What Does Earth Look like from Mars?

Modern astronomy and space exploration has blessed us with a plethora of wonderful images. Whether they were images of distant planets, stars and galaxies taken by Earth-based telescopes, or close-ups of planets or moons in our own Solar System by spacecraft, there has been no shortage of inspiring pictures. But what would it look like to behold planet Earth from another celestial body?

We all remember the breathtaking photos taken by the Apollo astronauts that showed what Earth looked like from the Moon. But what about our next exploration destination, Mars? With all the robotic missions on or in orbit around the Red Planet, you’d think that there would have been a few occasions where they got a good look back at Earth. Well, as it turn out, they did!

Pictures from Space:

Pictures of Earth have been taken by both orbital missions and surface missions to Mars. The earliest orbiters, which were part of the Soviet Mars and NASA Mariner programs, began arriving in orbit around Mars by 1971. NASA’s Mariner 9 probe was the first to establish orbit around the planet’s (on Nov. 14, 1971), and was also the first spacecraft to orbit another planet.

Image of Earth and Moon, taken by the Mars Orbiter Camera of Mars Global Surveyor on May 8 2003. Credit: NASA/JPL/Malin Space Science Systems
Image of Earth and Moon, taken by the Mars Orbiter Camera of Mars Global Surveyor on May 8 2003. Credit: NASA/JPL/Malin Space Science Systems

The first orbiter to capture a picture of Earth from Mars, however, was the Mars Global Surveyor, which launched in Nov. 7th, 1996, and arrived in orbit around the planet on Sept. 12th, 1997. In the picture (shown above), which was taken in 2003, we see Earth and the Moon appearing closely together.

At the time the picture was taken, the distance between Mars and Earth was 139.19 million km (86.49 million mi; 0.9304 AU) while the distance between Mars and the Moon was 139.58 million km (86.73 million mi; 0.9330 AU). Interestingly enough, this is what an observer would see from the surface of Mars using a telescope, whereas a naked-eye observer would simply see a single point of light.

Usually, the Earth and Moon are visible as two separate points of light, but at this point in the Moon’s orbit they were too close to resolve with the naked eye from Mars. If you look closely at Earth, you can just make out the shape of South America.

Earth and the Moon, captured by the Mars Express spacecraft on July 3, 2003. Credit: ESA
Earth and the Moon, captured by the Mars Express spacecraft on July 3, 2003. Credit: ESA

The picture above was snapped by the Mars Express’s High Resolution Stereo Camera (HRSC) on the ESA’s Mars Express probe. It was also taken in 2003, and is similar in that it shows the Earth and Moon together. However, in this image, we see the two bodies at different points in their orbit – which is why the Moon looks like its farther away. Interestingly enough, this image was actually part of the first data sets to be sent by the spacecraft.

The next orbiter to capture an image of Earth from Mars was the Mars Reconnaissance Orbiter (MRO), which was launched in August of 2005 and attained Martian orbit on March 10th, 2006. When the probe reached Mars, it joined five other active spacecraft that were either in orbit or on the surface, which set a record for the most operational spacecraft in the vicinity of Mars at the same time.

In the course of its mission – which was to study Mars’ surface and weather conditions, as well as scout potential landing sites – the orbiter took many interesting pictures. The one below was taken on Oct. 3rd, 2007, which showed the Earth and the Moon in the same frame.

Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (HiRISE) camera can also be used to view other planets. MRO took this image of the Earth and the Moon on 3 October 2007. Credit: NASA/JPL
Image of Earth and the Moon taken by the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE) on Oct. 3rd, 2007. Credit: NASA/JPL

Pictures from the Surface:

As noted already, pictures of Earth have also been taken by robotic missions to the surface of Mars. This has been the case for as long as space agencies have been sending rovers or landers that came equipped with mobile cameras. The earliest rovers to reach the surface – Mars 2 and Mars 3– were both sent by the Soviets.

However, it was not until early March of 2004, while taking photographs of the Martian sky, that the Spirit rover became the first to snap a picture of Earth from the surface of another planet. This image was caught while the rover was attempting to observe Mars’ moon Deimos making a transit of the Sun (i.e. a partial eclipse).

This is something which happens quite often given the moon’s orbital period of about 30 hours. However, on this occasion, the rover managed to also capture a picture of distant Earth, which appeared as little more than a particularly bright star in the night sky.

Earth as seen from Mars, shortly before daybreak. This is the first image of the Earth from the surface of another planet. Credit: NASA/JPL
Earth seen from Mars shortly before daybreak. This is the first image of the Earth from the surface of another planet. Credit: NASA/JPL

The next rover to snap an image of Earth from the Martian surface was Curiosity, which began sending back many breathtaking photos even before it landed on Aug. 6th, 2012. And on Jan. 31st, 2014 – almost a year and a half into its mission – the rover managed to capture an image of both Earth and the Moon in the night sky.

In the image (seen below), Earth and the Moon are just visible as tiny dots to the naked eye – hence the inset that shows them blown up for greater clarity. The distance between Earth and Mars when Curiosity took the photo was about 160 million km (99 million mi).

Earth has been photographed from Mars several times now over the course of the past few decades. Each picture has been a reminder of just how far we’ve come as a species. It also provides us with a preview of what future generations may see when looking out their cabin window, or up at the night sky from other planets.

Image taken by NASA's Curiosity Mars rover, showing Earth and the Moon shining in the night sky. Credit: NASA/JPL
Image taken by NASA’s Curiosity Mars rover, showing Earth and the Moon shining in the night sky. Credit: NASA/JPL

We have written many interesting articles about Earth and Mars here at Universe Today. Here’s Incredible Image of Mars from Earth, Mars Compared to Earth, How Far is Mars from Earth, and How Long Does it Take to get to Mars?

For more information, be sure to check out NASA’s Solar System Exploration page on Mars.

Astronomy Cast also has an interesting episode on the subject – Episode 52: Mars

Sources:

How Many Moons Does Mars Have?

Many of the planets in our Solar System have a system of moons. But among the rocky planets that make up the inner Solar System, having moons is a privilege enjoyed only by two planets: Earth and Mars. And for these two planets, it is a rather limited privilege compared to gas giants like Jupiter and Saturn which each have dozens of moons.

Whereas Earth has only one satellite (aka. the Moon), Mars has two small moons: Phobos and Deimos. And whereas the vast majority of moons in our Solar System are large enough to become round spheres similar to our own Moon, Phobos and Deimos are asteroid-sized and misshapen in appearance.

Size, Mass and Orbit:

The larger moon is Phobos, whose name comes from the Greek word which means “fear” (i.e. phobia). Phobos measures just 22.7 km across and has an orbit that places it closer to Mars than Deimos. Compared to Earth’s own Moon — which orbits at a distance of 384,403 km away from our planet — Phobos orbits at an average distance of only 9,377 km above Mars.

This produces an orbit of short duration, revolving around the planet three times in a single day. For someone standing on the planet’s surface, Phobos could be seen crossing the sky in only 4 hours or so.

Phobos, the larger of Mars' two moons, with the Stickney crater seen on the right side. Credit: HiRISE, MRO, LPL (U. Arizona), NASA
Phobos, the larger of Mars’ two moons, with the Stickney crater seen on the right side. Credit: HiRISE, MRO, LPL (U. Arizona), NASA

Mars’ second moon is Deimos, which takes its name from the Greek word for panic. It is even smaller, measuring just 12.6 km across, and is also less irregular in shape. Its orbit places it much farther away from Mars, at a distance of 23,460 km, which means that Deimos takes 30.35 hours to complete an orbit around Mars.

When impacted, dust and debris will leave the surface of the moon because they do not have enough gravitational pull to retain the ejecta. However, the gravity from Mars will keep a ring of this debris around the planet in approximately the same region that the moon orbits. As the moon revolves, the debris is redeposited as a dusty layer on its surface.

Like Earth’s Moon, Phobos and Deimos always present the same face to their planet. Both are lumpy, heavily-cratered and covered in dust and loose rocks. They are among the darker objects in the solar system. The moons appear to be made of carbon-rich rock mixed with ice. Given their composition, size and shape, astronomers think that both of Mars’ moons were once asteroids that were captured in the distant past.

However, it appears that of these two satellites, Phobos won’t be orbiting the Red Planet for very much longer. Because it orbits Mars faster than the planet itself rotates, it is slowly spiraling inward. As a result, scientists estimate that in the next 10-50 million years or so, it will get so low that the Martian gravity will tear Phobos into a pile of rocks. And then a few million years later, those rocks will crash down on the surface of Mars in a spectacular string of impacts.

The Martian Moon of Deimos, as pictured by the Mars Reconnaissance Orbiter. Credit: HiRISE/MRO/LPL (U. Arizona)/NASA
The Martian Moon of Deimos, as pictured by the Mars Reconnaissance Orbiter. Credit: HiRISE/MRO/LPL (U. Arizona)/NASA

Composition and Surface Features:

Phobos and Deimos both appear to be composed of C-type rock, similar to blackish carbonaceous chondrite asteroids. This family of asteroids is extremely old, dating back to the formation of the Solar System. Hence, it is likely that they were acquired by Mars very early in its history.

Phobos is heavily cratered from eons worth of impacts from meteors with three large craters dominating the surface. The largest crater is Stickney (visible in the photo above). The Stickney crater is 10 km in diameter, which is almost half of the average diameter of Phobos itself. The crater is so large that scientists believe the impact came close to breaking the moon apart. Parallel grooves and striations leading away from the crater indicate that fractures were likely formed as a result of the impact.

Much like Phobos, it’s surface is pockmarked and cratered from numerous impact. The largest crater on Deimos is approximately 2.3 km in diameter (1/5 the size of the Stickney crater). Although both moons are heavily cratered, Deimos has a smoother appearance caused by the partial filling of some of its craters.

Origin:

Compared to our Moon, Phobos and Deimos are rough and asteroid-like in appearance, and also much smaller. In addition, their composition (as already noted) is similar to that of C-type asteroids that are common to the Asteroid Belt. Hence, the prevailing theory as to their origin is that they were once asteroids that were kicked out of the Main Belt by Jupiter’s gravity, and were then acquired by Mars.

 

History of Observation:

Phobos and Deimos were originally discovered by American astronomer Asaph Hall in August of 1877. Ninety-four years after the moons’ discovery, NASA’s Mariner 9 spacecraft got a much better look at the two moons from its orbit around Mars. Upon viewing the large crater on Phobos, NASA decided to name it after Hall’s wife – Stickney. Subsequent observations conducted by the HiRISE experiment, the Mars Global Surveyor, and the Mars Reconnaissance Orbiter have added to our overall understanding of these two satellites.

Someday, manned missions may be going to Phobos and Deimos. Scientists have discussed the possibility of using one of the Martian moons as a base from which astronauts could observe the Red Planet and launch robots to its surface, while shielded by miles of rock from cosmic rays and solar radiation for nearly two-thirds of every orbit.

Here’s an article about how Phobos is going to crash into Mars in the future. And here are some great images of both Phobos and Deimos.

Here’s NASA’s fact sheet on Mars, including information about the moons, and additional info from Starry Skies.

Finally, if you’d like to learn more about Mars in general, we have done several podcast episodes about the Red Planet at Astronomy Cast. Episode 52: Mars, and Episode 91: The Search for Water on Mars.

Sources:

Nobody Knows What These Mysterious Plumes are on Mars

In March 2012, amateur astronomers began observing unusual clouds or plumes along the western limb of the red planet Mars. The plumes, in the southern hemisphere rose to over 200 kilometers altitude persisting for several days and then reappeared weeks later.

So a group of astronomers from Spain, the Netherlands, France, UK and USA have now reported their analysis of the phenomena. Their conclusions are inconclusive but they present two possible explanations.

Was dust lofted to extreme altitudes or ice crystals transported into space.? Hubble images show cloud formations (left) and the effects of a global dust storm on Mars (Credit: NASA/Hubbble)
Was dust lofted to extreme altitudes or ice crystals transported into space.? Hubble images show cloud formations (left) and the effects of a global dust storm on Mars (Credit: NASA/Hubbble)

Mars and mystery are synonymous. Among Martian mysteries, this one has persisted for three years. Our own planet, much more dynamic than Mars, continues to raise new questions and mysteries but Mars is a frozen desert. Frozen in time are features unchanged for billions of years.

An animated sequence of images taken by Wayne Jaeschke on March 20, 2012 showing the mystery plume over the western limb of the red planet (upper right). South is up in the photo. (Credit: W. Jaeschke)

In March 2012, the news of the observations caught the attention of Universe Today contributing writer Bob King. Reported on his March 22nd 2012 AstroBob blog page, the plumes or clouds were clear to see. The amateur observer, Wayne Jaeschke used his 14 inch telescope to capture still images which he stitched together into an animation to show the dynamics of the phenomena.

ModernDay_Astrophotographer2Now on February 16 of this year, a team of researchers led by Agustín Sánchez-Lavega of the University of the Basque Country in Bilbao, Spain, published their analysis in the journal Nature of the numerous observations, presenting two possible explanations. Their work is entitled: “An Extremely high-altitude plume seen at Mars morning terminator.”

Map from the Mars Global Surveyor of the current magnetic fields on Mars. Credit: NASA/JPL
Map from the Mars Global Surveyor of the current magnetic fields on Mars. Credit: NASA/JPL

The phenomena occurred over the Terra Cimmeria region centered at 45 degree south latitude. This area includes the tiger stripe array of magnetic fields emanating from concentrations of ferrous (iron) ore deposits on Mars; discovered by the Mars Global Surveyor magnetometer during low altitude aerobraking maneuvers at the beginning of the mission in 1998. Auroral events have been observed over this area from the interaction of the Martian magnetic field with streams of energetic particles streaming from the Sun. Sánchez-Lavega states that if these plumes are auroras, they would have to be over 1000 times brighter than those observed over the Earth.

Auroras photographed from The International Space Station. The distinct Manicouagan impact crater is seen in northern Canada. Terrestial aurora exist at altitudes of 100 km (60 miles) (Credit: NASA)
Auroras photographed from The International Space Station. The distinct Manicouagan impact crater is seen in northern Canada. Terrestial aurora exist at altitudes of 100 km (60 miles) (Credit: NASA)

The researchers also state that another problem with this scenario is the altitude. Auroras over Mars in this region have been observed up to 130 km, only half the height of the features. In the Earth’s field, aurora are confined to ionospheric altitudes – 100 km (60 miles). The Martian atmosphere at 200 km is exceedingly tenuous and the production of persistent and very bright aurora at such an altitude seems highly improbable.

The duration of the plumes – March 12th to 23rd, eleven days (after which observations of the area ended) and April 6th to 16th – is also a problem for this explanation. Auroral arcs on Earth are capable of persisting for hours. The Earth’s magnetic field functions like a capacitor storing charged particles from the Sun and some of these particles are discharged and produced the auroral oval and arcs. Over Mars, there is no equivalent capacitive storage of particles. Auroras over Mars are “WYSIWYG” – what you see is what you get – directly from the Sun. Concentrated solar high energy streams persisting for this long are unheard of.

The second explanation assessed by the astronomers is dust or ice crystals lofted to this high altitude. Again the altitude is the big issue. Martian dust storms will routinely lift dust to 60 km, still only one-third the height of the plumes. Martian dust devils will lift particles to 20 km. However, it is this second explanation involving ice crystals – Carbon Dioxide and Water – that the researchers give the most credence. In either instance, the particles must be concentrated and their reflectivity must account for the total brightness of the plumes. Ice crystals would be more easily transported to these heights, and also would be most highly reflective.

The paper also considered the shape of the plumes. The remarkable quality of modern amateur astrophotography cannot be overemphasized. Also the duration of the plumes was considered. By local noon and thereafter they were not observed. Again, the capabilities tendered by ground-based observations were unique and could not be duplicated by the present set of instruments orbiting Mars.

A Martian dust devil roughly 12 miles (20 kilometers) high was captured on Amazonis Planitia region of Mars, March 14, 2012 by the HiRISE camera on NASA's Mars Reconnaissance Orbiter. The plume is little more than three-quarters of a football field wide (70 yards, or 70 meters). (Image credit: NASA/JPL-Caltech/UA)
A Martian dust devil roughly 12 miles (20 kilometers) high was captured on Amazonis Planitia region of Mars, March 14, 2012 by the HiRISE camera on NASA’s Mars Reconnaissance Orbiter. The plume is little more than three-quarters of a football field wide (70 yards, or 70 meters). (Image credit: NASA/JPL-Caltech/UA)

Still too many questions remain and the researchers state that “both explanations defy our present understanding of the Mars’ upper atmosphere.” By March 20th and 21st, the researchers summarized that at least 18 amateur astronomers observed the plume using from 20 to 40 cm telescopes (8 to 16 inch diameter) at wavelengths from blue to red. At Mars, the Mars Color Imager on MRO (MARCI) could not detect the event due to the 2 hour periodic scans that are compiled to make global images.

Of the many ground observations, the researchers utilized two sets from the venerable astrophotographers Don Parker and Daiman Peach. While observations and measurements were limited, the researchers analysis was exhaustive and included modeling assuming CO2, Water and dust particles. The researchers did find a Hubble observation from 1997 that compared favorably with the 2012 events and likewise modeled that event for comparison. However, Hubble results provided a single observation and the height estimate could not be narrowly constrained.

Explanation of these events in 2012 are left open-ended by the research paper. Additional observations are clearly necessary. With increased interest from amateurs and continued quality improvements plus the addition of the Maven spacecraft suite of instruments plus India’s Mars Orbiter mission, observations will eventually be gained and a Martian mystery solved to make way for yet another.

References:

An Extremely High-Altitude Plume seen at Mars’ Morning Terminator, Journal Nature, February 16, 2015

Amateur astronomer photographs curious cloud on Mars, AstroBob, March 22, 2012

Weather Forecasting on Mars Likely to be Trickier Than on Earth

Predicting the weather here on Earth is never an easy thing, but predicting it on Mars may be ever trickier. Such is the argument presented by a recent study concerning “macroweather” patterns on the Red Planet, a new regime for understanding how planetary environments work.

When it comes to describing the climate of a planet, two important concepts come into play. First, there’s weather, which covers day-to-day changes due to fluctuations in the atmosphere. Second, there’s climate, which is more stable and subject to change over the course of decades. Macroweather, the latest addition to the game, describes the relatively stable periods that exist between short-term weather and long-term climate.

For those of us dwelling here on planet Earth, these are familiar concepts. But researchers say this same three-part pattern applies to atmospheric conditions on Mars. The results of a new paper, published today in Geophysical Research Letters also show that the Sun plays a major role in determining macroweather.

Several dust devils cross a plain in this animation of a series of images acquired by NASA's Mars Rover Spirit in May, 2005. (NASA/JPL-Caltech/Cornell/USGS)
Several dust devils cross a plain in this animation of a series of images acquired by NASA’s Mars Rover Spirit in May, 2005. (NASA/JPL-Caltech/Cornell/USGS)

The scientists chose to study Mars because of the wealth of data it has provided in recent decades, which they then used to test their theory that a transitional “macroweather” regime exists on a planet other than Earth. They used information collected from the Viking Mars lander mission from the 1970s and 1980s, and more recent data from the Mars Global Surveyor.

By taking into account how the sun heats Mars, as well as the thickness of the planet’s atmosphere, the scientists predicted that temperatures and wind would fluctuate on Mars similar to how they fluctuate on Earth. However, this transition from weather to macroweather would take place over 1.8 Martian days (about two Earth days), compared with a week to 10 days here on Earth.

“Our analysis of the data from Mars confirmed this prediction quite accurately,” said Shaun Lovejoy, a physics professor at McGill University in Montreal, Canada, and lead author of the paper. “This adds to evidence, from studies of Earth’s atmosphere and oceans, that the sun plays a central role in shaping the transition from short-term weather fluctuations to macroweather.”

Early Spring Dust Storms at the North Pole of Mars. Early spring typically brings dust storms to northern polar Mars. As the north polar cap begins to thaw, the temperature difference between the cold frost region and recently thawed surface results in swirling winds. The choppy dust clouds of several dust storms are visible in this mosaic of images taken by the Mars Global Surveyor spacecraft in 2002. The white polar cap is frozen carbon dioxide. (NASA/JPL/Malin Space Science Systems)
Early Spring Dust Storms at the North Pole of Mars, taken by the Mars Global Surveyor spacecraft in 2002. Image Credit: NASA/JPL/Malin Space Science Systems

The findings also indicate that weather on Mars can be predicted with some skill only two days in advance, compared to 10 days on Earth.

“We’re going to have a very hard time predicting the weather on Mars beyond two days given what we have found in weather records there,” said co-author Jan-Peter Muller from the University College London Mullard Space Science Laboratory in the UK, “which could prove tricky for the European lander and rover.”

This research promises to advance scientists’ understanding of the dynamics of Earth’s own atmosphere, and could potentially provide insights into the weather of Venus, Saturn’s moon Titan, and possibly the gas giants Jupiter, Saturn, Uranus, and Neptune.

As always, in learning about other planets and their climates, scientists are finding that the planets of our Solar System may have more in common with Earth than previously thought. Because of this, studying these other worlds will inevitably help us to better understand our own.

Further Reading: AGU, McGill

For Valentine’s Day, Enjoy These Hearts On Earth, Mars And Other Places

While we’re unsure about the status of chocolates and flowers in locations far beyond Earth, there certainly is no lack of hearts for us to look at to enjoy Valentine’s Day. If you look at enough geologic features or gas clouds, statistically some of them will take on shapes that we recognize (such as faces).

Below, we’ve collected some hearts on Mars and other places in the universe. Have we missed any? Share other astronomy hearts in the comments!

This heart-shaped feature on Mars "is actually a pit formed by collapse within a straight-walled trough known in geological terms as a graben," wrote Malin Space Systems in 1999. Picture taken by Mars Global Surveyor. Credit: Malin Space Science Systems, MGS, JPL, NASA
This heart-shaped feature on Mars “is actually a pit formed by collapse within a straight-walled trough known in geological terms as a graben,” wrote Malin Space Systems in 1999. Picture taken by Mars Global Surveyor. Credit: Malin Space Science Systems, MGS, JPL, NASA
A heart-shaped mesa captured by Mars Global Surveyor in 1999, in the Promethei Rupes region. Credit: Malin Space Science Systems, MGS, JPL, NASA
A heart-shaped mesa captured by Mars Global Surveyor in 1999, in the Promethei Rupes region. Credit: Malin Space Science Systems, MGS, JPL, NASA
The Heart and Soul nebulae in an infrared mosaic from NASA's Wide-field Infrared Survey Explorer (WISE). It is located about about 6,000 light-years from Earth. Credit: NASA/JPL-Caltech/UCLA
The Heart and Soul nebulae in an infrared mosaic from NASA’s Wide-field Infrared Survey Explorer (WISE). It is located about about 6,000 light-years from Earth. Credit: NASA/JPL-Caltech/UCLA

 

 

 

From Mars with Love on Valentines Day

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Happy Valentine’s Day from Mars to all the readers of Universe Today !

Well it’s truly a solar system wide Valentines celebration. From the Moon, Mars and even Comet Temple 1 with some pixie Stardust for the romantic rendezvous upcoming in a few short hours [Stardust-NExT Flyby at 11:37 p.m. EST Feb 14].

The Martian camera team from Malin Space Systems, San Diego, wishes to share a special heart-shaped feature from Arabia Terra – images above and below – with all Mars fans on this St. Valentine’s Day, Feb. 14, 2011. And certainly, I love Mars ! Especially those gorgeous and brainy twin gals Spirit & Opportunity.

Heart-shaped feature in Arabia Terra on Mars at 21.9 degrees north latitude, 12.7 degrees west longitude. Credit: NASA/JPL-Caltech/MSSS.
The image was taken on May 23, 2010 – at the start of northern summer on Mars – by the Malin-built and operated Context Camera on NASA’s Mars Reconnaissance Orbiter.

The bright heart shaped feature is about 1 kilometer (0.6 mile) long. Arabia Terra lies in the northern hemisphere of Mars

The tip of the heart lies above a small impact crater centered at 21.9 degrees north latitude, 12.7 degrees west longitude.

According to a JPL press release, “The crater is responsible for the formation of the bright, heart-shaped feature. When the impact occurred, darker material on the surface was blown away, and brighter material beneath it was revealed.

PIA13799: Heart-Shaped Feature in Arabia Terra (Wide View). Credit: NASA/JPL-Caltech/MSSS.
Some of this brighter material appears to have flowed further downslope to form the heart shape, as the small impact occurred on the blanket of material ejected from a much larger impact crater.

The Jet Propulsion Laboratory, Pasadena, Calif manages MRO for NASA.

More Martian hearts images below from another Malin built camera aboard NASA’s Mars Global Surveyor orbiter

Happy Valentines Day from Mars Global Surveyor (MGS)
This heart shaped pit on Mars is located on the east flank of the Alba Patera volcano in northern Tharsis. The pit was formed by collapse within a straight-walled trough known in geological terms as a graben. Graben are formed along fault lines by expansion of the bedrock terrain. Credit: NASA/JPL-Caltech/MSSS.
10 Martian Hearts for Valentine’s Day.
Mesas and depressions from all across Mars. Images taken by Mars Global Surveyor from 2001 to 2004. Credit: NASA/JPL-Caltech/MSSS.
Heart shaped landforms on Mars – or perhaps a box of chocolates !
Image taken by Mars Global Surveyor. Credit: NASA/JPL-Caltech/MSSS

Carbon Dioxide — Not Water — Creating Gullies on Mars, New Study Says

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Intriguing images of brand new, fresh gullies on Mars has most of us thinking of one thing: water. But at least for one type of Mars gully, carbon dioxide frost is the impetus behind fresh flows showing up on images from orbiting spacecraft.

“Gullies that look like this on Earth are caused by flowing water, but Mars is a different planet with its own mysteries,” said Serina Diniega, author of a new paper published in the journal Geology. “The timing we see points to carbon dioxide, and if the mechanism is linked to carbon-dioxide frost at these dune gullies, the same could be true for other gullies on Mars.”

Scientists have seen evidence of fresh gullies on Mars, beginning 2000 with images from the Mars Global Surveyor. Different mechanisms were proposed including water and carbon dioxide, as well as other forces.

On the HiRISE website, searching for “gullies” provides a bounty of images. Some fresh gullies are on sand dunes, commonly starting at a crest. Others are on rockier slopes, such as the inner walls of craters, sometimes starting partway down the slope.

Active Dune Gullies in Kaiser Crater (ESP_018186_1330) Active Dune Gullies in Kaiser Crater. Credit: NASA/JPL/University of Arizona

While a graduate student at the University of Arizona, Tucson, Diniega tracked changes in gullies on faces of sand dunes in seven locations on southern Mars. In looking at before-and-after images, in all cases, the gullies appeared after the known winter build-up of carbon-dioxide frost on the dunes. Before-and-after images that looked at periods in spring, summer and autumn showed no new activity.

Because new flows in these gullies apparently occured in winter, rather than at a time when any frozen water might be most likely to melt, Diniega and co-authors at the University of Arizona and Johns Hopkins University Applied Physics Laboratory believe they found evidence that carbon dioxide, rather than water, were responsible for the flows. Some carbon dioxide from the Martian atmosphere freezes on the ground during winter and sublimates back to gaseous form as spring approaches.

A series of images from HiRISE taken from 2008 to 2010 showing changes in a gully. Credit: NASA/JPL/University of Arizona

“One possibility is that a pile of carbon-dioxide frost accumulating on a dune gets thick enough to avalanche down and drag other material with it,” Diniega said. Other suggested mechanisms are that gas from sublimating frost could lubricate a flow of dry sand or erupt in puffs energetic enough to trigger slides.

The team focused their study on dune gullies that are shaped like rockier slope gullies, with an alcove at the top, a channel or multiple channels in the middle, and an apron at the bottom. The 18 dune gullies in which the researchers observed new activity range in size from about 50 meters or yards long to more than 3 kilometers (2 miles) long.

Source: JPL

Mars Methane Gets Even More Mysterious

Mars’ atmosphere consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains small amounts of oxygen and water, as well as trace amounts of methane. The methane – although small in percentage – might be the most intriguing because the source of this very short-lived gas remains a mystery. And the mystery has just gotten a little more puzzling, as the lifetime of methane in Mars atmosphere appears to be even shorter than scientists had originally thought. Using observations from the Mars Global Surveyor — which functioned in orbit around for almost ten years – a group of scientists from Italy have determined the methane in the atmosphere of Mars lasts less than a year.

Scientists Sergio Fonti (Università del Salento) and Giuseppe Marzo (NASA Ames) reported their findings of evolution of the methane over three Martian years at the European Planetary Science Congress in Rome.

“Only small amounts of methane are present in the Martian atmosphere, coming from very localized sources,” said Fonti. “ We’ve looked at changes in concentrations of the gas and found that there are seasonal and also annual variations. The source of the methane could be geological activity or it could be biological – we can’t tell at this point. However, it appears that the upper limit for methane lifetime is less than a year in the Martian atmosphere.”

Levels of methane are highest in autumn in the northern hemisphere, with localized peaks of 70 parts per billion, although methane can be detected across most of the planet at this time of year. There is a sharp decrease in winter, with only a faint band between 40-50 degrees north. Concentrations start to build again in spring and rise more rapidly in summer, spreading across the planet.

“One of the interesting things that we’ve found is that in summer, although the general distribution pattern is much the same as in autumn, there are actually higher levels of methane in the southern hemisphere. This could be because of the natural circulation occurring in the atmosphere, but has to be confirmed by appropriate computer simulations,” said Fonti.

Top: Map of methane concentrations in Autumn (first martian year observed). Peak emissions fall over Tharsis (home to the Solar System's largest volcano, Olympus Mons), the Arabia Terrae plains and the Elysium region, also the site of volcanos. Bottom: True colour map of Mars. Credit: NASA/Università del Salento

There are three regions in the northern hemisphere where methane concentrations are systematically higher: Tharsis and Elysium, the two main volcano provinces, and Arabia Terrae, which has high levels of underground water ice. Levels are highest over Tharsis, where geological processes, including magmatism, hydrothermal and geothermal activity could be ongoing.

“It’s evident that the highest concentrations are associated with the warmest seasons and locations where there are favorable geological – and hence biological – conditions such as geothermal activity and strong hydration. The higher energy available in summer could trigger the release of gases from geological processes or outbreaks of biological activity,” said Fonti.

The mechanisms for removing methane from the atmosphere are also not clear. Photochemical processes would not break down the gas quickly enough to match observations. However, wind driven processes can add strong oxidisers to the atmosphere, such as the highly reactive salt perchlorate, which could soak up methane much more rapidly.

Martian years are nearly twice as long as Earth years. The team used observations from the Thermal Emission Spectrometer (TES) on Mars Global Surveyor between July 1999 and October 2004. The team studied one of the characteristic spectral features of methane in nearly 3 million TES observations, averaging data together to eliminate noise.

“Our study is the first time that data from an orbiting spectrometer has been used to monitor methane over an extended period, “ Fonti said. “The huge TES dataset has allowed us to follow the methane cycle in the Martian atmosphere with unprecedented accuracy and completeness. Our observations will be very useful in constraining the origins and significance of Martian methane.”

Methane was first detected in the Martian atmosphere by ground based telescopes in 2003 and confirmed a year later by ESA’s Mars Express spacecraft. Last year, observations using ground based telescopes showed the first evidence of a seasonal cycle.

Source: European Planetary Science Congress

New Theory Says Phobos Formed From Re-Accretion of Impact Debris

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Most theories on the formation of Phobos and its sister moon of Mars, Deimos, hold that the two moons did not form along with Mars, but were captured asteroids. However, new research indicates that Phobos formed relatively near its current location via re-accretion of material blasted into Mars’ orbit by some catastrophic event, such as a huge impact. This could be an event similar to how Earth’s moon formed. Thermal infrared spectra data from two Mars missions, ESA’s Mars Express and NASA’s Mars Global Surveyor have provided independent researchers similar new conclusions of how Phobos formed.

The origin of the two Martian satellites has been a long standing puzzle. Previous researchers have postulated that because of Phobos small size and highly cratered surface, as well as the fact that Mars is reasonably close to the asteroid belt, that Phobos was a captured asteroid. Recently, alternative scenarios suggested that both moons were formed in-situ by the re-accretion of rocky-debris blasted into Mars’s orbit after a large impact or by re-accretion of remnants of a former moon which was destroyed by Mars’s tidal force.

Today, Dr. Giuranna from the Istituto Nazionale di Astrofisica in Rome, Italy, and Dr. Rosenblatt from the Royal Observatory of Belgium presented their new findings at the European Planetary Science Congress in Rome, saying that the thermal data from the two spacecract, as well as the measurements of Phobos’ high porosity from the Mars Radio Science Experiment (MaRS) on board Mars Express, supports the re-accretion scenario.

“Understanding the composition of the Martian moons is the key to constrain these formation theories,” said Giuranna.

Spatial locations of TES and observations of Phobos used for the compositional analysis. Credit: Giuranna and Rosenblatt

Previous observations of Phobos at visible and near-infrared wavelengths suggest the possible presence of carbonaceous chondritic meteorites, carbon-rich and likely from the early formation of the solar system, commonly associated with asteroids dominant in the middle part of the asteroid belt. This finding would support the early asteroid capture scenario. However recent thermal infrared observations from the Mars Express Planetary Fourier Spectrometer, show poor agreement with any class of chondritic meteorite. They instead argue in favor of the in-situ scenarios.

“We detected for the first time a type of mineral called phyllosilicates on the surface of Phobos, particularly in the areas northeast of Stickney, its largest impact crater,” said Giuranna. “This is very intriguing as it implies the interaction of silicate materials with liquid water on the parent body prior to incorporation into Phobos. Alternatively phyllosilicates may have formed in situ, but this would mean that Phobos required sufficient internal heating to enable liquid water to remain stable. More detailed mapping, in-situ measurements froma lander, or sample return would ideally help to settle this issue unambiguously.”

But other observations appear to match up with the types of minerals identified on the surface of Mars. From that data, Phobos appears more closely related to Mars than objects from other locations in the solar system.

“The asteroid capture scenarios also have difficulties in explaining the current near-circular and near-equatorial orbit of both Martian moons,” said Rosenblatt.

The MaRS instrument used the frequency variations of the radio-link between the spacecraft and the Earth-based tracking stations in order to precisely reconstruct the motion of the spacecraft when it is perturbed by the gravitational attraction of Phobos, and from this, the team was able provide most precise measurement of Phobos’ mass, with a precision of 0.3%.

Additionally, the team was able to give the best estimate yet of Phobos’s volume, with a density of 1.86±0.02 g/cm3.

“This number is significantly lower than the density of meteoritic material associated with asteroids. It implies a sponge-like structure with voids making up 25-45% in Phobos’ interior,” said Rosenblatt.

“High porosity is required in order to absorb the energy of the large impact that generated Stickney crater (the large crater on Phobos) without destroying the body,, said Giuranna. “In addition a highly porous interior of Phobos, as proposed by the MaRS team, supports the re-accretion formation scenarios”.

The researchers said a highly porous asteroid would have probably not survived if captured by Mars. Alternatively, such a highly porous Phobos can result from the re-accretion of rocky-blocks in Mars’ orbit. During re-accretion, the largest blocks re-accrete first because of their larger mass, forming a core with large boulders. Then, the smaller debris re-accrete but do not fill the gaps left between the large blocks because of the low self-gravity of the small body in formation. Finally, a relatively smooth surface masks the space of voids inside the body, which then can only be indirectly detected. Thus, a highly porous interior of Phobos, as proposed by the MaRS team, supports the re-accretion formation scenarios.

The researchers said they would like more data on Phobos to verify their findings, and the upcoming Russian Phobos-Grunt mission (Phobos Sample Return), scheduled for launch in 2011, will help to provide more understanding regarding the origin of Phobos.

Source: Europlanet Conference

Mars Global Surveyor

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The Mars Global Surveyor was a spacecraft sent to Mars in 1996. It arrived at Mars and studied the planet for 10 years, until it broke down in 2006, and controllers on Earth lost contact with it. But while it was operating, the spacecraft took thousands of images, and made some major discoveries about Mars.

Mars Global Surveyor was launched on November 7, 1996, and made its orbital insertion on September 11, 1997. It used a technique called aerobraking to reduce its orbit and bring it into an orbit that brought it to an average distance of 378 km from the surface of Mars. It circled the planet in a polar orbit once every 117 minutes, which allowed it to photograph the entire Martian surface.

The spacecraft was equipped with 5 major scientific instruments: Mars Orbiter Camera, Mars Orbiter Laser Altimeter, Thermal Emission Spectrometer, Magnetometer and electron reflectometer and the Ultrastable Oscillator for Doppler measurements. These instruments allowed the spacecraft to study the atmosphere and surface composition of Mars. But it also sent back the highest resolution photographs ever seen of Mars. The newer Mars Reconnaissance Orbiter has returned better images with its larger telescope, but when the first MGS images first came back from Mars, they were stunning.

It made some incredible discoveries about Mars. Thanks to the observations from MGS, astronomers determined that Mars had a layered crust that was more than 10 km thick. It found ancient craters that had been buried and then later exposed by erosion, and it found evidence of ancient lava flows.

But perhaps the biggest discovery was made in 2006, which researchers announced that they had uncovered evidence of recent water activity on Mars. Images from the Mars Global Surveyor showed gullies on Mars which looked like they’d been formed by water. It’s possible that water had erupted out of an underground aquifer and spilled down the slope of a hill before evaporating in the pressure of the Martian atmosphere.

After a decade of service, Mars Global Surveyor went silent on November 2, 2006. It went into safe mode after being issued commands to change the orientation of its solar panels, and it stopped communicating. NASA said that it was, “battery failure caused by a complex sequence of events involving the onboard computer memory and ground commands.” But we’ll never really know what happened to it.

We’ve written many articles about the Mars Global Surveyor for Universe Today. Here’s an article about how we lost contact with the Mars Global Surveyor, and here’s a picture of Earth taken by MGS.

If you’d like more info, check out the Mars Global Surveyor homepage.

Source: NASA