This volcanic cone in the Nili Patera caldera on Mars has hydrothermal mineral deposits on the southern flanks and nearby terrains. Two of the largest deposits are marked by arrows, and the entire field of light-toned material on the left of the cone is hydrothermal deposits. Image Credit: NASA/JPL-Caltech/MSSS/JHU-APL/Brown Univ.
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Evidence of a past “hot spring” environment on Mars has shown up in images from the Mars Reconnaissance Orbiter. Scientists say light-colored mounds of hydrated silica on the side of a volcano are likely deposits from steam fumaroles, or hot springs, which may have provided a habitable environment on the Red Planet about three billion years ago. Concentrations of hydrated silica have been identified on Mars previously, including an ancient hot springs environment that the Spirit rover stumbled across in 2007.
“The heat and water required to create this deposit probably made this a habitable zone,” said J.R. Skok from Brown University, lead author of a paper about these findings published online today by Nature Geoscience. “If life did exist there, this would be a promising type of deposit to entomb evidence of it — a microbial mortuary.”
While it is not direct evidence of life on Mars, it adds to the mounting evidence of past habitable environments for at least microbial life on the planet, and is the most intact ancient hot springs region ever found. This specific spot in the Syrtis Major volcanic region on Mars would have been hospitable to life when most of Mars was already dry and cold.
Skok said, “You have spectacular context for this deposit. It’s right on the flank of a volcano. The setting remains essentially the same as it was when the silica was deposited.”
The small cone rises about 100 meters (100 yards) from the floor of a shallow volcanic caldera named Nili Patera and covers about 50 kilometers (30 miles) of Syrtis Major, which is near Mars equator. The collapse of an underground magma chamber from which lava had emanated created the bowl, and subsequent lave flows tell a story of how the cone formed.
“We can read a series of chapters in this history book and know that the cone grew from the last gasp of a giant volcanic system,” said John Mustard, Skok’s thesis advisor at Brown and a co-author of the paper. “The cooling and solidification of most of the magma concentrated its silica and water content.”
Orbital images revealed patches of bright deposits near the summit of the cone, fanning down its flank, and on flatter ground in the vicinity. The Brown researchers partnered with Scott Murchie of Johns Hopkins University Applied Physics Laboratory, Laurel, Md., to analyze the bright exposures with the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the orbiter.
Silica can be dissolved, transported and concentrated by hot water or steam. Hydrated silica identified by the spectrometer in uphill locations — confirmed by stereo imaging — indicates that hot springs or fumaroles fed by underground heating created these deposits. Silica deposits around hydrothermal vents in Iceland are among the best parallels on Earth.
Murchie said, “The habitable zone would have been within and alongside the conduits carrying the heated water.” The volcanic activity that built the cone in Nili Patera appears to have happened more recently than the 3.7-billion-year or greater age of Mars’ potentially habitable early wet environments recorded in clay minerals identified from orbit.
Gullies on a Martian sand dune in this trio of images from NASA's Mars Reconnaissance Orbiter deceptively resemble features on Earth that are carved by streams of water. However, these gullies likely owe their existence to entirely different geological processes apparently related to the winter buildup of carbon-dioxide frost. Image Credit: NASA/JPL-Caltech/University of Arizona
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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.
A mosaic of images shows the soil in front of the Mars Exploration Rover Spirit. Bright-toned soil was freshly exposed by the rover's left-front wheel. The inset show a magnified view of the nearby rectangles within the mosaic, showing the differences between undisturbed and disturbed soil. Credit: NASA/JPL-Caltech/Cornell University
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She may be down, but she’s not out – out of the discovery department, anyway. Data from the Spirit Mars rover – currently in hibernation – shows evidence that water, perhaps as snow melt, trickled into the subsurface fairly recently and may be doing so on a continuing basis.
The area where Spirit became stuck in sandy soil in April of 2009 was churned up by her spinning wheels as engineers at the Jet Propulsion Laboratory attempted to drive her out of a veritable sand trap. This wheel-churning brought subsurface soil layers — which include the water soluble mineral ferric sulfate — up to the surface. Under a thin covering of windblown sand and dust, relatively insoluble minerals such as hematite, silica and gypsum are concentrated near the surface and more-soluble ferric sulfates have higher concentrations below that layer. This pattern suggests water has moved downward through the soil, dissolving and carrying the ferric sulfates.
The deputy principal investigator for the Spirit and Opportunity rover, Ray Arvidson and his team say that thin films of water may have entered the ground from frost or snow. (The Phoenix lander saw evidence of current snowfall.) The seepage could have happened during cyclical climate changes in periods when Mars tilted farther on its axis.
“The lack of exposures at the surface indicates the preferential dissolution of ferric sulfates must be a relatively recent and ongoing process since wind has been systematically stripping soil and altering landscapes in the region Spirit has been examining,” said Arvidson.
This isn’t the first time that Spirit’s wheels have churned up interesting stuff. Back in 2008, researchers said Spirit’s bum front wheel uncovered signs minerals that are found in hot springs, similar to what is at Yellowstone National Park on Earth, and similar hot springs may have once bubbled or steamed on Mars.
But there’s been no word from the rover since March 22, 2010, after she went into cold-induced hibernation. Because Spirit was stuck, the rover drivers could not get her in the best position to receive maximum sunlight.
“With insufficient solar energy during the winter, Spirit goes into a deep-sleep hibernation mode where all rover systems are turned off, including the radio and survival heaters,” said John Callas, project manager for Spirit and Opportunity. “All available solar array energy goes into charging the batteries and keeping the mission clock running.”
While she was stuck and still awake, researchers took advantage and examined in great detail soil layers the wheels had exposed, and also neighboring surfaces, making comparisons between the two. While trying to drive back out of her predicament, Spirit made 13 inches of progress in its last 10 backward drives before energy levels fell too low. Those drives exposed a new area of soil for possible examination if Spirit does awaken and if its robotic arm is still usable.
However, it is thought that the aging Spirit rover experienced the coldest temperatures ever, and it may not survive. Everyone is still holding out hope that the rover may yet make contact through one of the orbiting spacecraft and the Deep Space Network.
If Spirit does get back to work, the top priority is a multi-month study that can be done without driving the rover. The study would measure the rotation of Mars through the Doppler signature of the stationary rover’s radio signal with enough precision to gain new information about the planet’s core.
Meanwhile, over on the other side of Mars, the rover Opportunity has been making steady progress toward a large crater, Endeavour, which is now approximately 8 kilometers (5 miles) away.
Artist's impression of water under the Martian surface. If underground aquifers really do exist, the implications for human exploration and eventual colonization of the red planet would be far-reaching. (Illustration: ESA)
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Images from the spacecraft orbiting Mars seem to indicate the Red Planet may once have had oceans and lakes, and researchers are still trying to figure out how these bodies of water could have developed. A new explanation is that underground aquifers fed water to the surface, forming the floors of ancient continental-scale basins on Mars. The groundwater emerged through extensive and widespread fractures, leading to the formation of river systems, large-scale regional erosion, sedimentary deposition and water ponding in widespread and long-lasting bodies of water in Mars northern plains.
J. Alexis Palmero Rodriguez, research scientist at the Planetary Science Institute PSI, has been studying the Martian northern lowlands region, finding extensive sedimentary deposits that resemble the abyssal plains of Earth’s ocean floors. It is also like the floors of other basins on Mars where oceans are thought to have developed.
The origin of these deposits and the formation of Martian lakes and seas has been a controversial subject over the years. One theory is that there was a sudden release of large volumes of water and sediment from zones of apparent crustal collapse known as “chaotic terrains.” However, these zones of collapse are on the whole rare on Mars, while the plains deposits are widespread and common within large basin settings, Rodriguez said.
From evidence in the planet’s northern plains (south of Gemini Scopuli in Planum Boreum), Rodriguez’ new model does not require sudden massive groundwater discharges. Instead, it advocates for groundwater discharges being widespread, long-lived and common in the northern plains of Mars.
Large gully on Mars, seen by the Mars Reconnaissance Orbiter's HiRISE camera. Credit: NASA/JPL/University of Arizona
“With the loss over time of water from the subsurface aquifer, areas of the northern plains ultimately collapsed, creating the rough hilly surfaces we see today. Some plateaus may have avoided this fate and preserved sedimentary plains containing an immense record of hydrologic activity,” Rodriguez said. “The geologic record in the collapsed hilly regions would have been jumbled and largely lost.
“This model implies that groundwater discharges within basin settings on Mars may have been frequent and led to formation of mud pools, lakes and oceans. In addition, our model indicates this could have happened at any point in the planet’s history,” he said. “There could have been many oceans on Mars over time.”
If life existed in Martian underground systems, life forms could have been brought up to the surface via the discharges of these deep-seated fluids. Organisms and their fossils may therefore be preserved within some of these sedimentary strata, Rodriguez said.
Possible Phyllosilicate-Rich Area in Syrtis Major. Credit: NASA/JPL/University of Arizona
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Data from the Mars Reconnaissance Orbiter suggests that there could be habitable environments underground on Mars – in the past, and perhaps even today. Scientists discovered evidence of long-sought-after hydrothermally altered carbonate-bearing rocks which were once deep within the Red Planet, exposed within an impact crater. “Carbonate rocks have long been a Holy Grail of Mars exploration for several reasons,” said Joseph Michalski from the Planetary Science Institute. He explained that on Earth, carbonates form with the ocean and within lakes, so the same could be true for ancient Mars. “Such deposits could indicate past seas that were once present on Mars. Another reason is because we suspect that the ancient Martian atmosphere was probably denser and CO2-rich, but today the atmosphere is quite thin so we infer that the CO2 must have gone into carbonate rocks somewhere on Mars.”
This unique mineralogy was spotted within the central peak of a crater to the southwest of a giant Martian volcanic province named Syrtis Major. With infrared spectra from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), planetary geologists detected the hydrothermal minerals from their spectroscopic fingerprints. Visible images from the HiRISE camera (High Resolution Imaging Science Experiment) on board MRO show that the carbonates and hydrated silicate minerals occur within deformed bedrock that was exhumed by an ancient meteor impact that poked through the volcanic upper crust of Mars.
The carbonate-bearing rocks were once likely about 6 km (about 4 miles) underground. The carbonate minerals exist along with hydrated silicate minerals of a likely hydrothermal origin.
Syrtis Major Planum Channel and Depression. Credit: NASA/JPL/University of Arizona
While this is not the first detection of carbonates on Mars, Michalski said, “This detection is significant because it shows other carbonates detected by previous workers, which were found in a fairly limited spatial extent, were not a localized phenomenon. Carbonates may have formed over a very large region of ancient Mars, but been covered up by volcanic flows later in the history of the planet. A very exciting history of water on Mars may be simply covered up by younger lava!”
The discovery also has implications for the habitability of the Martian crust. “The presence of carbonates along with hydrothermal silicate minerals indicates that a hydrothermal system existed in the presence of CO2 deep in the Martian crust,” Michalski says. “Such an environment is chemically similar to the type of hydrothermal systems that exist within the ocean floor of Earth, which are capable of sustaining vast communities of organisms that have never seen the light of day.
“The cold, dry surface of Mars is a tough place to survive, even for microbes. If we can identify places where habitable environments once existed at depth, protected from the harsh surface environment, it is a big step forward for astrobiological exploration of the red planet.”
Michalski and co-author Paul B. Niles of NASA Johnson Space Center recently published the results in a paper titled “Deep crustal carbonate rocks exposed by meteor impact on Mars” in Nature Geoscience.
Melas Chasma sinks 9 km below the surrounding surface, making it one of the lowest depressions on the planet. Credits: ESA/DLR/FU Berlin (G. Neukum)
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Melas Chasma is part of the huge Valles Marineris that cuts into the middle of Mars surface, making it a pretty interesting place: there is abundant evidence for water having flowed here, with ancient water-cut channels visible even from orbit. Also visible are landslides that have created huge fans of rubble at the base of the cliffs. These newest images from ESA’s Mars Express show Melas Chasma, which sinks 9 km below the surrounding surface, making it one of the lowest depressions on the planet. This is just a small part of the bigger Valles Marineris, which stretches for more than 4,000 km across the surface of Mars. Around Melas Chasma, there are lighter-coloured deposits of sulphate components that were probably deposited in a former lake.
Melas Chasma stretches for more than 4000 km across the face of Mars. Credits: ESA/DLR/FU Berlin (G. Neukum)
An artists illustration of a manned mission to Mars. Credit: NASA
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What will it take to actually get humans to Mars? The best answer is probably money. The right amount of cold, hard cash will certainly solve a lot of problems and eliminate hurdles in sending a human mission to the Red Planet. But cash-strapped federal space agencies aren’t currently in the position to be able to direct a mission to another world – at least in the near term – and seemingly, a trip to Mars is always 20-30 years off into the future. But how about a commercially funded effort?
At first glance, a paper published recently in the somewhat dubious Journal of Cosmology appears to have some merits on using an independent corporation to administer and supervise a marketing campaign – similar to what sports teams do to sell merchandise, gain sponsors, garner broadcasting rights and arrange licensing initiatives. The paper’s author, a psychologist named Dr. Rhawn Joseph, says that going to Mars and establishing a colony would likely cost $150 billion dollars over 10 years, and he lays out a plan for making money for a sustained Mars mission through the sale of merchandise, naming rights and even creating a reality TV show and selling property rights on Mars.
Could such a scheme work?
Not according to former NASA engineer Jim McLane, who has a fairly unique scheme of his own to get humans to Mars: a one-way, one person mission.
For years, McLane has been a proponent of getting humans to Mars as quickly as possible, and his plans for a one-way mission are outlined in a very popular article Universe Today published in 2008. So, what does he think of a commercially funded effort?
Artists impression of a future human mission to Mars. Credit: NASA
“I am a vocal proponent of an early settlement on Mars,” McLane replied to a query from UT, “ So I should have welcomed Dr. Joseph’s proposal to establish a colony in 10 years with private funds and clever marketing. Regrettably, after reading the details of his scheme I believe the good Doctor should stick to peddling his patented herbal sexual dysfunction treatment and refrain from speculating about technologically intensive endeavors like a trip to Mars.”
For starters, McLane wonders about the costs that Joseph proposes. “It’s questionable,” he said. “One cannot propose a cost without first devising a technical approach and he has not done that. He justifies the large investment by alleging that there will be significant financial returns, for example the investors might be able to claim the mineral wealth of the entire planet. However owning such an asset is of dubious value since there is no way to send anything valuable back to Earth.”
Unlike ancient Spanish treasure fleets loaded with silver that sailed every year from the New World, McLane said, nothing on planet Mars will ever be worth the expense of shipping it home. Plus, selling real estate on Mars might not even be a viable option. The 1967 Outer Space Treaty prohibits governments from making extraterrestrial property rights claims, and even though some especially ambitious entrepreneurs have tried selling real estate on the Moon and Mars, ownership of extraterrestrial real estate is not recognized by any authority. According to current space law, any “deed” or claim on another extraterrestrial body has no legal standing.
McLane was also not impressed with Joseph’s statement about the wastefulness of spending on the US military as a justification for spending money on a Mars mission. “It is not as if one program could be substituted for the other,” said McLane. “But, substitution is not what Dr. Joseph proposes. He feels inclined to speculate on the wastefulness of current wars even though this is an essay on Space.”
Some of the ideas Joseph outlined for marketing does have some validity, McLane said. “Long ago NASA should have realized that the image they cultivate of nerdy, ethically and sexually diverse astronauts does not inspire the tax payer nearly as much as the early astronauts who we expected to be risk taking, hell raising test pilots,” he said.
In respect to finances, McLane said he agrees with Joseph that there is a place for private capital, but not in regards to the venture capital proposal.
“Private money could jump start a manned Mars mission,” McLane said, “but persuading billionaires to invest based on some speculative financial return is doomed to fail. I believe rich folks might be willing to help pay to put a human on Mars, but the motivations would be philanthropy and patriotism, not financial gain. Several wealthy citizens might contribute seed money (say a quarter billion dollars or so) to finance a detailed study of the design options for a one way human mission – a concept that thus far NASA refuses to consider. Such a study would reveal the technical practicality of the one-way mission and the relative cheapness of the approach. The study would probably show that a human presence on Mars would cost little more than a human moon base assuming the same 10 year time span for accomplishing both programs.”
Dr. Joseph concludes his paper by asserting that several foreign countries “are already planning on making it to Mars in the next two decades.” McLane said this seems highly improbable since the funds spent today by these nations on manned spaceflight are a tiny fraction of what the US currently spends.
Artist concept of a future human Mars mission. Credit: NASA
While Joseph – and seemingly the current President and NASA leaders favor an international effort to get to Mars, McLane believes this is short-sighted for two reasons.
One, there would be enormous technological returns from a human Mars landing that would greatly stimulate business and the economy. “Why should the US share these large returns with foreign countries,” McLane asked? And second, an all American effort could potentially take advantage of classified US military technology.
McLane did say previously, however, that the world would be excited and unified by a mission to Mars. “The enthusiasm would be the greatest effect of a program that places a man on Mars, over and above anything else, whether it makes jobs, or stimulates the economy, or creates technology spinoffs. We’re all humans and the idea of sending one of our kind on a trip like that would be a wonderful adventure for the entire world. The whole world would get behind it.”
Mars has permanent ice caps at both poles composed mostly of solid carbon dioxide, and mysteriously, a large portion of the northern cap disappears early in the northern Martian spring followed later by its sudden reappearance. Scientists may have solved this mystery, saying that strong winds and Mars’ active water cycle may play a part in ‘come and go’ polar cap.
Earlier this year, another group of scientists from the University of Texas found that so-called katabatic winds — a wind that carries high density air from a higher elevation down a slope under the force of gravity – were responsible for the formation of giant swirls or troughs in the northern polar cap, as well as a huge chasm that is also visible. Those winds may also play a part in the regeneration of the ice cap.
Seasonal ice deposits play a major role in the water cycle of the planet. Every Martian year, alternatively during northern and southern winter, a significant part of the atmosphere condenses on the surface in the form of frost and snow. These seasonal ice deposits, which can be up to one meter thick, are mainly composed of carbon dioxide with minor amounts of water and dust. During spring, the deposits sublimate becoming a substantial source of water vapor, in particular in the northern hemisphere of the planet.
Sudden reappearance of the carbon dioxide ice signature between 'solar longitudes' 59.2 degrees and 60.2 degrees (which corresponds to a time lapse of approximately two Martian days) in the spiral troughs structure of the North polar cap. Credit: ESA
Dr. Bernard Schmitt and Mr. Thomas Appéré analyzed data taken with the OMEGA instrument on board ESA’s Mars Express, honing in on two northern Martian regions. Before the Mars Express mission, scientists monitored the evolution of the seasonal deposits by looking at the albedo (reflectivity) and temperature changes of the surface, as the ice deposits appear much brighter and are colder than the surrounding defrosted terrains.
The first Martian region that the scientists observed is located on Gemina Lingula, a Northern plateau, where a peculiar evolution of the carbon dioxide ice deposits was observed.
“During spring the ice signature disappeared from our data, but the surface temperature was still cold enough to sustain plenty of CO2 ice,” said Schmitt. “We concluded that a thick layer of something else, either dust or water ice was overlaid. If it was dust then it would also hide water ice and the surface of the planet would become darker. None of these happened so we concluded that a layer of water ice was hiding the CO2 ice. We had to wait until the weather gets warm enough on Mars for the water to vaporize as well, and then the carbon dioxide signatures re-appeared in our data.”
Soon after spring sunrise, the solar radiation hitting the surface of Mars warms enough the CO2 ice lying on the top layer to cause it to vaporize. But the water ice needs higher temperatures to sublimate, so a fine grained layer of water ice gradually forms hiding the carbon dioxide ice still lying beneath it.
“A layer only 2 tenths of a millimeter thick is enough to completely hide the CO2 ice. Also some water that has been vaporized at lower, warmer, Martian latitudes condenses as it moves northward and may be cold trapped on top of the CO2 ice,” said Appéré.
The second region analyzed by the team is located in the spiral troughs structure of the North permanent cap. A similar situation was observed but the carbon dioxide ice re-appeared very quickly here after its initial disappearance.
“This hide-and-seek game didn’t make much sense to us. It wasn’t cold enough for CO2 ice to condense again, neither warm enough for water ice to sublimate,” said Schmitt.
(a) Simulation of katabatic (downhill) winds. Colour bar: friction velocity from 0.1 to 0.6 m/s. (b) Localization of regions where early disappearances (blue) and sudden reappearances (orange) of the carbon dioxide ice signature are observed. Credit: ESA
“We concluded that somehow the water ice layer was removed,” said Appéré. “The topography of the North permanent Martian cap is well-suited to entail the formation of strong katabatic winds.”
Another scientist, Dr. Aymeric Spiga, used a model to simulate those winds and he indeed confirmed the sudden re-appearances of CO2 ice where strong katabatic winds blow.
This is just the first step in figuring out exactly how the polar cap disappears and reappears on Mars.
“To decipher the present and past water cycles on Mars and improve our weather models on the planet, one needs to have a good understanding of the seasonal ice deposits dynamics, how they change in space and time,” said Schmitt. “We are confident that our results will make a significant contribution in this direction.”
'Oileán Ruaidh' - the new rock found by the Opportunity rover. It could be another meteorite. Credit: NASA/JPL-Caltech/Cornell University. 3-D by Stuart Atkinson
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The Opportunity rover has done it again — found another strange-looking rock sitting on Meridiani Planum, and it looks like another meteorite. “The dark color, rounded texture and the way it is perched on the surface all make it look like an iron meteorite,” said Matt Golombek from the MER science team. Unofficially named “Oileán Ruaidh” (pronounced ay-lan ruah), which is the Gaelic name (translated: Red Island) for an island off the coast of northwestern Ireland. The rock is about the size of a toaster: 45 centimeters (18 inches) wide from the angle at which it was first seen. Stu Atkinson has posted some enhanced images of the rock on his website, Road to Endeavour, which I have nabbed and posted here. Thanks Stu! The 3-D version above looks awesome with the red/green glasses. And look for more detailed images of the rock on his site soon, as Opportunity comes in for a closer look. UPDATE: As promised, Stu has provided an enhanced close-up of this rock, below.
Close up of a rock on Mars, possibly another meteorite. Credit: NASA/JPL/Cornell, enhanced by Stu Atkinson
Here’s an extreme close-up of Oileán Ruaidh, and it certainly has that “iron meteorite” look about it. It almost looks like the head of a craggy old snapping turtle!
Opportunity's panoramic camera's view of a dark rock that may be an iron meteorite. Image Credit: NASA/JPL-Caltech/Cornell University, enhanced by Stuart Atkinson
Map of methane concentrations in Autumn (first martian year observed) on Mars. Credit: NASA/Università del Salento
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.
