Tag: geology

Increased earthquake activity at Mount St. Helens

12:37 pm

Though the increase is not large enough to indicate the likelihood of another eruption, scientists have noted that for the past eight weeks the earthquake rates under Mount St. Helens has been increasing.

Over the last 8 weeks, there have been over 130 earthquakes formally located by the Pacific Northwest Seismic Network and many more earthquakes too small to be located. The earthquakes have low magnitudes of 0.5 or less; the largest a magnitude 1.3. Earthquake rates have been steadily increasing since March, reaching nearly 40 located earthquakes per week. These earthquakes are too small to be felt at the surface.

Once again, these quakes do yet not signal another eruption. They are more likely signs of the mountain’s continuing but long and slow adjustment back to silence after the 1980 eruption. Nonetheless, they bear watching, as a volcano will do what a volcano wants to do.

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Ice and volcanoes on ancient Mars?

1:03 pm

New data of past volcanic activity on Mars suggest that the red planet was once covered by at least one extensive ice sheet.

There is a great deal of uncertainty in this conclusion, however. They have found one example with the right geology to suggest past ice sheets under which volcanoes erupted. Translating this into an extensive ice sheet requires many assumptions that might not prove true with further research.

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Halo craters on Pluto

4:48 pm

More images from New Horizons reveal even more strange terrain on Pluto.

Data suggest that the bright rims are made of methane ice, while the dark crater floors are made of water ice, though why this has happened is a complete mystery. As they note at the link above, “Exactly why the bright methane ice settles on these crater rims and walls is a mystery; also puzzling is why this same effect doesn’t occur broadly across Pluto.”

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Evidence of water on Ceres?

9:21 am

water on Ceres?

New data from Dawn suggests that there is significant water locked in surface of Ceres’s north polar regions.

These data reflect the concentration of hydrogen in the upper yard (or meter) of regolith, the loose surface material on Ceres. The color information is based on the number of neutrons detected per second by GRaND. Counts decrease with increasing hydrogen concentration. The color scale of the map is from blue (lowest neutron count) to red (highest neutron count). Lower neutron counts near the pole suggest the presence of water ice within about a yard (meter) of the surface at high latitudes.

Note that the data has not detected water. The blue areas on the image to the right suggest an increased amount of hydrogen, which could only be held to the surface if it was locked in some molecule, with water being the most likely candidate. Like the Moon, until we actual capture some samples, it will be difficult to confirm with certainty the presence of water.

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Vast Martian dune fields

11:01 am

Olympia Undae dune field

Cool image time! In the past few days the Themis camera on Mars Odyssey has taken two pictures of the vast Olympia Undae dune field near Mars’s north pole. The image to the right is only a cropped, lower resolution section of one of those images.

The image was taken during the summer, so most of the winter CO2 frost has sublimated away. Unfortunately, the website does not provide a scale, though they say the full images each cover about 12 by 43 miles of territory. Yet, both images capture only very tiny portions of the dune field, which apparently goes on and on for many hundreds of miles in all directions, looking exactly the same wherever you look.

Just imagine trying to travel though this area. It is the epitome of a trackless waste. And without some form of GPS system getting lost forever would be incredibly easy.

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New close-up of Occator Crater’s spots

1:57 pm

Occator Crater central spot

The Dawn science team have released new images taken from the spacecraft’s low orbit observations, including a close-up of the central white spot at Occator Crater, the brightest spot on Ceres.

The image on the right is a cropped though full resolution version of the full image. I have reduced it only slightly. As they note,

Occator Crater, measuring 57 miles (92 kilometers) across and 2.5 miles (4 kilometers) deep, contains the brightest area on Ceres, the dwarf planet that Dawn has explored since early 2015. The latest images, taken from 240 miles (385 kilometers) above the surface of Ceres, reveal a dome in a smooth-walled pit in the bright center of the crater. Numerous linear features and fractures crisscross the top and flanks of this dome. Prominent fractures also surround the dome and run through smaller, bright regions found within the crater.

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A new gravity map of Mars

9:06 am

Using data from three orbiting NASA spacecraft scientists have created a new gravity map of Mars, showing the subtle variations in its gravitational field due to density differences within the planet.

The improved resolution of the new gravity map suggests a new explanation for how some features formed across the boundary that divides the relatively smooth northern lowlands from heavily cratered southern highlands. Also, the team confirmed that Mars has a liquid outer core of molten rock by analyzing tides in the Martian crust and mantle caused by the gravitational pull of the sun and the two moons of Mars. Finally, by observing how Mars’ gravity changed over 11 years – the period of an entire cycle of solar activity — the team inferred the massive amount of carbon dioxide that freezes out of the atmosphere onto a Martian polar ice cap when it experiences winter. They also observed how that mass moves between the south pole and the north pole with the change of season in each hemisphere.

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The first geology map of Pluto

10:19 am

Geology map of Pluto

The New Horizons science team has now released the first geology map of a portion of Pluto, seen by the spacecraft during its fly-by last year.

It is definitely worth your while to take a look at the full image, along with the legend explaining the different surface features. Most of the geological terms are merely descriptive, but the careful breakdown still provides a much deeper understanding of what is there.

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A river on Mars

11:02 am

A river on Mars

Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter this week released it monthly set of cool images. One of those images, which I have cropped and reduced to show it here, is of an ancient river on Mars, the formation process of which geologists still debate. As the scientists note,

The channel pattern, called “dendritic” because of its tree–like branching, begins at the top of the image and runs down over the rim of an ancient impact basin across the basin floor. The soil surface overlying these channels, and indeed the entire landscape, has been changed and reworked over the intervening millions of years, by the combined actions of wind and ice. Over time, the original channels become muted or even erased.

One thing I learned in writing an article for Astronomy about the rivers seen on Saturn’s moon Titan is that without plant life there is no known natural process to hold river banks in place. Instead, if the grade is shallow and not confined by bedrock cliffs, rivers will meander about randomly forming braided channels as there will be nothing on shore to hold the water within the same course. For example, on a lifeless Earth the water draining the central basin of the midwest United States would have flowed south across a wide scattered area covering the entire plains, rather than flowing within the courses of the Missouri and Mississippi rivers.

Thus, it is not surprising that this river on Mars appears muted or partly erased. It probably was never very clearly delineated in the first place.

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Water unneeded to produce wet gullies on Mars

9:51 pm

The uncertainty of science: New modeling suggests that the wet gullies seen on Mars can be produced by dry ice, not water.

The theory is not completely new, but Cedric Pilorget and François Forget, with the University of Paris-Sud, and Paris’ Pierre and Marie Curie University, respectively, flesh out the idea with some hard numbers. Their new computer model calculates seasonal changes and impacts of an underlying layer of regolith, a carbon dioxide ice layer and the carbon dioxide-dominated gas atmosphere above. The simulation can take into account a variety of latitudes, slopes and other parameters.

The scientists found that most of the gullies could be created in a process that does not require any liquid water.

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A movie of Ceres

9:09 am

Cool movie time! The Dawn science team has released a movie compiled from images taken by the spacecraft, showing in false color the entire dwarf planet’s rotation as well as doing a fly-over of Occator Crater with its double bright spot.

I have posted the movie below the fold. The false colors illustrate the different materials so far detected on the surface, and help explain the nature and origin of the surface features.
» Read more

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Bright spots on Ceres likely salt deposits

1:56 pm

Based on an analysis of Dawn images scientists now believe that the bright spots on Ceres are salt deposits, not water ice.

Le Corre and colleagues, using images from Dawn’s framing camera, suggest that these salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt. “The location of some bright spots also coincide with places where water vapor was detected by other spacecraft,” said Reddy, a PSI Research Scientist. “This gives us confidence that the bright spots are likely salt deposits left over by sublimating salty water.”

While the bright spots themselves are not ice, they are what is left over after salty water evaporates.

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Scientists begin another attempt to drill through the Earth’s crust

9:26 am

An expedition to the Indian Ocean is about to begin an effort to drill a core down through the Earth’s crust and into its mantle.

Geologists have been trying to drill through the contact between the crust and the mantle, called the Moho, since the 1960s, with no success. Either the projects have gone way over budget and been shut down, have failed due to engineering problems, or were stopped by the geology itself. This last issue is maybe the most interesting.

Expeditions have come close before. Between 2002 and 2011, four holes at a site in the eastern Pacific managed to reach fine-grained, brittle rock that geologists believe to be cooled magma sitting just above the Moho. But the drill could not punch through those tenacious layers. And in 2013, drillers at the nearby Hess Deep found themselves similarly limited by tough deep-crustal rocks

This new project hopes to learn from these past problems to obtain the first rock samples from below the Earth’s crust.

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Earth’s magnetic field might not be flipping

10:12 pm

The uncertainty of science: A new analysis of the past strength of the Earth’s magnetic field suggests that today’s field is abnormally strong and that, even with the 10% decline in the field’s strength in the past two centuries, it remains stronger than the average over the past 5 million years.

The new data also suggests that the field might not be about to shut down and then reverse polarity, as some scientists have theorized based on the 10% decline. Instead, the data says that the field’s unusual strength today only means that the decline is bringing it back to its average strength, and is not necessarily an indication of a pending reversal.

To put it mildly, there are a lot of uncertainties here, including questions about the database that has been used previously by geologists to estimate the past strength of the Earth’s magnetic field. The database might have been right, but the new study raises significant new questions.

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Study questions scientific dating method

8:32 am

The uncertainty of science: A new study has raised questions about the methods scientists have used to date the late heavy bombardment in the early solar system.

A study of zircons from a gigantic meteorite impact in South Africa, now online in the journal Geology, casts doubt on the methods used to date lunar impacts. The critical problem, says lead author Aaron Cavosie, a visiting professor of geoscience and member of the NASA Astrobiology Institute at the University of Wisconsin-Madison, is the fact that lunar zircons are “ex situ,” meaning removed from the rock in which they formed, which deprives geoscientists of corroborating evidence of impact. “While zircon is one of the best isotopic clocks for dating many geological processes,” Cavosie says, “our results show that it is very challenging to use ex situ zircon to date a large impact of known age.”

The problem is that the removal of the zircon from lunar rocks changes the data enough to make the dating unreliable. The method might work on Earth, but the dating done on Apollo samples can be questioned. This means that much of the supposed history of the solar system, centered on what planetary scientists call the late heavy bombardment, a period 4 billion years ago when the planets were being hit by innumerable impacts as they cleared the solar system of its dusty debris disk, might not have happened as dated from lunar samples. If so, our understanding of when that bombardment ended and life began to form on Earth might be considerably incorrect.

The solution? Get to the planets in person, where you can obtain many samples in situ and thus gather a much deeper understanding of the geology.

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Back from a weekend underground

9:22 pm

Bob Zimmerman underground

The picture on the right will explain why I have been silent posting since Friday. I have just returned with five friends from three days of caving in New Mexico, doing some wild caving plus my first visit to Carlsbad Caverns since 1992, guided by a local caver who has been helping me with my cave survey project in Arizona.

New Mexico probably has the largest concentration of truly large and spectacularly decorated caves in the entire world. I’ve caved there previously, but this was my first trip driving from Arizona. We went to two wild caves, one of which I had never visited before and a second that I had seen during my 1992 trip. The picture shows me in the latter, standing above a large clear pool near the back of the cave with some giant flowstone speleothems all around me.

The new cave contained a room dubbed Speleogasm, because every formation there, of which there are too many to count, is completely festooned with helectites and sodastraws in a mad protrusion that no geologist can as yet explain. Nor is there any way to describe it adequately or photograph it successfully. To witness it you need to go, requiring the specialized caving skills that include the techniques and equipment required to rappel and climb a 40 foot rope.

As always, the advantages of learning how to do this successfully is the reward of seeing things that few ever see. It is why engineers and scientists strive so hard to get planetary probes to distant planets. And why humans want to travel to the planets. For me, getting inside a remote and beautifully decorated cave will just have to do.

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An avalanche on Mars, as it happens

4:49 pm

Avalanche on Mars

Cool image time! In their routine monitoring for avalanches at the layered deposits at the Martian north pole, the Mars Reconnaissance Orbiter science team captured the avalanche on the right, as it happened.

This picture managed to capture a small avalanche in progress, right in the color strip. … The small white cloud in front of the brick red cliff is likely carbon dioxide frost dislodged from the layers above, caught in the act of cascading down the cliff. It is larger than it looks, more than 20 meters across, and (based on previous examples) it will likely kick up clouds of dust when it hits the ground.

They note that avalanches in this area of Mars are common in the spring when things are warming, and have been documented previously, but possibly not so dramatically.

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Changes on the surface of Comet 67P/C-G

6:16 pm

In a science paper now accepted for publication, the Rosetta science team have described changes that have occurred on the surface of Comet 67P/C-G from May through July of this year as the comet moved closer to the Sun and activity increased.

The changes were seen in a smooth area dubbed Imhotep.

First evidence for a new, roughly round feature in Imhotep was seen in an image taken with Rosetta’s OSIRIS narrow-angle camera on 3 June. Subsequent images later in June showed this feature growing in size, and being joined by a second round feature. By 2 July, they had reached diameters of roughly 220 m and 140 m, respectively, and another new feature began to appear.

By the time of the last image used in this study, taken on 11 July, these three features had merged into one larger region and yet another two features had appeared.

Be sure to click on the link to see the images. The changes look like a surface layer is slowing evaporating away.

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Petrified sand dunes on Mars

11:09 am

Petrified sand dunes on Mars

Cool image time! A panorama produced from images taken by Curiosity’s Mast camera has revealed the remains of ancient sand dunes, cemented into sandstone and now eroding.

This sandstone outcrop — part of a geological layer that Curiosity’s science team calls the Stimson unit — has a structure called crossbedding on a large scale that the team has interpreted as deposits of sand dunes formed by wind. Similar-looking petrified sand dunes are common in the U.S. Southwest. Geometry and orientation of the crossbedding give information about the directions of the winds that produced the dunes.

The Stimson unit overlies a layer of mudstone that was deposited in a lake environment. Curiosity has been examining successively higher and younger layers of Mount Sharp, starting with the mudstone at the mountain’s base, for evidence about changes in the area’s ancient environment.

The image above is cropped and reduced in resolution. Be sure to look at the original.

This report also suggests that Curiosity is definitely moving up the geological layers on Mount Sharp. With each layer, we learn a little bit more about the complex geological history of Gale Crater.

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Martian floods regional, not global

5:52 pm

Using the data accumulated from various modern Mars orbiters scientists now think that many of the Martian floods were caused by regional circumstances rather than a single global event.

“The flooding is due to regional processes, not global processes,” said Rodriguez, a Senior Scientist at the Planetary Science Institute and lead author of “Martian outflow channels: How did their source aquifers form, and why did they drain so quickly?” that appears in a Nature Scientific Report. “Deposition of sediment from rivers and glacial melt filled giant canyons beneath a primordial ocean contained within the planet’s northern lowlands. It was the water preserved in these canyon sediments that was later released as great floods, the effects of which can be seen today.”

The canyons filled, the Martian ocean disappeared, and the surface froze for approximately 450 million years. Then, about 3.2 billion years ago, lava beneath the canyons heated the soil, melted the icy materials, and produced vast systems of subterranean rivers extending hundreds of kilometers. This water erupted onto the now-dry surface in giant floods.

This theory suggests that Mars still has a great deal of trapped frozen water held in large underground reserves, available for future colonists. I like the fact that it also suggests that there were “vast systems of subterranean rivers extending hundreds of kilometers” where this frozen water was once stored and, having now melted, has left behind gigantic underground caverns.

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Curiosity spots a spoon on Mars!

9:04 am

The spoon on Mars

Very cool image time! In one of Curiosity’s recent images of the Martian surface on the slopes of Mount Sharp appears what looks like a long thin spoon jutting horizontally out of the ground.

The shadow below the feature is strong evidence that that this almost certainly a real object, shaped exactly as we see it. However, it is not an artificially created spoon. If you look at both the full raw image as well as zoom in on the feature itself, you will see that it is something that formed naturally due to Mars’ low gravity and the geology here. The spoon is a thin prong of harder material that has remained intact as the ground below it has been slowly eroded away by the ever-present but very weak Martian wind. If you look close you can see that harder material extend back into the rock behind the spoon.

Some of that erosion might also have been caused by flowing water sometime in the past, but to confirm this will take additional geological research.

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Largest glacier calving event ever filmed

6:01 pm

An evening pause. Hat tip Phill Oltmann. I had sworn I had posted this already, but now can’t find it on BtB. And even if I have posted it, it is worth watching again. My only comment is that I am baffled by the film’s description of the event as “horrifying.” I don’t find this natural event horrifying, I find it awe-inspiring. It reminds us that the scale of the universe if far far beyond anything we can imagine.

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Comet 67P/C-G’s fractured surface

8:49 am

Rosetta scientists today published a paper describing the many different types of fractures they have identified on the surface of Comet 67P/C-G.

Ramy’s team identified three distinct settings in which the fractures occur: networks of long narrow fractures, fractures on cliffs and fractured boulders. In addition, several unique features were identified: the parallel fractures running across Hathor’s 900 m-high cliffs, an isolated 500 metre-long crevice in the Anuket region of the comet’s neck, and a 200 m-long complex crack system in Aker on the large lobe. “The fractures show a variety of morphologies and occur all over the surface and at all scales: they are found in the towering 900 m-high cliffs of Hathor right down to the surfaces of boulders a few metres across,” describes lead author M. Ramy El-Maarry from the University of Bern.

The most prevalent setting appears to be networks of narrow fractures that extend for a few metres to 250 m in length, typically on relatively flat surfaces. Interestingly, in some locations, the fractures appear to cross cut each other in polygonal patterns at angles of 90º – on Earth and Mars this is often an indicator of ice that has contracted below the surface.

While their focus is on the geology of the comet and its development as indicated by the fractures, what I see is the root cause of the comet’s eventual destruction. Its two-lobed shape is inherently unstable, and these fractures illustrate this. At some point, the comet will break apart. The fractures indicate where the first breaks might occur.

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