A sample of ther mineral jarosite from a site in Greece. Photo Copyright: Steve Rust
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No. This isn’t an ancient raisin sponge cake you found at the back of your breadbox. It’s a closeup of a rare mineral called jarosite… a hydrated iron sulfate composite which takes on some very specific properties when it is exposed to a wet environment. It was discovered here on Earth in 1852 in ravines in the mountainous coast of southeastern Spain – and it turned up on Mars at a rocky outcropping, dubbed El Capitan, in the crater at Meridiani Planum where Opportunity landed. What makes this ruddy, crystalline structure so exciting is that it can “date” when liquid water may have existed.
If you thought jarosite looked like a left-over, then your assumption is close to correct. It’s actually a byproduct of the weathering of exposed rocks and forms when the right equation of oxygen, iron, sulfur, potassium and water are mixed.
In a recent study published in an October (v. 310) issue of Earth and Planetary Science Letters, Suzanne Baldwin, professor of Earth Sciences in SU’s College of Arts and Sciences; and Joseph Kula, research associate and corresponding author for the study, established the “diffusion parameters” for argon in jarosite. From this, the crystalline structure then produces the noble gas, argon, when certain potassium isotopes in the crystals decay. Like carbon, this potassium decay rate is a radioactive process which has an established rate. By measuring the argon, scientists can then get a close determination on the age when the mineral interacted with liquid water. This bit of information could some day aid scientists in determining Mars’ water history when samples are returned.
“Our experiments indicate that over billion-year timescales and at surface temperatures of 20 degrees Celsius (68 degrees Fahrenheit) or colder, jarosite will preserve the amount of argon that has accumulated since the crystal formed,” Kula says, “which simply means that jarosite is a good marker for measuring the amount of time that has passed since water was present on Mars.”
Since water is critical for most life forms, knowing when, where and how long water might have existed on Mars will help clue us in to potential habitable sites. “Jarosite requires water for its formation, but dry conditions for its preservation,” Baldwin says. “We’d like to know when water formed on the surface of Mars and how long it was there. Studying jarosite may help answer some of these questions.”
But using argon as a “time clock” can still have some potential drawbacks. When exposed to temperature extremes, it is possible for some gas to escape the crystals. To help determine the validity of their hypothesis, the team is currently subjecting jarosite and its argon content to a battery of computer simulations. Fortunately, they have found it to exist over a wide range of conditions – those of which could very well have been a part of Martian history.
“Our results suggest that 4 billion-year-old jarosite will preserve its argon and, along with it, a record of the climate conditions that existed at the time it formed,” Baldwin says. The scientists haven’t stopped their studies yet, and they are conducting further experiments on jarosite that formed less than 50 million years ago in the Big Horn Basin in Wyoming. Through this research they hope to determine the timeline in which the minerals formed and how quickly environmental conditions changed from wet to dry. “The results can be used as a context for interpreting findings on other planets.”
Light-Toned Deposits: This image reveals exposed layers in Noctis Labyrinthus which may contain signatures of iron bearing sulfates and phyllosilcate (clay) minerals. Image Credit: NASA/JPL-Caltech/University of Arizona
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Although it might seem like a fictitious nomenclature, smectite is a real substance and it’s been found on Mars. It’s a clay mineral that, like a sponge, expands and contracts as it takes on liquid water. With magnesium, iron, aluminum and silica in their content, smectites are morphed into being when silicates are exposed to non-acid water. Now Mars has yielded up two such deposits that further indicate the presence of a once wetter world.
“We discovered locations at Noctis Labyrinthus that show many kinds of minerals that formed by water activity,” said Catherine Weitz, lead author and senior scientist at the Planetary Science Institute. “The clays we found, called iron/magnesium (Fe/Mg)-smectites, are much younger at Noctis Labyrinthus relative to those found in the ancient rocks on Mars, which indicates a different water environment in these depressions relative to what was happening elsewhere on Mars.”
Thanks to high-resolution images from the High Resolution Imaging Science Experiment (HiRISE) camera and hyperspectral data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on the Mars Reconnaissance Orbiter (MRO) spacecraft, combined with Digital Terrain Models (DTMs), Weitz and her team observed about 300 meters of escarpment restricted to two 30 to 40 kilometer troughs located at the western edge of the Vallis Marineris canyon. By studying the “geological layers” the team was able to map hydrated minerals and better understand how the water chemistry evolved.
“These clays formed from persistent water in neutral to basic conditions around 2 to 3 billion years ago, indicating these two troughs are unique and could have been a more habitable region on Mars at a time when drier conditions dominated the surface,” said co-author and CRISM team member Janice Bishop from the SETI Institute and NASA AMES Research Center.
The huge troughs reveal a rich geological chronicle of events. Like reading a book, each layer is a chapter in Martian water history. As they would fill, they would take on a chemical signature of that era. Then the troughs would erode and nearby volcanism added its own particular brands. Again, they would fill and chemicals would mix. Even the pH levels of the water adds its own fingerprint to the smectite equation. While it isn’t a unique find, what sets this area apart is that things appear to have happened in a reverse order as opposed to what happened globally across Mars. As exciting as these new finds are, for now studies will have to remain photographic.
“These troughs would be fantastic places to send a rover, but unfortunately the rugged terrain makes it unsafe both for landing and for driving,” Weitz said.
Holden crater is 140 km across, filling the left side of the image, while to the right is the remaining part of Eberswalde crater, with a diameter of about 65 km. They are located in the southern highlands of Mars. North is to the right of the image. The image was acquired by Mars Express at approximately 25°S / 326°E during orbit 7208 on 15 August 2009. The images have a ground resolution of about 22 m per pixel. Credits: ESA/DLR/FU Berlin (G. Neukum)
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In the southern highlands of Mars, Eberswalde crater to be exact, ESA’s Mars Express exploration has pinpointed an area which once held a lake. Although it may have been some 4 billion years ago, the geologic remains – called a delta – are still evident in the new images. This region of dark sediments are a shadowed reminder that Mars once had water.
Formed by an asteroid strike, Eberswalde crater has nearly eroded away with time. After it formed, it was partially obliterated by another impact which shaped 140 km diameter crater Holden. Although this second strike buried Eberswalde with ejecta, 115 square kilometers of delta area and feeder channels survived. These channels once were the arteries that pumped water along the surface to pool in the crater’s interior, forming a lake. As they carried water, they also carried sediments and – just as on Earth – left their mark. With time, the water dried up and even more sediments were carried along by the wind, exposing the area in vivid relief.
NASA’s Mars Global Surveyor spacecraft spied the delta in earlier missions, giving even further solidification that Mars was once a wet world. While Eberswalde crater and Holden crater were once a part of a list of possible landing sites for the Mars Science Laboratory, Gale crater was selected as the Curiosity’s landing site, given its high mineral and structural diversity related to water. But don’t count this wonderful, wet confession of a lake out forever. Thanks to high mineral diversity and suggestive structure, we’re sure to visit the delta of Eberswalde and Holden again, from orbit or with another landing mission.
Opportunity investigates Tisdale 2 rock showing indications of ancient Martian water flow. NASA's Mars Exploration Rover Opportunity used its front hazard-avoidance camera to take this picture showing the rover's arm extended toward a light-toned rock, "Tisdale 2," during Sol 2695 of the rover's work on Mars (Aug. 23, 2011). The composition of Tisdale 2 is unlike any rock studied by Opportunity since landing 7.5 years ago. It is about 12 inches (30 centimeters) tall. Credit: NASA/JPL-Caltech
Scientists directing NASA’s Mars Opportunity rover gushed with excitement as they announced that the aging robot has discovered a rock with a composition unlike anything previously explored on the Red Planet’s surface – since she landed on the exotic Martian plains 7.5 years ago – and which offers indications that liquid water might have percolated or flowed at this spot billions of years ago.
Barely three weeks ago Opportunity arrived at the rim of the gigantic 14 mile ( 22 km) wide crater named Endeavour after an epic multi-year trek, and for the team it’s literally been like a 2nd landing on Mars – and the equivalent of the birth of a whole new mission of exploration at an entirely ‘new’ landing site.
“This is like having a brand new landing site for our veteran rover,” said Dave Lavery, program executive for NASA’s Mars Exploration Rovers at NASA Headquarters in Washington. “It is a remarkable bonus that comes from being able to rove on Mars with well-built hardware that lasts.”
Opportunity has traversed an incredible distance of 20.8 miles (33.5 km) across the Meridiani Planum region of Mars since landing on January 24, 2004 for a 3 month mission – now 30 times longer than the original warranty.
“Tisdale 2” is the name of the first rock that Opportunity drove to and investigated after reaching Endeavour crater and climbing up the rim at a low ridge dubbed ‘Cape York’.
This rock, informally named "Tisdale 2," was the first rock the NASA's Mars Rover Opportunity examined in detail on the rim of Endeavour crater. It has textures and composition unlike any rock the rover examined during its first 90 months on Mars. Its characteristics are consistent with the rock being a breccia -- a type of rock fusing together broken fragments of older rocks. Image credit: NASA/JPL-Caltech/Cornell/ASU
Endeavour’s rim is heavily eroded and discontinuous and divided into a series of segmented and beautiful mountainous ridges that offer a bonanza for science.
“This is not like anything we’ve ever seen before. So this is a new kind of rock.” said Steve Squyres, principal investigator for Opportunity at Cornell University in Ithaca, N.Y at a briefing for reporters on Sept. 1.
“It has a composition similar to some volcanic rocks, but there’s much more zinc and bromine than we’ve typically seen. We are getting confirmation that reaching Endeavour really has given us the equivalent of a second landing site for Opportunity.”
Tisdale 2 is a flat-topped rock about the size of a footstool that was blasted free by the impact that formed the tennis court sized “Odyssey” crater from which it was ejected.
“The other big take-away message, and this is to me the most interesting thing about Tisdale, is that this rock has a huge amount of zinc in it, way more zinc than we have ever seen in any Martian rock. And we are puzzling, we are thinking very hard over what that means,” Squyres speculated.
Bright veins cutting across outcrop in a section of Endeavour crater's rim called "Botany Bay" are visible in the foreground and middle distance of this view assembled from images taken by the navigation camera on Opportunity during Sol 2,681on Mars (Aug. 9, 2011). Credit: NASA/JPL-Caltech
Squyres said that high levels of zinc and bromine on Earth are often associated with rocks in contact with flowing water and thus experiencing hydrothermal activity and that the impact is the source of the water.
“When you find rocks on Earth that are rich in zinc, they typically form in a place where you had some kind of hydrothermal activity going on, in other words, you have water that gets heated up and it flows through the rocks and it can dissolve out and it can get redeposited in various places,” Squyres explained.
“So this is a clue, not definitive proof yet, but this is a clue that we may be dealing with a hydrothermal system here, we may be dealing with a situation where water has percolated or flowed or somehow moved through these rocks, maybe as vapor, maybe as liquid, don’t know yet.”
“But it has enhanced the zinc concentration in this rock to levels far in excess of anything we’ve ever seen on Mars before. So that’s the beginning of what we expect is going to be a long and very interesting story about these rocks.”
Endeavour crater was chosen three years ago as the long term destination for Opportunity because it may hold clues to a time billions and billions of years ago when Mars was warmer and wetter and harbored an environment that was far more conducive to the formation of life beyond Earth.
Endeavour Crater Panorama from Opportunity, Sol 2681, August 2011
Opportunity arrived at the rim of Endeavour on Sol 2681, August 9, 2011 and climbed up the ridge known as Cape York. Odyssey crater is visible at left. The rover has driven to Tisdale 2 rock at the outskirts of Odyssey to investigate the ejecta blocks which may hold clues to ancient water flow on Mars. Distant portions of Endeavour’s rim - as far as 13 miles away – visible in the background. The rover will likely drive eventually to the Cape Tribulation rim segment at right which holds a mother lode of clay minerals. This photo mosaic was stitched together from raw images taken by Opportunity on Sol 2681.
Mosaic Credit: NASA/JPL/Cornell/Marco Di Lorenzo/Kenneth Kremer
Signatures of clay minerals, or phyllosilicates, were detected at several spots at Endeavour’s western rim by observations from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) aboard NASA’s Mars Reconnaissance Orbiter (MRO).
“The motherlode of clay minerals is on Cape Tribulation. The exposure extends all the way to the top, mainly on the inboard side,” said Ray Arvidson, the rover’s deputy principal investigator at Washington University in St. Louis.
Opportunity Traverse Map: 2004 to 2011. The yellow line on this map shows where NASA's Mars Rover Opportunity has driven from the place where it landed in January 2004 -- inside Eagle crater, at the upper left end of the track -- to a point approaching the rim of Endeavour crater. The map traces the route through the 2,670th Martian day, or sol, of Opportunity's work on Mars (July 29, 2011). Image credit: NASA/JPL-Caltech/MSSS/NMMNHS.
Phyllosilicates are clay minerals that form in the presence of pH neutral water and which are far more hospitable to the possible genesis of life compared to the sulfate rich rocks studied in the more highly acidic aqueous environments examined by both the Opportunity and Spirit rovers thus far.
“We can get up the side of Cape Tribulation,” said Arvidson. It’s not unlike Husband Hill for Spirit. We need to finish up first at Cape York, get through the martian winter and then start working our way south along Solander Point.
The general plan is that Opportunity will probably spend the next several months exploring the Cape York region for before going elsewhere. “Just from Tisdale 2 we know that we have something really new and different here,” said Squyres.
“On the final traverses to Cape York, we saw ragged outcrops at Botany Bay unlike anything Opportunity has seen so far, and a bench around the edge of Cape York looks like sedimentary rock that’s been cut and filled with veins of material possibly delivered by water,” said Arvidson. “We made an explicit decision to examine ancient rocks of Cape York first.”
So far at least the terrain at Cape York looks safe for driving with good prospects for mobility.
Opportunity approaches Tisdale 2 rock at Endeavour Crater rim
Opportunity Mars rover climbed up the ridge known as Cape York and drove to the flat topped Tisdale 2 rock at upper left to analyze it with the science instruments on the robotic arm. This photo mosaic was stitched together from raw images taken by Opportunity on Sol 2685, August 2011.
Mosaic Credit: NASA/JPL/Cornell/Marco Di Lorenzo/Kenneth Kremer
“The good news is that, as predicted, we have hard packed soils like the plains at Gusev that Spirit saw before getting to the Columbia Hills,” said Arvidson. “The wheel tracks at Cape York are very, very shallow. So if anything we will have some skid going downhill the slopes of 5 to 10 degrees on the inboard side which we can correct for.”
“We are always on the lookout for sand traps. We are particularly sensitized to that after the Spirit situation. So far it’s clear sailing ahead.”
Opportunity will then likely head southwards towards an area dubbed “Botany Bay” and eventually drive some 1.5 km further to the next ridge named Cape Tribulation and hopefully scale the slopes in an uphill search for that mother lode of phyllosilicates.
“My strong hope – if the rover lasts that long – is that we will have a vehicle that is capable of climbing Cape Tribulation just as we climbed Husband Hill with Spirit. So it’s obvious to try if the rover is capable, otherwise we would try something simpler. But even if we lose a wheel we still have a vehicle capable of a lot of science,” Squyres emphasized. “Then we would stick to lower ground and more gently sloping stuff.”
“The clear intention as we finish up at Cape York, and look at what to do next, is that we are going to work our way south. We will focus along the crater’s rim. We will work south along the rim of Endeavour unless some discovery unexpectedly causes us to do something else.”
“We will go where the science takes us !” Squyres stated.
Opportunity is in generally good health but the rover is showing signs of aging.
“All in all, we have a very senior rover that’s showing her age, she has some arthritis and some other issues but generally, she’s in good health, she’s sleeping well at night, her cholesterol levels are excellent and so we look forward to productive scientific exploration for the period ahead,” said John Callas, project manager for Opportunity at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
“This has the potential to be the most revealing destination ever explored by Opportunity,” said Lavery. “This region is substantially different than anything we’ve seen before. We’re looking at this next phase of Opportunity’s exploration as a whole new mission, entering an area that is significantly different in the geologic context than anything we’ve seen with the rovers.”
This image taken from orbit shows the path of the path driven by NASA's Mars Exploration Rover Opportunity in the weeks around the rover's arrival at the rim of Endeavour crater. The sol number (number of Martian days since the rover landed on Mars) are indicated along the route. Sol 2674 corresponds to Aug. 2, 2011; Sol 2688 corresponds to Aug. 16, 2011. Image credit: NASA/JPL-Caltech/University of ArizonaElevated Zinc and Bromine in Tisdale 2 Rock on Endeavour Rim. This graphic presents information gained by examining part of the Martian rock called "Tisdale 2" with the alpha particle X-ray spectrometer on Mars rover Opportunity and comparing the composition measured there with compositions of other targets examined by Opportunity and its rover twin, Spirit. The comparison targets are soil in Gusev crater, examined by Spirit; the relatively fresh basaltic rock Adirondack, examined by Spirit; the stony meteorite Marquette examined by Opportunity; and Gibraltar, an example of sulfate-rich bedrock examined by Opportunity. The target area on Tisdale 2, called "Timmins 1," contains elevated levels of bromine (Br), zinc (Zn), phosphorus (P), sulfur (S) and chlorine (Cl) relative to the non-sulfate-rich comparison rocks, and high levels of zinc and phosphorus relative to Gibraltar. Credit: NASA/JPL-Caltech/Cornell/Max Planck Institute/University of Guelph
Color image of a region in Holden Crater. Credit: NASA/JPL/University of Arizona
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There could be more subsurface ice on Mars than previously thought, and vast stretches of it may lie just south of the equator. Indeed, one of the proposed landing sites for the Mars Science Laboratory could hold the mother lode of enticing scientific prospects. Observations from two spacecraft, the Mars Reconnaissance Orbiter and Mars Express, have revealed potential subsurface ice deposits in areas just south of the equator, including one near Holden Crater, with an estimated reservoir of perennial subsurface water ice of about 50 – 500 kg m -2 just two or three meters beneath the surface. This is the first evidence of ice at “tropical” latitudes on Mars as low as 25 degrees.
In 2009, MRO observations revealed water ice as low as 45 degrees North in a recent small impact crater, and permanent water ice at Mars’ poles is known to exist. But most robotic missions – and hopefully one day human missions – need to land closer to the equator to meet safety criteria and engineering constraints. As evidence, the four proposed landing sites for the MSL hover within 25 degrees of the equator.*
Of course, subsurface ice can’t be seen directly on Mars, but certain surface characteristics and thermal properties belie potential underground ice. The OMEGA (Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité ) onboard Mars Express and CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) onboard the Mars Reconnaissance Orbiter use near-infrared imaging spectrometers to measure solar radiation scattered by the surface, providing spectral images that have been used to assess the composition of both minerals and condensates on the surface of Mars.
What drew scientists to this region, were observed surface distributions of seasonal CO2 frost on pole facing slopes. Carbon dioxide ice usually only forms on the surface if there is a cold layer beneath, which can come from water ice or bedrock.
But in this case, Mathieu Vincendon and his team at Brown University concluded that bedrock couldn’t be responsible for creating the observed thermal properties that stores and releases heat two or three meters beneath the surface. Evidence of a uniform layer of bedrock stretching across the equatorial region has never been seen in orbital images, which would have been revealed by erosion or impact processes.
“Using different modeling hypotheses within the range of uncertainties leads to the result that water ice is present within one meter of the surface on all 20-30° pole facing slopes down to about 25°S,” the team writes in their paper. “ The relevant thermal depths probed are 2 or 3 meters. Hence, an ice rich layer that thick is implied, which leads to an estimated reservoir of perennial subsurface water ice of about 50 – 500 kg m -2 on steep slopes.”
The team believes that the subsurface ice could be possible remnants of the last ice age on Mars, and could provide water that will be needed for the future exploration of Mars. More thermal measurements of seasonal temperature variations could help to derive more precise permafrost depths.
Holden crater is located at the edge of the subsurface water ice area at 26°S.
*Eberswalde Crater is -23.90 degrees S, Mawrth Vallis is 23.99 degrees N, Gale crater is -4.49 degrees S, and Holden is -26.4 degrees S.
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.
This image shows a river that sprang from a past glacier from an unnamed crater in Mars’ middle latitudes. Credit: NASA/JPL/MSSS
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No sooner do we post one article about water on Mars when it’s time for another. Planetary scientists have uncovered telltale signs of water on Mars — frozen and liquid — in the earliest period of the Red Planet’s history. They found evidence of running water that sprang from glaciers throughout the Martian middle latitudes as recently as the Amazonian epoch, several hundred million years ago. These glaciofluvial valleys were, in essence, tributaries of water created when enough sunlight reached the glaciers to melt a thin layer on the surface. This led to “limited surface melting” that formed channels that ran for several kilometers and could be more than 150 feet wide.
The finding is “more than ‘Yes, we found water,’” said Caleb Fassett from Brown University, who along with Brown research analyst James Dickson, professor James Head III, and geologists from Boston University and Portland State University published a paper in Icarus. “What we see now is there’s this complex history of different environments where water is being formed.”
The team analyzed 15,000 images snapped by the Context Camera (CTX) aboard the Mars Reconnaissance Orbiter to compile the first survey of glaciofluvial valleys on Mars. The survey was sparked by a glaciofluvial valley that Dickson, Fassett, and Head spotted within the Lyot crater, located in the planet’s middle latitudes. The team, in a paper last year in Geophysical Research Letters, dated that meltwater-inspired feature to the Amazonian.
In his survey, Fassett found dozens of other Amazonian-era ice deposits that spawned supraglacial and proglacial valleys, most of them located on the interior and exterior of craters in Mars’ midlatitude belt. “The youthfulness (of the features) is surprising,” he said. “We think of [post-Noachian] Mars as really, really cold and really, really dry, so the fact that these exist, in those kinds of conditions, is changing how we view the history of water on the planet.”
What makes the finding even more intriguing is that the Brown planetary scientists can study what they believe are similar conditions on Earth. Teams from Brown and Boston University have visited the Antarctic Dry Valleys for years, where the surfaces of glaciers melt during the austral summer, sparking enough meltwater to carve a channel. The team will return to the Dry Valleys later this year to continue the study of this microclimate.
“It’s sort of crazy,” said Dickson, a member of the Brown team who stayed in the Dry Valleys for three months last year. “You’re freezing cold and there’s glacial ice everywhere, and it gets just warm enough that you get a river.”
Fassett plans to search for more glaciofluvial valleys as more images come from the CTX, which has mapped roughly 40 percent of the planet.
Locations of nine exposures of hydrated silicate in northern plain craters, shown on a Mars Orbiter Laser Altimeter shaded relief map. Black squares indicate sites investigated with CRISM that did not yield detections. Image courtesy of Science/AAAS.
By looking at the mineralogy deep inside craters on Mars’ northern plains and comparing it to the makeup of regions in the southern hemisphere, scientists have found that widespread liquid water likely altered the majority of Red Planet’s crust about 4 billion years ago. However, the new findings do not support other recent studies that suggest a giant ocean covered Mars’ northern highlands.
Using the Mars Express OMEGA instrument and the Mars Reconnaissance Orbiter’s CRISM instrument, John Carter from Bibring at Université Paris in Orsay, France along with a group of scientists from France and the US, investigated large craters and found minerals which could have only formed in the presence of water. “We’ve detected hydrated minerals in about 10 of these craters,” Carter told Universe Today, “and we conclude that the ancient crust was altered in a similar way both in the south and in the north, in a very early environment which was much warmer and wetter than today’s.”
Carter added that in terms of Mars’ water history, this means liquid water existed near and on the surface of early Mars on a planetary scale, and is not restricted to select areas of the southern highlands.
Mars has dichotomy between north and south, (read our earlier article “The Two Faces of Mars Explained) so while the south is ancient, heavily cratered and high up, the north is smooth, with low-lying plains. It also is much younger and less cratered than the south. This is due to a volcanic mantling processes which filled up part of the lowlands and thus erased any former structures.
HRSC observation of Kunowsky crater, centered at 350.3°E, 56.8°N. (B) CTX close-up (image B01_009932_2370). CRISM mineral maps from observations FRT0000BAD4 and FRT0000C63C are overlaid in red (smectites or chlorite-prehnite) and green (olivine). The white dashed lines indicate the boundaries of the two adjacent observations. (C) HiRISE close-up (image PSP006860_2370) overlain by CRISM mineral maps. No HiRISE data are available over the chlorite-prehnite unit. Image courtesy of Science/AAAS
Carter and his team began their work based on studies of hundreds of sites in the southern hemisphere of Mars which were found to have hydrated minerals which formed on or near the surface some 4 billion ago in a wet and warm environment. While today Mars does not and cannot sustain liquid water on its surface, the scientists knew that a rather weak hydrological system had existed in the southern hemisphere, based on previous geological and morphological evidence.
If minerals in Mars’ northern hemisphere had formed in the presence of water, those minerals would have been buried by the widespread and intense lava flow which happened about 3 billion years ago, resurfacing that region of the planet. But looking into impact craters provides a window into Mars’ past by penetrating down through the lava flow, as well as showering chunks of the underlying crust across the nearby surface.
Carter said the data from OMEGA and CRISM show the mineral assemblages within and around these craters in the north as are very similar to what is seen in the southern ancient highlands, which includes phyllosilicates or other hydrated silicates.
“Our work broadens our view of liquid water on ancient Mars,” Carter said in an email, “spreading it to most of the planet, and may also provide a constraint on the timing of the northern hemisphere alteration with respect to its formation.”
Another conclusion, Carter said, is that these detections may be a constraint on when Mars could have possibly been conducive to the formation of life. “The main scenario which explains the dichotomy is that of an oblique impact between Mars and a fair sized celestial body, thus obliterating and re-melting a great deal of the northern hemisphere of Mars. Such an impact would surely have destroyed any pre-existing hydrated minerals at the depths at which we’re seeing them or we think they come from. Thus the water stability era likely took place after this giant impact, and did not last long (several hundred million years at most). Thus our work may provide a lower limit on this era.”
CTX–HRSC mosaic of Stokes crater, centered at 171.35°E, 55.56°N. (B) CTX closeup (image P20_008686_2356). CRISM mineral maps from observation FRT0000ADA4 are overlain in color. The white dashed lines indicate the boundaries of the CRISM observation. (C) HiRISE close-up (image PSP_009332_2360) of the Al-phyllosilicate “montmorillonite”-bearing unit. The sources of the material are the bright outcrops near the scarp summit (right), whereas the light-toned unit (left) is material transported downslope. (D) HiRISE close-up (image PSP_009332_2360) showing outcrops of olivine, Fe/Mg-, and Al-phyllosilicates in close spatial association. Image courtesy of Science/AAAS
Concerning the giant ocean scenario for the northern highlands, on which a paper was published just last week, Carter said his team’s findings show evidence against those circumstances. “Previous work by a number of teams have actually shown the unlikelihood of a giant northern ocean on Mars younger than 3 billion years as hypothesized by several researchers,” he said. “There is no morphological nor mineralogical evidence for such an ocean. In our 10 or so craters of the northern plains of Mars where we found hydrated minerals, we also found mafic minerals such as olivine. This olivine is almost ubiquitous in northern plain craters, and the vast majority of it is unaltered. Olivine is very readily altered by liquid water hence a giant ocean which would have submerged all these craters should have altered all the olivine, and this is seldom the case.”
Carter said that studying craters from orbit provides a bit of a challenge. “It is hard, for example, to distinguish rocks from orbit which may have been excavated by the impact or actually formed after the impact when the heat released and the existing water and/or ice interacted with the rock to form new minerals, creating hydrothermal environments. In our paper we put forward several reasons why an excavation scenario is favored to a post-impact hydrothermal scenario.”
But craters on Mars provide a better study of the past than craters on Earth, since craters may exist on Mars for billions of year without much degradation, while on Earth water, tectonics and plant growth all conspire to conceal and change craters. Carter said the excavated material on Mars will not be altered by the current ultra-dry, cool environment on the Red Planet.
This research new appears in the June 25, 2010 issue of Science.
Sources: AAAS/Science, email exchange with John Carter
