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This Meteorite Came From a Volcano on Mars

Today, it is well understood that Mars is a cold, dry, and geologically dead planet. However, billions of years ago when it was still young, the planet boasted a denser atmosphere and had liquid water on its surface. Millions of years ago, it also experienced a significant amount of volcanic activity, which resulted in the formation of it’s massive features – like Olympus Mons, the largest volcano in the Solar System.

Until recently, scientists have understood that Martian volcanic activity has been driven by sources other than tectonic movement, which the planet has been devoid of for billions of years. However, after conducting a study of Martian rock samples, a team of researchers from the UK and United States concluded that eons ago, Mars was more volcanically active than previously thought.

Their study, titled “Taking the Pulse of Mars via Dating of a Plume-fed Volcano“, recently appeared in the scientific journal Nature Communications. Led by Benjamin Cohen, a researcher with the Scottish Universities Environmental Research Center (SUERC) and the School of Geographical and Earth Sciences at the University of Glasgow, the team conducted an analysis of Mars’ volcanic past using samples of Martian meteorites.

Asteroid impacts on Mars have sent samples of Martian rock to Earth in the form of meteorites. Credit: geol.umd.edu

On Earth, the majority of volcanism occurs as a result of plate tectonics, which are driven by convection in the Earth’s mantle. But on Mars, the majority of volcanic activity is the result of mantle plumes, which are highly-localized upwellings of magma that rise from deep within the mantle. This is due to the fact that Mars’ surface has remained static and cool for the past few billion years.

Because of this, Martian volcanoes (though similar in morophology to shield volcanoes on Earth), grow to much larger sizes than those on Earth. Olympus Mons, for example, is not only the largest shield volcano on Mars, but the largest in the Solar System. Whereas the tallest mountain on Earth – Mt. Everest – is 8,848 m (29,029 ft) in height, Olympus Mons stands some 22 km (13.6 mi or 72,000 ft) tall.

For the sake of their study, Dr. Cohen and his colleagues used radioscopic dating techniques, which are commonly used to determine the age and eruption rate of volcanoes on Earth. However, such techniques have not been previously used for shield volcanoes on Mars. As a result, the team’s study of Martian meteorite samples was the first detailed analysis of growth rates in Martian volcanoes.

The six samples they examined are known as nakhlites, a class of Martian meteorite that formed from basaltic magma roughly 1.3 billion years ago. These came to Earth roughly 11 million years ago after being were blasted from the face of Mars by an impact event. By conducting an analysis of Martian meteorites, the team was able to uncover about 90 million years’ worth of new information about Mars’ volcanic past.

Color Mosaic of Olympus Mons on Mars
Color mosaic of Mars’ greatest mountain, Olympus Mons, viewed from orbit. Credit NASA/JPL

As Dr. Cohen explained in a University of Glasgow press release:

“We know from previous studies that the nakhlite meteorites are volcanic rocks, and the development of age-dating techniques in recent years made the nakhlites perfect candidates to help us learn more about volcanoes on Mars.”

The first step was to demonstrate that the rock samples were indeed Martian in origin, which the team confirmed by measuring their exposure to cosmogenic radiation. From this, they determined that the rocks were expelled from the Martian surface 11 million years ago, most likely as a result of an impact event on the Martian surface. They then applied a high-precision radioscopic technique known as 40Ar/39Ar dating.

This consisted of using a noble gas mass spectromomer to measure the amount of argon built up in the samples, which is the result of the natural radioactive decay of potassium. From this, they were able to obtain 90 million years’ worth of new information about the Martian surface. The results of their analysis indicated that there are significant differences in volcanic history between the Earth and Mars. As Dr. Cohen explained:

“We found that the nakhlites formed from at least four eruptions over the course of 90 million years. This is a very long time for a volcano, and much longer than the duration of terrestrial volcanoes, which are typically only active for a few million years. And this is only scratching the surface of the volcano, as only a very small amount of rock would have been ejected by the impact crater – so the volcano must have been active for much longer.”

A triple crater in Elysium Planitia on Mars. Credit: NASA/JPL/University of Arizona

In addition, the team was also able to narrow down which volcanoes their rock samples came from. Previous studies conducted by NASA revealed several candidates for the possible nakhlite source crater. However, only one of the locations matched their results in terms of the age of the volcanic eruptions and the impact that would have ejected the samples into space.

This particular crater (which is currently unnamed) is located in the volcanic plains known as Elysium Planitia, roughly 900 km (560 mi) away from summit of the Elysium Mons volcano  – which stands 12.6 km (7.8 mi) tall. It is also located about 2000 km (1243 mi) north of where the NASA Curiosity rover currently is. As Cohen explained, NASA has some wonderfully detailed satellite images of this particular crater.

“It is 6.5 km wide, and has preserved ejecta rays of debris,” he said. “And we were able to see multiple horizontal bands on the crater walls – which indicating the rocks form layers, with each layer interpreted as a separate lava flow. This study has been able to provide a clearer picture into the history of the nakhlite meteorites, and in turn the largest volcanoes in the solar system.”

In the future, sample return and crewed missions to Mars are sure to clear up this picture even further. Given that Mars, like Earth, is a terrestrial planet, knowing all we can about its geological history will ultimately improve our understanding of how the rocky planets of the Solar System formed. In short, the more we know about Mars’ volcanic history, the most we will be able to learn about the Solar System’s formation and evolution.

Further Reading: University of Glasgow, Nature Communications

 

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Study of Martian Sedimentary Layers Reveals More About the Planet’s Past

As of 2016, Mars became the permanent residence of no less than eight robotic missions, a combination of orbiters, rovers and landers. Between extensive studies of the Martian atmosphere and surface, scientists have learned a great deal about the planet’s history and evolution. In particular, they have uncovered voluminous amounts of evidence that Mars once had flowing water on its surface.

The most recent evidence to this effect from the University of Texas at Austin, where researchers have produced a study detailing how water deposited sediment in Mars’ Aeolis Dorsa region. According to their research, this area contains extensive sedimentary deposits that act as a historical record of Mars, cataloguing the influence played by water-based erosion over time.

The study, titled “Fluvial Stratigraphy of Valley Fills at Aeolis Dorsa, Mars: Evidence for Base-Level Fluctuations Controlled by a Downstream Water Body“, recently appeared in the scientific journal GeoScienceWorld. Led by Benjamin D. Cardenas – a geologist with the Jackson School of Geosciences at the University of Texas at Austin – the team examined satellite data of the Aeolis Dorsa region to study the structure of sedimentary deposits.

MOLA Topographic Map of Aeolis Quadrangle (MC-23) on the planet Mars. Credit: USGS

For years, Aeolis Dorsa has been of interest to scientists since it contains some of the most densely-packed sedimentary layers on Mars, which were deposited by flowing water (aka. fluvial deposits). These deposits are visible from orbit because of the way they have undergone a process known as “topographic inversion” – which consists of deposits filling low river channels, then being exhumed to create incised valleys.

By definition, incised valleys are topographic lows produced by “riverine” erosion – i.e. relating to a river or riverbank. On Earth, these valleys are commonly created by rising sea levels, and then filled with sediment as a result of falling sea levels. As sea levels rise, the valleys are cut from the landscape as the waters move inland; and as the sea levels drop, retreating waters deposit sediment within them.

According to the study, this process has created an opportunity for geophysicists and planetary scientist to observe Mars’ geological record in three dimensions and across significant distances. As Cardenas told Universe Today via email:

“Sedimentary rocks in general record information about the environments under which they were deposited. Fluvial (river) deposits specifically record information about the way rivers migrated laterally, the way they aggraded vertically, and how these things changed over time.”
The dotted white arrow points to curved strata recording point bar growth and river migration while the black arrow shows topographically inverted river deposits outcropping as ridges (e.g., black arrow). Credit: hou.usra.edu

Here on Earth, the statigraphy (i.e. the order and position of sedimentary layers) of sedimentary rocks has been used by geologists for generations to place constraints on what conditions were like on our planet billions of years ago. It has only been in recent history that the study of sedimentary layers has been used to place constraints on what environmental conditions were like on other planetary bodies (like Mars) billions of years ago.

However, most of these studies have produced data that has been unable to resolve sedimentary packaging at the sub-meter scale. Instead, satellite images have been used to define large-scale stratigraphic relationships, such as deposition patterns along past water channels. In other words, the studies have focused on cataloging the existence of past water flows on Mars more than what has happened since then.

As Cardenas indicated, he and his team took a different approach, one which considered that Mars has experienced changes over the past 3.5 billion years. As he explained:

“In general, there has been the assumption that a lot of the martian surface is not particularly different than it was 3.5 billion years ago. We make an effort to demonstrate that the modern surface at our study area, Aeolis Dorsa, is the result of burial, exhumation, and un-equal erosion, and it can’t be assumed that the modern surface represents the ancient surface at all. We really try to show that what we see today, the features we can measure today, are sedimentary deposits of rivers, and not actual rivers. This is incredibly important to realize when you start making interpretations of your observations, and it is frequently a missed point.”
Perspective view of Reull Vallis based on images taken by the ESA’s Mars Express. Reull Vallis, a river-like structure, is believed to have formed when running water flowed in the distant martian past. Credit and Copyright: ESA/DLR/FU Berlin (G. Neukum)

For the sake of their research, Cardenas and his team used stereo pairs of high-resolution images and topographic data taken by the Context Camera (CTX) and the High Resolution Imaging Science Experiment (HiRISE) aboard the Mars Reconnaissance Orbiter (MRO). This data was then combined with the Integrated Software for Imagers and Spectrometers (ISIS) –  a digital image-processing package used by the U.S. Geological Survey (USGS) – and NASA’s Ames Stereo Pipeline.

These processed the paired images into high-resolution topographic data and digital elevation models (DEMs) which were then compared to data from the Mars Orbiting Laser Altimeter (MOLA) instrument aboard the Mars Global Surveyor (MSG). The final result was a series of DEMs that were orders of magnitude higher in terms of resolution than anything previously produced.

For all of this, Cardenas and his colleagues were able to identify stacking patterns in the fluvial deposits, noted changes in sedimentation styles, and suggested mechanisms for their creation. In addition, the team introduced a brand new method to measure the flow direction of the rivers that left these deposits, which allowed them to see how the landscape has changed over the past few billion years.

“The study shows there was a large body of water on Mars ~3.5 billion years ago, and that this body of water increased and decreased in volume slowly enough that river sedimentation had time to adjust styles,” said Cardenas. “This is more in line with slower climatic changes, and less in line with catastrophic hydrologic events. Aeolis Dorsa is positioned along hypothesized coastlines of an ancient northern ocean on Mars. It’s interesting to find coastal river deposits at Aeolis Dorsa, but it doesn’t help us constrain the size of the water body (lake, ocean, etc.)”

Nanedi Valles, a roughly 800-kilometre valley believed to be caused by ground-water outflow. Copyright ESA/DLR/FU Berlin (G. Neukum)

In essence, Cardenas and his colleagues concluded that – similar to Earth – falling and rising water levels in a large water body forced the formation of the paleo-valleys in their study area. And in a way that is similar to what is happening on Earth today, rivers that formed in coastal regions were strongly influenced by changes in water levels of a large, downstream water body.

For some time, it has been something of a foregone conclusion that the surface of Mars is dead, its features frozen in time. But as this study demonstrated, the landscape has undergone significant changes since it lost its atmosphere and surface water. These findings will no doubt be the subject of interest as we get closer to mounting a crewed mission to the Martian surface.

Further Reading: GSA, GeoScienceWorld

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Dinosaur Killing Asteroid Hit in Exactly the Wrong Place

When an asteroid struck the Yucatan region about 66 million years ago, it triggered the extinction of the dinosaurs. ESA's Hera mission is visiting the smallest spacerock ever as part of our effort to not get creamed by an asteroid. Credit: NASA/Don Davis

The asteroid that struck Earth about 66 million years ago and led to the mass extinction of dinosaurs may have hit one of the worst places possible as far as life on Earth was concerned. When it struck, the resulting cataclysm choked the atmosphere with sulphur, which blocked out the Sun. Without the Sun, the food chain collapsed, and it was bye-bye dinosaurs, and bye-bye most of the other life on Earth, too.

But, as it turns out, if it had struck a few moments earlier or later, it would not have hit the Yucatan, and things may have turned out differently. Why? Because of the concentration of the mineral gypsum in that area.

The place where the asteroid hit Earth is called the Chicxulub Crater, and scientists have been studying that area to try to learn more about the impact event that altered the course of life on Earth. An upcoming BBC documentary called “The Day The Dinosaurs Died,” focuses on what happened when the asteroid struck. Drill-core samples from the Yucatan area help explain the events that followed the impact.

The drilling rig off the coast of the Yucatan. The rig was there in the Spring of 2016 obtaining samples from the seafloor. Image: BBC/Barcroft Productions.
The drilling rig off the coast of the Yucatan. The rig was there in the Spring of 2016 obtaining samples from the seafloor. Image: BBC/Barcroft Productions.

The core samples, which are from as deep as 1300 m beneath the Gulf of Mexico, are from a feature called the peak ring.

When the asteroid struck Earth, it excavated a crater 100 km across and 30 km deep. This crater collapsed into a wider but shallower crater 200 km across and a few km deep. Then the center of the crater rebounded, and collapsed again, leaving the peak ring feature. The Chicxulub crater is now partly under water, and that’s where a drilling rig was set up to take samples.

The peak ring is at the center of the crater, offshore of the Yucatan Peninsula. Image: NASA/BBC
The peak ring is at the center of the crater, offshore of the Yucatan Peninsula. Image: NASA/BBC

The core samples revealed rock that has been heavily fractured and altered by immense pressures. The same impact that altered those rocks would have generated an enormous amount of heat, and that heat created an enormous cloud of sulphur from the vaporized gypsum. That cloud persisted, which led to a global winter. Temperatures dropped, plant growth came to a standstill, and the course of events on Earth were altered forever.

“Had the asteroid struck a few moments earlier or later, rather than hitting shallow coastal waters it might have hit deep ocean,” documentary co-presenter Ben Garrod told the BBC.

“This is where we get to the great irony of the story – because in the end it wasn’t the size of the asteroid, the scale of blast, or even its global reach that made dinosaurs extinct – it was where the impact happened,” said Ben Garrod, who presents “The Day The Dinosaurs Died” with Alice Roberts.

“An impact in the nearby Atlantic or Pacific oceans would have meant much less vaporised rock – including the deadly gypsum. The cloud would have been less dense and sunlight could still have reached the planet’s surface, meaning what happened next might have been avoided,” said Garrod.

In the documentary, host Alice Roberts will also visit a quarry in New Jersey, where fossil evidence shows a massive die-off in a very short period of time. In fact, these creatures could have died on the very day that the asteroid struck.

The core samples from the drilling rig show rocks that were subjected to immense heat and pressure at the time of the impact. Image: Barcroft Productions/BBC
The core samples from the drilling rig show rocks that were subjected to immense heat and pressure at the time of the impact. Image: Barcroft Productions/BBC

“All these fossils occur in a layer no more than 10cm thick,” palaeontologist Ken Lacovara tells Alice. “They died suddenly and were buried quickly. It tells us this is a moment in geological time. That’s days, weeks, maybe months. But this is not thousands of years; it’s not hundreds of thousands of years. This is essentially an instantaneous event.”

There’s lots of evidence showing that an asteroid struck Earth about 66 million years ago, causing widespread extinction. NASA satellite images clearly show crater features, now obscured by 66 million years of geological activity, but still visible.

There’s also what’s called the K-T Boundary, or Cretaceous-Tertiary Boundary. It’s a geological signature dating to 66 million years ago, which marks the end of the Cretaceous Period. In that boundary is a layer of iridium at very high concentrations, much higher than is normally present in the Earth’s crust. Since iridium is much more abundant in asteroids, the conclusion is that it was probably deposited by an asteroid.

But this is the first evidence that shows how critical the actual location of the event may have been. If it had not struck where it had, dinosaurs may never have gone extinct, you and I would not be here, and things on Earth could look much different.

It might sound like the stuff of science fiction, but who knows? Maybe a race of intelligent lizards might already have mastered interstellar travel.

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Ceres Prank Lands Bart Simpson In Detention For Eternity

Do you see Bart Simpson's face on these surface features on Ceres? Researchers studying the surface of the dwarf planet for evidence of the presence of ice do. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera

Human-kind has a long history of looking up at the stars and seeing figures and faces. In fact, there’s a word for recognizing faces in natural objects: pareidolia. But this must be the first time someone has recognized Bart Simpson’s face on an object in space.

Researchers studying landslides on the dwarf planet Ceres noticed a pattern that resembles the cartoon character. The researchers, from the Georgia Institute of Technology, are studying massive landslides that occur on the surface of the icy dwarf. Their findings are reinforcing the idea that Ceres has significant quantities of frozen water.

Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera
Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera

In a new paper in the journal Nature Geoscience, the team of scientists, led by Georgia Tech Assistant Professor and Dawn Science Team Associate Britney Schmidt, examined the surface of Ceres looking for morphologies that resemble landslides here on Earth.

Research shows us that Ceres probably has a subsurface shell that is rich with water-ice. That shell is covered by a layer of silicates. Close examination of the type, and distribution, of landslides at different latitudes adds more evidence to the sub-surface ice theory.

Ceres is pretty big. At 945 km in diameter, it’s the largest object in the asteroid belt between Mars and Jupiter. It’s big enough to be rounded by its own gravity, and it actually comprises about one third of the mass of the entire asteroid belt.

Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera
Type 1 landslides on Ceres are large and occur at higher latitudes. Image: Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera

The team used observations from the Dawn Framing Camera to identify three types of landslides on Ceres’ surface:

  • Type 1 are large, rounded features similar to glacier features in the Earth’s Arctic region. These are found mostly at high latitudes on Ceres, which is where most of the ice probably is.
  • Type 2 are the most common. They are thinner and longer than Type 1, and look like terrestrial avalanche deposits. They’re found mostly at mid-latitudes on Ceres. The researchers behind the study thought one of them looked like Bart Simpson’s face.
  • Type 3 occur mostly at low latitudes near Ceres’ equator. These are always found coming from large impact craters, and probably formed when impacts melted the sub-surface ice.
Type 3 landslides on Ceres occur at low latitudes at large craters, and form when ice is melted by impacts. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera
Type 3 landslides on Ceres occur at low latitudes at large craters, and form when ice is melted by impacts. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA, taken by Dawn Framing Camera

The authors of the study say that finding larger landslides further away from the equator is significant, because that’s where most of the ice is.

“Landslides cover more area in the poles than at the equator, but most surface processes generally don’t care about latitude,” said Schmidt, a faculty member in the School of Earth and Atmospheric Sciences. “That’s one reason why we think it’s ice affecting the flow processes. There’s no other good way to explain why the poles have huge, thick landslides; mid-latitudes have a mixture of sheeted and thick landslides; and low latitudes have just a few.”  

Key to understanding these results is the fact that these types of processes have only been observed before on Earth and Mars. Earth, obviously, has water and ice in great abundance, and Mars has large quantities of sub-surface ice as well. “It’s just kind of fun that we see features on this small planet that remind us of those on the big planets, like Earth and Mars,” Schmidt said. “It seems more and more that Ceres is our innermost icy world.”

“These landslides offer us the opportunity to understand what’s happening in the upper few kilometers of Ceres,” said Georgia Tech Ph.D. student Heather Chilton, a co-author on the paper. “That’s a sweet spot between information about the upper meter or so provided by the GRaND (Gamma Ray and Neutron Detector) and VIR (Visible and Infrared Spectrometer) instrument data, and the tens of kilometers-deep structure elucidated by crater studies.”

It’s not just the presence of these landslides, but the frequency of them, that upholds the icy-mantle idea on Ceres. The study showed that 20% to 30% of craters on Ceres larger than 10 km have some type of landslide. The researchers say that upper layers of Ceres’ could be up to 50% ice by volume.

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Earth Just Got A New Continent

We tend to lump New Zealand and Australia together. They’re similar culturally and share the same geographical position, relative to North America and Europe, anyway. But according to a new paper published in the Geological Society of America Today, it looks like New Zealand and their neighbor New Caledonia are actually their own continent: ‘Zealandia.’

Continent means something different to geographers and geologists. To be considered a geological continent, like Zealandia, the area in question has to satisfy a few conditions:

  • the land in question has to be higher than the ocean floor
  • it has to include a broad range of siliceous igneous, metamorphic, and sedimentary rocks
  • it has to have thicker crust than the ocean floor that surrounds it
  • it has to have well-defined limits, and be large enough to be considered a continent

In Geology, the first three points are well-understood. But as the authors say in the introduction to their paper, “…the last point—how “major” a piece of continental crust has to be to be called a continent—is almost never discussed… .” Since the Earth has so many micro-continents and continental fragments, defining how large something has to be to be called a continent is challenging. But the researchers did their homework.

They noted that the term “Zealandia” has been used before to describe New Zealand and surrounding regions. But the boundaries were never fully explored. 94% of this new continent is submerged, which helps explain why it’s taken this long to be identified.

This map shows the spatial limits of Zealandia. Note the dotted red line that delineates continental crust from ocean crust. Zealandia is also bisected by a plate boundary between the Pacific Plate and the Australian Plate. Image: Mortimer et. al. 2017, GSA Today

Zealandia seemed to be a collection of broken pieces, but new data collected over the years has challenged that interpretation. Recent satellite data has given us new gravity and elevation maps of the seafloor. This data has shown that Zealandia is a unified region large as large as India.

“This is not a sudden discovery but a gradual realization; as recently as 10 years ago we would not have had the accumulated data or confidence in interpretation to write this paper.”

As the authors point out in their paper, it took a while to determine that Zealandia is a continent. There was no Eureka moment. “This is not a sudden discovery but a gradual realization; as recently as 10 years ago we would not have had the accumulated data or confidence in interpretation to write this paper.”

Besides satisfying our intellectual curiosity about our planet, the discovery is important for other reasons. A proper understanding of the plate structures and continental boundaries is important to other sciences, and may trigger further understandings that we can’t predict yet. It may also point to other areas of research.

Also, many treaties rely on the agreed upon delineation of maritime and continental boundaries, including rights to fish stocks and underground resources. While the recognition of Zealandia seems clear from a scientific standpoint, it remains to be seen if it will be accepted politically.

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Curiosity’s Martian Chronicles Rife With Intriguing Inconsistencies

The study of Mars’ surface and atmosphere has unlocked some ancient secrets. Thanks to the efforts of the Curiosity rover and other missions, scientists are now aware of the fact that water once flowed on Mars and that the planet had a denser atmosphere. They have also been able to deduce what mechanics led to this atmosphere being depleted, which turned it into the cold, desiccated environment we see there today.

At the same time though, it has led to a rather intriguing paradox. Essentially, Mars is believed to have had warm, flowing water on its surface at a time when the Sun was one-third as warm as it is today. This would require that the Martian atmosphere had ample carbon dioxide in order to keep its surface warm enough. But based on the Curiosity rover’s latest findings, this doesn’t appear to be the case.

These findings were part of an analysis of data taken by the Curiosity’s Chemistry and Mineralogy X-ray Diffraction (CheMin) instrument, which has been used to study the mineral content of drill samples in the Gale Crater. The results of this analysis were recently published in Proceedings of the National Academy of Science, where the research team indicated that no traces of carbonates were found in any samples taken from the ancient lake bed.

Simulated view of Gale Crater Lake on Mars, depicting a lake of water partially filling Mars’ Gale Crater. Credit: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

To break it down, evidence collected by Curiosity (and a slew of other rovers, landers and orbiters) has led scientists to conclude that roughly 3.5 billion years ago, Mars surface had lakes and flowing rivers. They have also determined, thanks to the many samples taken by Curiosity since it landed in the Gale Crater in 2011, that this geological feature was once a lake bed that gradually became filled with sedimentary deposits.

However, for Mars to have been warm enough for liquid water to exist, its atmosphere would have had to contain a certain amount of carbon dioxide – providing a sufficient Greenhouse Effect to compensate for the Sun’s diminished warmth. Since rock samples in the Gale Crater act as a geological record for what conditions were like billions of years ago, they would surely contain plenty of carbonate minerals if this were the case.

Carbonates are minerals that result from carbon dioxide combining with positively charged ions (like magnesium and iron) in water. Since these ions have been found to be in good supply in samples of Martian rock, and subsequent analysis has shown that conditions never became acidic to the point that the carbonates would have dissolved, there is no apparent reason why they wouldn’t be showing up.

Along with his team, Thomas Bristow – the principal investigator for the CheMin instrument on Curiosity – calculated what the minimum amount of atmospheric carbon dioxide would need to be, and how this would have been indicated by the levels of carbonate found in Martian rocks today. They then sorted through the years worth of the CheMin instrument’s data to see if there were any indications of these minerals.

Comparison of X-ray diffraction patterns of two different samples analyzed by Curiosity’s Chemistry and Mineralogy (CheMin) instrument. Credit: NASA/JPL-Caltech/Ames

But as he explained in a recent NASA press release, the findings simply didn’t measure up:

“We’ve been particularly struck with the absence of carbonate minerals in sedimentary rock the rover has examined. It would be really hard to get liquid water even if there were a hundred times more carbon dioxide in the atmosphere than what the mineral evidence in the rock tells us.”

In the end, Bristow and his team could not find even trace amounts of carbonates in the rock samples they analyzed. Even if just a few tens of millibars of carbon dioxide had been present in the atmosphere when a lake existed in the Gale Crater, it would have produced enough carbonates for Curiosity’s CheMin to detect. This latest find adds to a paradox that has been plaguing Mars researchers for years.

Basically, researchers have noted that there is a serious discrepancy between what surface features indicate about Mars’ past, and what chemical and geological evidence has to say. Not only is there plenty of evidence that the planet had a denser atmosphere in the past, more than four decades of orbital imaging (and years worth of surface data) have yielded ample geomorphological evidence that Mars once had surface water and an active hydrological cycle.

The Gale Crater – the landing location and trek of the Rover Curiosity – as it is today, imaged by the MRO. Credits: NASA/JPL, illustration, T.Reyes

However, scientists are still struggling to produce models that show how the Martian climate could have maintained the types of conditions necessary for this to have been the case. The only successful model so far has been one in which the atmosphere contained a significant amount of CO2 and hydrogen. Unfortunately, an explanation for how this atmosphere could be created and sustained remains elusive.

In addition, the geological and chemical evidence for such a atmosphere existing billions of years ago has also been in short supply. In the past, surveys by orbiters were unable to find evidence of carbonate minerals on the surface of Mars. It was hoped that surface missions, like Curiosity, would be able to resolve this by taking soil and drill samples where water had been known to exist.

But as Bristow explained, his team’s study has effectively closed the door on this:

“It’s been a mystery why there hasn’t been much carbonate seen from orbit. You could get out of the quandary by saying the carbonates may still be there, but we just can’t see them from orbit because they’re covered by dust, or buried, or we’re not looking in the right place. The Curiosity results bring the paradox to a focus. This is the first time we’ve checked for carbonates on the ground in a rock we know formed from sediments deposited under water.”

Annontated version of the bedrock site in the Gale Crater where the Curiosity rover has taken drill samples. Credit: NASA/JPL-Caltech/MSSS

There are several possible explanations for this paradox. On the one hand, some scientists have argued that the Gale Crater Lake may not have been an open body of water and was perhaps covered in ice, which was just thin enough to still allow for sediments to get in. The problem with this explanation is that if this were true, there would be discernible indications left behind – which would include deep cracks in the soft sedimentary lakebed rock.

But since these indications have not been found, scientists are left with two lines of evidence that do not match up. As Ashwin Vasavada, Curiosity’s Project Scientist, put it:

“Curiosity’s traverse through streambeds, deltas, and hundreds of vertical feet of mud deposited in ancient lakes calls out for a vigorous hydrological system supplying the water and sediment to create the rocks we’re finding. Carbon dioxide, mixed with other gases like hydrogen, has been the leading candidate for the warming influence needed for such a system. This surprising result would seem to take it out of the running.”

Luckily, incongruities in science are what allow for new and better theories to be developed. And as the exploration of the Martian surface continues  – which will benefit from the arrival of the ExoMars and the Mars 2020 missions in the coming years – we can expect additional evidence to emerge. Hopefully, it will help point the way towards a resolution for this paradox, and not complicate our theories even more!

Further Reading: NASA

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Meteorite Confirms 2 Billion Years of Volcanic Activity on Mars

Color Mosaic of Olympus Mons on Mars

Mars is renowned for having the largest volcano in our Solar System, Olympus Mons. New research shows that Mars also has the most long-lived volcanoes. The study of a Martian meteorite confirms that volcanoes on Mars were active for 2 billion years or longer.

A lot of what we know about the volcanoes on Mars we’ve learned from Martian meteorites that have made it to Earth. The meteorite in this study was found in Algeria in 2012. Dubbed Northwest Africa 7635 (NWA 7635), this meteorite was actually seen travelling through Earth’s atmosphere in July 2011.

A sample from the meteorite Northwest Africa 7635. Image: Mohammed Hmani
A sample from the meteorite Northwest Africa 7635. Image: Mohammed Hmani

The lead author of this study is Tom Lapen, a Geology Professor at the University of Houston. He says that his findings provide new insights into the evolution of the Red Planet and the history of volcanic activity there. NWA 7635 was compared with 11 other Martian meteorites, of a type called shergottites. Analysis of their chemical composition reveals the length of time they spent in space, how long they’ve been on Earth, their age, and their volcanic source. All 12 of them are from the same volcanic source.

Mars has much weaker gravity than Earth, so when something large enough slams into the Martian surface, pieces of rock are ejected into space. Some of these rocks eventually cross Earth’s path and are captured by gravity. Most burn up, but some make it to the surface of our planet. In the case of NWA 7635 and the other meteorites, they were ejected from Mars about 1 million years ago.

“We see that they came from a similar volcanic source,” Lapen said. “Given that they also have the same ejection time, we can conclude that these come from the same location on Mars.”

Taken together, the meteorites give us a snapshot of one location of the Martian surface. The other meteorites range from 327 million to 600 million years old. But NWA 7635 was formed 2.4 billion years ago. This means that its source was one of the longest lived volcanoes in our entire Solar System.

This false color X-ray of NWA 7635 shows the meteorite’s mineralogy mineral textures. O, olivine; P, plagioclase (maskelynite); C, clinopyroxene (augite). Chemical compositions: Fe (purple), Mg (green), Ca (blue), Ti (magenta), and S (yellow). Purple colors in the mesostasis represent Fe-rich augite. You’re welcome, mineral nerds. Image: Lapen et. al.

Volcanic activity on Mars is an important part of understanding the planet, and whether it ever harbored life. It’s possible that so-called super-volcanoes contributed to extinctions here on Earth. The same thing may have happened on Mars. Given the massive size of Olympus Mons, it could very well have been the Martian equivalent of a super-volcano.

The ESA’s Mars Express Orbiter sent back images of Olympus Mons that showed possible lava flows as recently as 2 million years ago. There are also lava flows on Mars that have a very small number of impact craters on them, indicating that they were formed recently. If that is the case, then it’s possible that Martian volcanoes will be visibly active again.

A colorized image of the surface of Mars taken by the Mars Reconnaissance Orbiter. The line of three volcanoes is the Tharsis Montes, with Olympus Mons to the northwest. Valles Marineris is to the east. Image: NASA/JPL-Caltech/ Arizona State University
A colorized image of the surface of Mars taken by the Mars Reconnaissance Orbiter. The line of three volcanoes is the Tharsis Montes, with Olympus Mons to the northwest. Valles Marineris is to the east. Image: NASA/JPL-Caltech/ Arizona State University

Continuing volcanic activity on Mars is highly speculative, with different researchers arguing for and against it. The relatively crater-free, smooth surfaces of some lava features on Mars could be explained by erosion, or even glaciation. In any case, if there is another eruption on Mars, we would have to be extremely lucky for one of our orbiters to see it.

But you never know.

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JPL Needs Citizen Scientists To Hunt Martian Polygonal Ridges

Mars has some impressive geological features across its cold, desiccated surface, many of which are similar to featured found here on Earth. By studying them, scientists are able to learn more about the natural history of the Red Planet, what kinds of meteorological phenomena are responsible for shaping it, and how similar our two planets are. A perfect of example of this are the polygon-ridge networks that have been observed on its surface.

One such network was recently discovered by the Mars Reconnaissance Orbiter (MRO) in the Medusae Fossae region, which straddles the planet’s equator. Measuring some 16 story’s high, this ridge network is similar to others that have been spotted on Mars. But according to a survey produced by researchers from NASA’s Jet Propulsion Laboratory, these ridges likely have different origins.

This survey, which was recently published in the journal Icarus, examined both the network found in the Medusae Fossae region and similar-looking networks in other regions of the Red Planet. These ridges (sometimes called boxwork rides), are essentially blade-like walls that look like multiple adjoining polygons (i.e. rectangles, pentagons, triangles, and similar shapes).

 Shiprock, a ridge-feature in northwestern New Mexico that is 10 meters (30 feet) tall, which formed from lava filling an underground fracture that resisted erosion better than the material around it did. Credit: NASA

While similar-looking ridges can be found in many places on Mars, they do not appear to be formed by any single process. As Laura Kerber, of NASA’s Jet Propulsion Laboratory and the lead author of the survey report, explained in a NASA press release:

“Finding these ridges in the Medusae Fossae region set me on a quest to find all the types of polygonal ridges on Mars… Polygonal ridges can be formed in several different ways, and some of them are really key to understanding the history of early Mars. Many of these ridges are mineral veins, and mineral veins tell us that water was circulating underground.”

Such ridges have also been found on Earth, and appear to be the result of various processes as well. One of the most common involves lava flowing into preexisting fractures in the ground, which then survived when erosion stripped the surrounding material away. A good example of this is the Shiprock (shown above), a monadrock located in San Juan County, New Mexico.

Examples of polygon ridges on Mars include the feature known as “Garden City“, which was discovered by the Curiosity rover mission. Measuring just a few centimeters in height, these ridges appeared to be the result of mineral-laden groundwater moving through underground fissures, which led to standing mineral veins once the surrounding soil eroded away.

Mineral veins at the “Garden City” site, examined by NASA’s Curiosity Mars rover. Credit: NASA/JPL

At the other end of the scale, ridges that measure around 2 kilometers (over a mile) high have also been found. A good example of this is “Inca City“, a feature observed by the Mars Global Surveyor near Mars’ south pole. In this case, the feature is believed to be the result of underground faults (which were formed from impacts) filling with lava over time. Here too, erosion gradually stripped away the surrounding rock, exposing the standing lava rock.

In short, these features are evidence of underground water and volcanic activity on Mars. And by finding more examples of these polygon-ridges, scientists will be able to study the geological record of Mars more closely. Hence why Kerber is seeking help from the public through a citizen-science project called Planet Four: Ridges.

Established earlier this month on Zooniverse – a volunteer-powered research platform – this project has made images obtained by the MRO’s Context Camera (CTX) available to the public. Currently, this and other projects using data from CTX and HiRISE have drawn the participation of more than 150,000 volunteers from around the world.

By getting volunteers to sort through the CTX images for ridge formations, Kerber and her team hopes that previously-unidentified ones will be identified and that their relationship with other Martian features will be better understood.

Further Reading: NASA

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What is the World’s Deepest Ocean?

One look at planet Earth on a map, or based on an image taken from space, ought to convey just how immense and important our oceans are. After all, they cover 72% of the planet’s surface, occupy a total volume of around 1.35 billion cubic kilometers (320 million cu mi), and are essential to life as we know it. And in their great depths, many mysteries still wait to be discovered.

Thanks to modern science and improvement exploration vehicles, one of the most obvious has been tackled – which is the mystery of where the deepest ocean in the world lies. This is none other than the Pacific Ocean, which  averages approximately 4,280 meters (14,042 ft) in depth and contains the deepest known part of any ocean – the Mariana Trench.

Methodology:

Of course, determining the depth of an ocean is tricky business, and for obvious reasons. Ocean floors are extremely extensive, and vary widely in terms of elevation. Much like continental land masses, they have mountain ranges and trenches that throw off the curve. And in some cases, the trenches are much deeper than the average depth.

Oceans
The view of the Pacific Ocean from the ISS. Credit: NASA

However, in terms of average depth, the Pacific Ocean is the deepest. Though calculations vary, it is estimated that the entire ocean floor averages about 4,280 meters (14,042 ft), which is over 500 m (1640 ft) deeper than the global average of 3,700 meters (12,100 ft). Part of the reason for this is due to the Marian Trench, which is significantly deeper!

Characteristics:

The Marian Trench is located in the western Pacific Ocean near the Mariana Islands, almost equally distant from both the Philippines and Japan. The trench is crescent shaped, and measures roughly 2,550 kilometers (1,580 mi) long with an average width of 69 kilometers (43 mi).

It reaches a maximum-known depth of 10,994 meters (36,070 ft) – with a margin of error of 40 metes (130 ft) – at a small slot-shaped valley in its floor known as the Challenger Deep, located at its southern end. Countries near the trench include Japan, Papua New Guinea, Indonesia and the Philippines.

The geological feature is the result of subduction that occurs at the boundary between two tectonic plates – the Filipino and the Pacific Plate. This results in what is known as the Izu-Bonin-Mariana subduction system, where the western edge of the Pacific Plate is subducted (pushed under) the smaller Mariana plate (part of the Filipino Plate).

Location of the Mariana Trench. Credit: Wikipedia Commons/Kmusser
Location of the Mariana Trench. Credit: Wikipedia Commons/Kmusser

The movement of the Pacific and Mariana Plates also led to the formation of the Mariana Islands, which are volcanic in nature. They formed as a result of flux melting – i.e. where water cools hot lava – due to the release of water that was trapped in the subducted portion of the Pacific Plate.

To put just how deep the Mariana Trench is into perspective, let’s consider comparing it to Mount Everest. If you placed Mt. Everest inside the Mariana Trench, there would still be over 2,000 meters (6562 ft) of water covering the mountain.

The water pressure in the Mariana Trench is also 15,750 psi, which is more than 1000 times greater than the standard atmospheric pressure at sea level. This means that if you could stand at the bottom of the Mariana Trench, the pressure could literally crush you!

Measurement:

Numerous measurements of the trench have been taken over the years using different methods. The first mission was the Challenger expedition, which took place between 1872 and 1876. Using the sounding technique, they measured the deepest point of Mariana Trench to 9,636 meters (31,614 ft).

The HMS Challenger, which made the first measurements of the Mariana Trench. Credit: Imperial War Museums.
The HMS Challenger, which conducted the Challenger II measurements of the Mariana Trench. Credit: Imperial War Museums.

This was followed by the HMS Challenger, which conducted the Challenger II survey in 1931. Here, surveyors relied on the more accurate technique of echo-sounding, and retrieved a deepest measurement of 10,900 meters (35,760 ft). This area came to be known as the Challenger Deep.

During the latter half of the 20th century, multiple missions would be conducted. In 1957, the Soviet vessel Vityaz obtained depth readings of 11,034 meters (36,201 ft) at a location named “the Mariana Hollow”. This was followed in 1962 by the US merchant vessel Spencer F. Baird, which recorded a maximum depth of 10,915 meters (35,810 ft) using precision depth gauges.

In 1984, the Japanese survey vessel Takuyo used a narrow, multi-beam echo sounder and reported a maximum depth of 10,924 meters (35,840 ft). In 1995, another Japanese vessel – the remotely operated vehicle KAIKO – reached the deepest area of the Mariana trench, thus establishing the deepest diving record of 10,911 meters (35,797 ft).

In 2009, the US research vessel Kilo Moana conducted the most accurate measurements of the Mariana Trench to date. This involved using sonar to map the Challenger Deep, which located a spot with a maximum depth of 10,971 meters (35,994 ft).

Rear view of the research vessel Kilo Moana. NOAA
Rear view of the research vessel Kilo Moana. NOAA

Exploration:

Four missions have been made into the Mariana Trench. The first was the Trieste, a Swiss-designed, Italian-built, and US Navy-owned self-propelled submersible craft. On January 23rd, 1960, the craft and its two-man crew reached the bottom of the Trench, having reached a depth of 10,916 m (35,814 ft). This was followed by the unmanned Kaiko craft in 1996 and the autonomous craft Nereus in 2009.

The first three expeditions directly measured very similar depths of 10,902 to 10,916 m (35,768 to 35,814 ft). The fourth mission took place in 2012, where Canadian film director James Cameron mounted a mission using the submersible Deepsea Challenger. On March 26th, he reached the bottom of the Mariana Trench.

Several more missions have been planned as of February of 2012. These include Triton Submarines, a Florida-based company that designs and manufactures private submarines; and DOER Marine, a marine technology company based near San Francisco that plans to send a two or three-person sub to the seabed.

Beyond the coastlines, the world’s oceans are deep and unfathomable. Much of it remains unexplored and the life that scientists have found there is quite exotic (and may even provide insight into life on other worlds). Somehow, it seems appropriate that life in “inner space” would help us to understand life in “outer space”.

We have written many interesting articles about the Pacific Ocean here at Universe Today. Here’s How Many Oceans are there in the World?, What Causes Tides?, Did Comets Create the Earth’s Oceans?, and What Percentage of Earth is Water?

If you are looking for more information, you should try this article from National Geographic on life in the Mariana Trench  and this website on the Mariana Trench.

Astronomy Cast has an episode on the subject – Episode 51: Earth.

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