovers instead defined touchdown as "Sol 1".
Although lander missions have twice occurred in pairs, no effort was made to synchronize the sol counts of the two landers within each pair. Thus, for example, although Spirit and Opportunity were sent to operate simultaneously on Mars, each counted its landing date as "Sol 1", putting their calendars approximately 21 sols out of synch. Spirit and Opportunity differ in longitude by 179 degrees, so when it is daylight for one it is night for the other, and they carry out activities independently.
On Earth, astronomers often use Julian dates – a simple sequential count of days – for timekeeping purposes. A proposed counterpart on Mars is the Mars Sol Date, or MSD, which is a running count of sols since approximately December 29, 1873. Some[who?] prefer a start date (or epoch) around the year 1608; either choice is intended to ensure that all historically recorded events related to Mars occur after it. The Mars Sol Date is defined mathematically as MSD = (Julian date using International Atomic Time - 51549.0 + k)/1.02749125 + 44796.0, where k is a small correction of approximately 0.00014 d (or 12 s) due to uncertainty in the exact geographical position of the prime meridian at Airy-0 crater.
The word "yestersol" was coined by the NASA Mars operations team early during the MER mission to refer to the previous sol (the Mars version of "yesterday") and came into fairly wide use within that organization during the Mars Exploration Rover Mission of 2003. It was even picked up and used by the press. Other neologisms such as "tosol" (for "today") and "nextersol" or "morrowsol" (for "tomorrow") were less successful.
Mars scientists typically keep track of the Martian year by use of the heliocentric longitude (or "seasonal longitude"), typically abbreviated Ls, the position of Mars in its orbit around the Sun. Ls is defined as 0 degrees at the Martian northward equinox, and hence is 90 degrees at the Martian northern solstice, 180 at the Martian southward equinox, and 270 degrees at the Martian southern solstice.
For most day-to-day activities on Earth, people don't use Julian days, but the Gregorian calendar, which despite its various complications is quite useful. It allows for easy determination of whether one date is an anniversary of another, whether a date is in winter or spring, and what is the number of years between two dates. This is much less practical with Julian days count.
For similar reasons, if it is ever necessary to schedule and co-ordinate activities on a large scale across the surface of Mars it would be necessary to agree on a calendar. One proposed calendar is the Darian calendar. It has 24 "months", to accommodate the longer Martian year while keeping the notion of a "month" that is reasonably similar to the length of an Earth month. On Mars, a "month" would have no relation to the orbital period of any moon of Mars, since Phobos and Deimos orbit in about 7 hours and 30 hours respectively. However, Earth and Moon would generally be visible to the naked eye when they were above the horizon at night, and the time it takes for the Moon to move from maximum separation in one direction to the other and back as seen from Mars is close to a Lunar month. Neither the Darian calendar nor any other Martian calendar is currently in use.
This length of time for Mars to complete one orbit around the Sun is its sidereal year, and is about 686.98 Earth solar days, or 668.5991 sols. Because of the eccentricity of Mars' orbit, the seasons are not of equal length. Assuming that seasons run from equinox to solstice or vice versa, the season Ls 0 to Ls 90 (northern-hemisphere spring / southern-hemisphere autumn) is the longest season lasting
194 Martian sols, and Ls 180 to Ls 270 (northern hemisphere autumn / southern-hemisphere spring) is the shortest season, lasting only 142 Martian sols.
As on Earth, the sidereal year is not the quantity that is needed for calendar purposes. Rather, the tropical year would be likely to be used because it gives the best match to the progression of the seasons. It is slightly shorter than the sidereal year due to the precession of Mars' rotational axis. The precession cycle is 93,000 Martian years (175,000 Earth years), much longer than on Earth. Its length in tropical years can be computed by dividing the difference between the sidereal year and tropical year by the length of the tropical year.
Tropical year length depends on the starting point of measurement, due to the effects of Kepler's second law of planetary motion. It can be measured in relation to an equinox or solstice, or can be the mean of various possible years including the March (northward) equinox year, June (northern) solstice year, the September (southward) equinox year, the December (southern) solstice year, and other such years. The Gregorian calendar uses the March equinox year.
On Earth, the variation in the lengths of the tropical years is small, but on Mars it is much larger. The northward equinox year is 668.5907 sols, the northern solstice year is 668.5880 sols, the southward equinox year is 668.5940 sols, and the southern solstice year is 668.5958 sols. Averaging over an entire orbital period gives a tropical year of 668.5921 sols. (Since, like Earth, the northern and southern hemispheres of Mars have opposite seasons, equinoxes and solstices must be labelled by hemisphere to remove ambiguity.)
Any calendar must use intercalation (leap years) to make up for the fact that a year is not equivalent to an integer number of days. Without intercalation, the year will accumulate errors over time. Most designs for Martian calendars intercalate single days, but a few use an intercalary week. The time system currently used by Mars scientists, basing the seasonal date on Mars based on the heliocentric longitude, obviates the need for intercalation by not marking time in terms of days, but instead in terms of Mars' position in orbit.
For the Gregorian (Earth) calendar, the leap-year formula is every 4th year except for every 100th year except for every 400th year, which produces an average calendar year length of 365.2425 solar days, close to the Earth equinox year. On Mars, a similar intercalation scheme for leap years would be needed. If the calendar intercalates single days, the majority of years would be leap years because the fractional sol – the remainder of a sol left each year after a whole number of days has passed – is more than 0.5. This also happens to be true if the calendar is a leap-week calendar with weeks of seven days. One example intercalation, having a leap day every odd year or year ending in 0 except every 100th year, except every 500th year, would produce an average year of 668.592 sols: , which would be nearly perfect for the mean tropical year (average of all seasons). The scheme, however, would depend slightly on exactly which year was adopted for calendar purposes: calendars based on the southern solstice year or on the northward equinox year would differ by one sol in as little as two hundred or so Martian years.
The proposed Darian calendar uses the northward equinox year length of 668.5907 sols as the basis of its intercalation scheme.
Other intercalation schemes are possible. For example, the Hebrew Calendar (a lunisolar calendar) uses a simple mathematical formula to intercalate seven extra months in a 19-year cycle: a month is inserted if the remainder of (Hebrew Year Number × 7 + 1) / 19 is less than 7. (The leap year rule is specified differently but is mathematically equivalent.) Such an intercalation scheme would insert the leap years in a more evenly-spaced pattern than Gregorian-based rules, and unlike Gregorian-based rules would have no exceptions. To create a similar intercalation scheme for a Martian calendar, one must find a fractional equivalent for the year length, often using continued fractions to reduce the size of the fractions. For example, an intercalation scheme that intercalates single days and is based on the mean Martian tropical year of 668.5921 days can be approximated closely with a cycle of 45 leap years in 76 years because 66845⁄76 ≈ 668.592105 and 0.5921 × 76 = 44.9996.
In Kim Stanley Robinson's Mars Trilogy, clocks retain Earth-standard seconds, minutes and hours, but freeze at midnight for 39.5 minutes. As the fictional colonization of Mars progresses, this "timeslip" becomes a sort of witching hour, a time when inhibitions can be shed and the emerging identity of Mars as a separate entity from Earth is celebrated. (It is not said explicitly whether this occurs simultaneously all over Mars, or at local midnight in each longitude.) Philip K. Dick's much earlier Martian Time-Slip deals with the vagaries as well.[clarification needed]
Also in the Mars Trilogy, the calendar year is divided into twenty-four months. The names of the months are the same as the Gregorian calendar, except for a "1" or "2" in front to indicate the first or second occurrence of that month (e.g. 1 January, 2 January, 1 February, 2 February, etc.) In the manga and anime series Aria by Kozue Amano, set on a terraformed Mars, the calendar year is also divided into twenty-four months. Following modern Japanese practice, the months are not named but numbered sequentially, running from 1st Month to 24th Month.