Search Results for: transition zone

Fractured and collapsed Martian crater floor

Fractured and collapse Martian crater floor
Click for full image.

Time for some puzzling Martian geology. The image on the right, rotated, cropped, and reduced to post here, comes from the Mars Reconnaissance Orbiter (MRO) high resolution archive, and shows a strangely collapsed and fractured crater floor. In fact, like a number of other Martian craters, rather than having a central peak, the center of the crater floor, shown at the image’s center right, seems depressed.

The crater is located in a region dubbed the Cerberus Plains, in a hilly subregion called Tartarus Colles. Of the transition zone between the northern lowlands and the southern highlands these plains comprise the second largest region.

Being in the transition zone I would guess that the geology here is strongly influenced by the ebb and flow of the slowly retreating intermittent ocean that is thought to have once existed in the nearby lowlands. As water came and went, it created a variety of shoreline features scattered about, but not in a single sharp line as we would expect on Earth. Think more like tidal pools, where in some areas water gets trapped and left behind only to sublimate away at at later time.

We can see some hints of these processes in the images of the floors of two other craters that I have previously highlighted, here and here.

With this geological overview in mind, the broken plates here remind me of features I’ve seen in caves. Mud gets washed into a passage, partly filling it. Over time a gentle water flow over the surface of the mud deposits a crust of calcite flowstone on top of the mud. Should the water flow suddenly increase, it will wash out the mud below the crust. If the crust is not very strong or thick, it will crack into pieces as it falls, and thus resemble what we see here in this Martian crater.

There are cases where the crust becomes thick enough to remain standing, which produces some spectacular hanging calcite draperies that seem to defy explanation.

The collapse in the center of the crater is more puzzling, but suggests, based on comparable-looking Earth geology, that any perched water in this canyon might have actually drained out through underground drainage, accessed through the depression.

Be warned: All my explanations above are based on what exists on Earth, and Mars is very different from Earth. The lower gravity, colder temperatures, and different chemistry guarantee that the geological processes there will not be identical. We start by using what we know here, but recognize that we need to learn more about Mars to truly understand what goes on there.


The many pits of Arsia Mons

The many pits of Arsia Mons

When it comes to Mars, it appears that if you want to find a pit that might be the entrance to an underground system, the place to look is on the slopes of Arsia Mons, the southernmost volcano in the chain of three giant volcanoes between Olympus Mons to the west and the vast canyon Marineris Valles to the east.

To the right is an overview map showing the pits that have been imaged since November by the high resolution camera of Mars Reconnaissance Orbiter (MRO). The black squares show the pits that I highlighted in previous posts on November 12, 2018, February 22, 2019, and April 2, 2019. The numbered white squares are the new pits found in March photograph release from MRO.

And this is only a tiny sampling. Scientists have identified more than a hundred such pits in this region. Dubbed atypical pit craters by scientists, they “generally have sharp and distinct rims, vertical or overhanging walls that extend down to their floors, surface diameters of ~50–350 m, and high depth to diameter (d/D) ratios” that are much greater than impact craters, facts that all suggest that these are skylights into more extensive lava tubes.

Below are the images of today’s four new pits.
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Jezero Crater: The landing site for the Mars 2020 rover

Jezero Crater delta
Jezero Crater delta

At this week’s 50th Lunar and Planetary Science Conference in Texas, there were many papers detailing the geological, topographical, chemical, meteorology and biological circumstances at the landing sites for the 2020 Martian rovers, Jezero Crater for the U.S.’s Mars 2020 and Oxia Planum for Europe’s Rosalind Franklin.

Most of these papers are a bit too esoteric for the general public (though if you like to delve into this stuff like I do, go to the conference program and search for “Jezero” and “Oxia” and you can delve to your heart’s content).

Oxia Planum drainages

These papers do make it possible to understand why each site was chosen. I have already done this analysis for Rosalind Franklin, which you can read here and here. Oxia Planum is in the transition between the southern highlands and the northern lowlands (where an intermittent ocean might have once existed). Here can be found many shoreline features. In fact, one of the papers at this week’s conference mapped [pdf] the drainage patterns surrounding the landing ellipse, including the water catchment areas, as shown by the figure from that paper on the right.

With this post I want to focus on Jezero Crater, the Mars 2020 landing site. The image above shows the crater’s most interesting feature, an impressive delta of material that apparently flowed out of the break in the western wall of the crater.

This image however does not tell us much about where exactly the rover will land, or go. To do that, we must zoom out a bit.
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Mars likely has many large and extensive cave systems

Mamers Valles

More caves on Mars! This week the Lunar and Planetary Institute and the Johnson Space Center are jointly holding the 50th Lunar and Planetary Science Conference in Texas. I have been going over the program, and will be posting reviews of some of the more interesting results all this week.

We begin with caves, which should not be surprising to my regular readers. As a caver who also knows their value for future space colonists, I am always attracted to new discoveries of cave passages on other worlds. Today’s however is a doozy.

The image to the right is of Mamers Valles on Mars, what scientists have dubbed a fretted valley, a common feature in the transition zone between the low altitude northern plains and the southern highlands. It comes from a paper [pdf] with the typically unexciting scientific title, “Fretted channels and closed depressions in northern Arabia Terra, Mars: Origins and implications for subsurface hydrologic activity.”

What the scientists really means here is that their research strongly suggests that Mars has a very large and very extensive number of underground drainage systems, which have caused collapses on the surface that often resemble meandering river canyons, such as seen above. As they explain:
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New analysis supports catastrophic floods and intermittent ocean on Mars

The intermittent ocean at the outlet to Marineris Valles

A new analysis of Martian data once again suggests that an intermittent ocean once existed in the planet’s northern hemisphere, and that it was fed by catastrophic floods coming down from the volcanoes through Marineris Valles.

“Our simulation shows that the presence of the sea would have attenuated cataclysmic floods, leading to shallow spillovers that reached the Pathfinder landing site and produced the bedforms detected by the spacecraft,” said [lead scientist Alexis Rodriguez].

The team’s results indicate that marine spillover deposits contributed to the landscape that the spacecraft detected nearly 22 years ago, and reconcile the mission’s in situ geologic observations and decades of remote-sensing outflow channel investigations.

The sea bears an uncanny resemblance to the Aral Sea on Earth in that in both instances they lack distinct shoreline terraces. Its rapid regression over shallow submerged slopes resulted in rates of shoreline front retreat too fast for the terraces to form. The same process could partly account for the long-recognized lack of northern plains shorelines.

“Our numerical simulations indicate that the sea rapidly became ice-covered and disappeared within a few thousand years due to its rapid evaporation and sublimation. During this time, however, it remained liquid below its ice cover,” said PSI Senior Scientist Bryan Travis, a co-author in the paper.

The map above shows the outlet region to the west and north of Marineris Valles. (The paper from which it is adapted is available on line here.) It shows that inland sea, created by the catastrophic floods. Because it sits at a lower elevation than the plains to the north, the floods that entered it ponded there, where they dried up. Only when the floods were at their highest did the water spill out into the northern plains.

In reading the paper, it confirms many of the suppositions I myself have made in my frequent posts analyzing numerous Mars Reconnaissance Orbiter (MRO) images, such as the lack of a clear shoreline because the ocean was short-lived. As it dried up its edge left patches of shoreline, at different elevations and in pondlike patterns, almost like the beach debris left behind by the tide.

The paper also shows that some of my guesses were not quite correct. For example, this new analysis says that the catastrophic floods only partly carved out the chaos terrain of Hydraotes Chaos, rather than do it all as I supposed here. Instead, the floods contributed, but much of the erosion occurred when the short-lived inland sea existed here, eroding away at the mesas from all sides.

Read it all. Though this remains a simulation based on what is presently very incomplete data and thus has many uncertainties, it will give you a much deeper understanding of what we presently theorize about the past geological history of Mars.


Brain Terrain on Mars

Brain terrain on Mars
Click for full image.

Cool image time! This week the Mars Reconnaissance Orbiter (MRO) science team featured four new captioned images taken by the spacecraft and released as part of the March image dump. The first, dubbed “The Slow Charm of Brain Terrain,” deserves an immediate post on Behind the Black. To the right is only a small section cropped from the full image. From the caption:

You are staring at one of the unsolved mysteries on Mars. This surface texture of interconnected ridges and troughs, referred to as “brain terrain” is found throughout the mid-latitude regions of Mars. (This image is in Protonilus Mensae.)

This bizarrely textured terrain may be directly related to the water-ice that lies beneath the surface. One hypothesis is that when the buried water-ice sublimates (changes from a solid to a gas), it forms the troughs in the ice. The formation of these features might be an active process that is slowly occurring since HiRISE [MRO’s high resolution camera] has yet to detect significant changes in these terrains.

Below is a cropped section of the full image, rotated and reduced to post here.
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Waterlike Martian lava flows

Flowing like water
Click for full image.

Each month the Mars Reconnaissance Orbiter (MRO) science team highlights with captions about four out of the 300-500 new images released that month.

Of the four captioned images in February, the first was entitled “Almost Like Water,” and focused on the waterlike nature of the lava flow. The image on the right is a cropped and annotated section of that featured photograph, with the yellow arrows indicating the flow directions.

The lava appears to have flowed smoothly around obstructions, almost like water, forming streamlined islands. In the southern part of this image, a branch of the flow diverts around a small crater, and eventually rejoins the main part of the flow. [Visible in the full photograph] Irregular-shaped ring structures appear on the northern end and are related to the volcanic activity that formed the flows.

You can see an example of one of those islands near the top of the above image.

This is hardly the only MRO image showing such flows. In fact, the February image release included a bunch, some of the more intriguing of which I highlight below. These lava flows are seen in many different places on Mars, in a wide variety of geological settings, facts that suggest that volcanic activity was once very widespread and ubiquitous on Mars.
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Monitoring a fresh-looking Martian landslide

2012 image of Martian landslide
Click for full image

2018 image of Martian landslide
Click for full image

Time for two cool images! To the right are two images taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO), the top one taken in April 2012, and the bottom taken in December 2018. Both have been cropped and reduced slightly in resolution to post here.

The second image is trying to answer, in only a small way, one of the most fundamental questions of the Martian environment: How fast does it change? The images from orbit have periodically seen evidence of new impacts. MRO images have tracked dust devil tracks. And we know that somehow water, ice, wind and volcanic activity have eroded and reshaped the surface over eons.

What we don’t know truly and with detail is the pace of these changes, with any accuracy. The pace of some things over time seems obvious. For example, Mars’s inactive but gigantic volcanoes suggest that once volcanism was very active, but over time has ceased so that today it is unclear if any is occurring. Similarly, the geological evidence suggests that in the far past water flowed on the surface, producing catastrophic floods. Now that liquid water is all but gone, and this erosion process as ceased.
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Flowing cracked mud on Mars?

mud cracks in crater?

Cool image time! The image on the right, rotated, cropped, and reduced to post here, comes from the December image release of the high resolution camera of Mars Reconnaissance Orbiter (MRO. Uncaptioned, the release titles this image “Cracks in Crater Deposit in Acheron Fossae.” If you click on the image you can see the entire photograph at full resolution.

Clearly the cracks appear to be caused by a downward slumping to the north, almost like a glacier made of mud. We can also see places on the image’s right edge where the mud appears to have flowed off a north-south trending ridge, then flowed downhill to the north. All of this flow is away from the crater’s central peak, which is only partly seen in the photograph near the bottom. That section is the central peak’s southwestern end, with the whole peak a ridge curving to the northeast beyond the edge of the image.

At the north edge of this mud flow the cracks become wider canyons, as if long term erosion is slowing washing the mud away. The flow then stair steps downward in a series of parallel benches. Meanwhile, in the flat central area of the mud flow above can be seen oblong depressions suggesting sinks that also flow to the north.

crater context overview

You can get a better idea of the crater’s overall floor and central peak by the low resolution context image to the right. The white rectangular box indicates the area covered by the full image above. A close look at this part of the crater floor suggests to me a circular feature like a faint eroded smaller crater that includes as its eastern rim the larger crater’s central peak. This impression suggests that the flows seen in the full resolution image are heading downhill into the lowest point of this smaller crater, that upon impact had reshaped the larger crater’s floor.

This impression however is far from conclusive. The features in the large crater could simply be the random geology that often occurs in the floors of impact craters.

What makes this particular mud slide most interesting, as is usually the case for most Martian terrain, is its location.
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Dried mud cracks on Mars?

Mud cracks on Mars?

Cool image time! The image to the right, cropped and rotated to post here, was one of the uncaptioned photographs in the December Mars Reconnaissance Orbiter (MRO) image release. If you click on the image you can see the entire photograph. I have cropped the most interesting area, though cracks can be seen in other areas in the image.

What we appear to have here is a darker lower valley filled with dried mud, which over time has cracked as it dried. At its edges there appear to be ripples, almost like one sees on the beach as waves wash the shore. The perimeter slopes even show darker streaks as if the water in some places lapped up the slopes, and in others flowed downward into the valley.

Later, several meteorite impacts occurred, the largest of which produced concentric dried cracks on its outside perimeter. This impact also provides a rough idea of the depth of the mud in this valley.

Mud of course suggests that this lower valley once was filled with water. Was it? It is not possible now to come to a firm conclusion, but this image’s location shown by the red dot in the overview map below and to the right, provides a clue that strengthens this hypothesis.
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Dark dunes, wedding cake mesas, and dust-filled gullies

Dark dunes, wedding cake mesas, and dust-filled gullies

Cool image time! The photo on the right, reduced, rotated, and cropped slightly to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and issued by the spacecraft science team in its December image release.

They didn’t give this image a caption. The release title, “Arabia Terra with Stair-Stepped Hills and Dark Dunes,” significantly understates the wild variety of strange features throughout this terrain. Normally I crop out one section of the photographs I highlight to focus on the most interesting feature, but I couldn’t do it this time. Click on the image to see the full resolution version. Take a look at the complex wedding cake mesas in the lower left. Look also at the streaks of dust that I think are filling the gullies between these hills. In the image’s upper left are those dark dunes, scattered between dust ripples and small indistinct rises and what appears to be a drainage pattern descending to the north. Interspersed with these dunes near the center of the image are several perched crater floors, indicating that the crater impacts happened so long ago that the surrounding terrain had time to erode away, leaving the crater floor hanging like a small plateau.

On the right the two largest mesas rise in even stair-stepped layers that would do the mesas in the Grand Canyon proud.

This could very well be the coolest image I have ever posted. Everywhere you look you see something different, intriguing, and entirely baffling.

Arabia Terra covers the largest section of the transition zone between Mars’s high cratered south and its low flat northern plains, where some scientists believe an intermittent ocean might have once existed. It lies to the east of Valles Marineris, and is crater-filled with numerous intriguing geology, as this image most decidedly illustrates. In this particular case it shows the floor of one of the region’s mid-sized craters.


The vast southern highlands of Mars

Small section of Rocky Highlands

Rocky highlands

Cool image time! This week the Mars Reconnaissance Orbiter (MRO) science team made available its monthly release of new images taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The image above is just a small cropped section from one of those new images, released under the name “Rocky Highlands.” The image on the right is a cropped and reduced section of the full photograph, with the white box indicating the small section above. If you click on either you can see the full resolution uncropped photograph and explore its complex and rough terrain.

What should immediately strike you looking at the small inset section above is the difficulty anyone is going to have traversing this country. There are no flat areas. Every inch seems to be a broken and shattered collection of ridges, pits, craters, or rippled dunes. And the inset above is only a tiny representation of the entire image, all of which shows the same kind of badlands.

This forbidding place is located in the southern highlands of Mars, north of Hellas Basin and south of the transition zone that drops down to the northern lowland plains. The white cross on the map below indicates the image location, with green representing the transition zone, blue the northern plains, and red/orange the southern highlands..
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Present and future landing sites on Mars

With InSight’s landing on Mars set for 11:54 am (Pacific) this coming Monday, November 26, 2018, I decided to put together a map of Mars showing the location of all the successful landers/rovers, adding the landing sites for the planned landers/rovers through 2020. This will give some context to InSight’s landing site.

Landing sites on Mars

The map does not show the landing sites for the failed Soviet, American, and British landers.

As I noted in describing the Mars2020 landing site, the location of the bulk of these landing sites, along the transition zone from the southern highlands and the northern lowlands, demonstrates the areas of the planet that interest geologists the most. It is here that we find many shoreline features, suggestive of the ocean that many scientists theorize existed intermittently in the northern lowlands. It is here that planetary scientists can quickly gather the most information about Martian geological history. And it is here that they have the opportunity to study the widest range of rock types.

From an explorer’s perspective, however, this approach has its limits. It does not provide us a look at a wide variety of locations. It is not directly aimed at finding lower latitude locations where ice might actually exist. And it is decidedly not focused in studying the planet from the perspective of future colonists. I am sometimes frustrated that we have as yet no plans to send any rovers into Marineris Valles, or to the western slopes of Arsia Mons, the southern most volcano in the chain of three giant volcanoes where there are indications that ice might exist underground, or to any of the places where caves are known to exist where a colony could be built more easily. In fact, the caves on the slopes of Arsia Mons seems a prime exploration target.

Eventually these locations will be explored, likely by private landers aimed at scouting out locations for future private settlements. I am just impatient.


NASA picks Mars 2020 landing site: Jezero Crater

Jezero Crater

NASA has picked Jezero Crater has the landing site for its as yet unnamed 2020 Mars rover.

Jezero Crater is located on the western edge of Isidis Planitia, a giant impact basin just north of the Martian equator. Western Isidis presents some of the oldest and most scientifically interesting landscapes Mars has to offer. Mission scientists believe the 28-mile-wide (45-kilometer) crater, once home to an ancient river delta, could have collected and preserved ancient organic molecules and other potential signs of microbial life from the water and sediments that flowed into the crater billions of years ago.

Jezero Crater’s ancient lake-delta system offers many promising sampling targets of at least five different kinds of rock, including clays and carbonates that have high potential to preserve signatures of past life. In addition, the material carried into the delta from a large watershed may contain a wide variety of minerals from inside and outside the crater.

The geologic diversity that makes Jezero so appealing to Mars 2020 scientists also makes it a challenge for the team’s entry, descent and landing (EDL) engineers. Along with the massive nearby river delta and small crater impacts, the site contains numerous boulders and rocks to the east, cliffs to the west, and depressions filled with aeolian bedforms (wind-derived ripples in sand that could trap a rover) in several locations.

The red dot on the map of Mars below shows this location. The blue dot is Gale Crater where Curiosity landed. The purple dot is the landing site for the European ExoMars rover. The yellow dot is where Opportunity has been roving, and the black dot is Spirit’s location.
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Volcanic rivers on Mars

Granicus Valles

Cool image time! The photo on the right, cropped and reduced to post here, was part of the November image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO). If you click on the image you can see the full resolution picture.

The uncaptioned release webpage is dubbed “Faults in Granicus Valles.” The image itself only shows a small part of Granicus Valles, named after a river in Turkey, that flows down from the estern slopes of the giant volcano Elysium Mons. While far smaller than the four big Martian volcanoes in the Tharsis region to the east and near Marines Valles (which I highlight often), Elysium Mons still outshines anything on Earth at a height of almost 30,000 feet and a width of 150 miles. It sits at about the same northern latitude of Olympus Mons, but all by itself, rising up at the very northern edge of the transition zone between the southern highlands and the northern plains, with the vast Utopia Basin, the second deepest basin on Mars, to the west.

Overview of Elysium Mons and Granicus Valles

Granicus Valles itself is almost five hundred miles long. At its beginning it flows in a single straight fault, but once it enters the northern plains of Utopia Basin it begins to meander and break up into multiple tributaries. The MRO image above shows only a tiny portion in the northern plains, as illustrated by the white box in the overview map to the left.
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The ExoMars 2020 landing site

ExoMars 2020 landing site

Last week the European Space Agency (ESA) announced the final chosen landing site for their 2020 ExoMars rover, a region called Oxia Planum.

Since then they have posted several detailed overview maps describing this region. The image on the right, reduced slightly to post here, shows the final two candidate elliptical landing sites in black, with Oxia Planum on the left. The caption for this image adds this tantalizing detail:

Both landing site candidates lie close to the transition between the cratered northern highlands and the southern lowlands of Mars. They lie just north of the equator, in a region with many channels cutting through from the southern highlands to the northern lowlands. As such, they preserve a rich record of geological history from the planet’s wetter past, billions of years ago.

To understand better what they mean by this, we need to zoom out.
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Another skylight entrance pit found on Mars

Pit in Hephaestus Fossae

Cool image time! In my routine monthly review of the hundreds of new images released from the high resolution camera on Mars Reconnaissance Orbiter (MRO), I came across another most intriguing geological feature, the image of which is posted to the right, after cropping.

As the scale shows, the pit is about 300 feet across. Calculating the pit’s depth would require someone with better math skills than I. The website provides information about the sun angle, which can be used to extrapolate the shadows and then roughly calculate the depth.

The most fascinating aspect of this pit is the impression of incredible thinness for the pit’s overhung edges. All of the pit’s edges appear significantly overhung, and the thickness of the overhang seems incredibly paper-thin. This thinness is likely only an illusion, though in Mars’s light gravity it is perfectly possible for the overhang to be far thinner and more extended than anything you would find on Earth.

The image itself is in color, though the only color visible is within the pit itself. In that blueness at the base it seems to me that there is a pile of dust/debris, but once again, that conclusion should not be taken very seriously.

If you take a look at the full image, what is impressive is the bland flatness of the surrounding terrain. There is no hint that there might be underground passages hidden here. While most of the scattered craters are probably impact craters, many (especially those with unsymmetrical shapes) could be collapse features indicating the presence of underground voids. None however is very deep. Nor is there any other pits visible.

Below is a global map of Mars with the location of this pit indicated by a black cross. It is just on the edge of the transition zone between the lower northern plains and the southern highlands, where the shoreline of an intermittent sea is thought by some scientists to have once existed. This is also an area where not a lot of high resolution images have been taken, mostly because of its apparent blandness as seen in previous imagery.

This image demonstrates however that Mars is going to have interesting geology everywhere, and that we won’t really know it well until we have explored it all.
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Mars 2020 gets fourth candidate landing site

The science team for the next American Mars rover, Mars 2020, has decided to consider a fourth candidate landing site, located between two other candidate sites.

The site has been dubbed “Midway,” because it’s roughly halfway between two other candidate landing locations — Jezero delta and Northeast Syrtis. The third previously identified candidate is the Columbia Hills region of Gusev Crater, which NASA’s now-defunct Spirit rover explored after touching down in January 2004.

Jezero, Northeast Syrtis and Columbia Hills were selected as finalists at the third 2020 rover landing site workshop, which was held in February 2017.

Midway has the same morphologic units as Northeast Syrtis and is relatively close to Jezero, explained John Mustard, a professor in the Department of Earth Environmental and Planetary Sciences at Brown University in Providence, Rhode Island. “It has emerged from Mars 2020 science team members I believe brainstorming on possibly getting two birds with one rover,” Mustard told Inside Outer Space.

Based on this story, it sounds to me as this new site has emerged as the favorite. It would put the rover down in the transition zone between Mars’s northern low plains and its southern highlands, an area where evidence of the receding shoreline of any past intermittent ocean might exist. It would also allow it to study geology similar to two previous candidate sites.

One problem they may have is that this candidate site has not yet been photographed in detail by Mars Reconnaissance Orbiter’s (MRO) high resolution camera, as have the other sites. They will need to get time on MRO to do this in order to make sure this site is acceptable.


The mysterious chaos terrain of Mars

In one of my weekly posts last month (dated May 14th) delving into the May image release from Mars Reconnaissance Orbiter’s (MRO) high resolution camera, I featured an image of what planetary geologists have labeled chaos terrain, a hummocky chaotic terrain that has no real parallel on Earth but is found in many places on Mars.

This month’s image MRO release included two more fascinating images of this type of terrain. In addition, the Mars Odyssey team today also released its own image of chaos terrain, showing a small part of a region dubbed Margaritifer Chaos. Below, the Mars Odyssey image is on the right, with one of the MRO images to the left. Both have been cropped, with the MRO image also reduced in resolution. The full MRO image shows what the MRO science team labels “possibly early stage chaos” on the rim of a canyon dubbed Shalbatana Vallis.

young chaos in Shalbatana Vallis

Margaritifer Chaos

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The two candidate landing sites for ExoMars2020

The June release of new images from Mars Reconnaissance Orbiter (MRO) included three images of the two candidate landing sites for Europe’s 2020 ExoMars rover mission. All three images provide us as hint at what that rover might see when it arrives a few years from now.

ExoMars 2020 landing sites

The two candidate sites are locations on Mars dubbed Mawrth Vallis and Oxia Palas. The map to the right shows their general location to the east of Mars’s giant volcanoes and giant canyon Valles Marineris. The red splotches indicate the large number of images taken by MRO of these locations, partly to help the ExoMars science team choose which site to pick and partly to study the geology in these Martian locations. As you can see, both candidate sites are in the transition zone between the northern low plains and the southern highlands.

At first glance Mawrth Vallis seems the more spectacular site. Mawrth (Welsh for Mars) is one of the gigantic drainage canyons near Valles Marineris. Though tiny in comparison to Valles Marineris, on Earth it would easily rival the Grand Canyon in size, and in fact is slightly longer (400 miles versus 300 miles). Unlike the Grand Canyon, however, Mawrth Vallis doesn’t appear to have a distinct or obvious rim. This video, produced by the European Space Agency using images from its Mars Express orbiter, gives a sense of the canyon’s terrain as it flies upstream from the northern lowlands to the canyon’s high point in the southern highlands. The highlands on either side of the canyon more resemble the broken geology of Mars’s chaos regions that are found scattered about in this transition zone than the flat generally level Kaibab plateau that surrounds the Grand Canyon.

Mawrth Vallis

The image on the right is a tiny crop from the most recently released MRO image. The full image shows a strip of the upper plateau south of canyon and near its inlet from the southern highlands. This crop reveals a surface that is a wild mixture of colors and complex geology. In fact, in a 2017 MRO image release showing a different place in Mawrth Vallis, the canyon was dubbed a “painted desert.” To quote that release:

The clay-rich terrain surrounding Mawrth Vallis is one of the most scenic regions of Mars, a future interplanetary park. …The origin of these altered layers is the subject of continued debates, perhaps to be resolved by a future rover on the surface. We do know that these layers are very ancient, dating back to a time when the environment of Mars was wetter and more habitable, if there were any inhabitants.

Other MRO images of Mawrth Vallis here and here emphasize this description.

As for Oxia Palas, the other candidate landing site for ExoMars 2020, in the June MRO image release there were two images.
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Alien world

Meridiani Planum
So what is it we are looking at in the image above? I have reduced the resolution slightly to fit it here, but you can see the full resolution image by clicking on the picture.

Is it a marble or granite kitchen counter? Nah, the surface is too rough.

Maybe it’s a modern abstract painting that we can find hanging in the Museum of Modern Art in New York. Nah, it has too much style and depth. Abstract art is much more shallow and empty of content.

Could it be a close-up of a just-opened container of berry-vanilla ice cream, the different flavors swirling and intertwined to enhance the eating experience? No, somehow it looks too gritty for ice cream.
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Imaging restrictions on Mars Reconnaissance Orbiter

Young lava flows on Mars

In releasing a new set of four captioned images today from the high resolution camera on Mars Reconnaissance Orbiter (MRO), the captions from each also included this paragraph:

Note: HiRISE has not been allowed to acquire off-nadir targeted observations for a couple of months due to MRO spacecraft issues, so many high-priority science objectives are on hold. What can be usefully accomplished in nadir mode is sampling of various terrains. Especially interesting in this observation are bedrock exposures, which provide information about the geologic history of Mars. “Nadir” refers to pointing straight down.

The image restrictions are probably related to either or both the battery and and reaction wheel issues noted in recent status report. What it means is that though they can still take good and revealing images, like the one to the right, cropped and reduced to post here, showing very young lava flows only a few million years old, scientists have less flexibility in what they can photograph.

If you click on the image you can see the full resolution version. The reason scientists think these are young flows is that they are so few craters here. The lava flows are located in the southern lava flows coming off the large volcano Elysium Mons, which sits due west of Mars’ largest volcano, Olympus Mons. These flows are also in the transition zone between Mars’ low flat northern plains and its high rough southern terrain.

When and if the spacecraft can resume full imaging operations is unknown. Based on the status report, it might never do so.


Is it a volcano or an impact crater? Mars Express wants to know!

Europe’s Mars Express orbiter has taken a high resolution image of Ismenia Patera, a very large crater located in the Arabia Terra region of Mars, the largest part of the transition zone between the low flat northern plains and the high rough southern terrain.

The crater is intriguing to scientists because they are not sure if it was created by an impact, or a volcano.

Certain properties of the surface features seen in Arabia Terra suggest a volcanic origin: for example, their irregular shapes, low topographic relief, their relatively uplifted rims and apparent lack of ejected material that would usually be present around an impact crater.

However, some of these features and irregular shapes could also be present in impact craters that have simply evolved and interacted with their environment in particular ways over time.

There is also additional evidence that this region was once home to volcanic activity. If so, that activity would have changed the terrain, and thus made its geological history more complex and difficult to decipher, a fact that is important since this is also a region that might have been at the edge of theorized northern Martian Ocean.


Near the Martian shoreline

One of the prime areas of research for Mars planetary geologists is the region on Mars where the geography appears to transition from the southern cratered, rough terrain to the northern low, generally smooth, and flat plains. It is theorized by some scientists that the northern plains were once an ocean, probably shallow and probably intermittent, but wet nonetheless for considerable periods. The global map of Mars below, created by the laser altimeter on Mars Global Surveyor, clearly shows the obvious elevation differences between the low northern plans (blue) and the high, more cratered southern regions (changing from yellow to orange as you move higher).

Labeled global Map of Mars

Scientists have spent a considerable effort studying this transition zone (green on the map), illustrated by just one example I recently highlighted, showing that, though there does not appear to be a clear shoreline in many places, there is strong evidence that a shallow ocean repeatedly rose and fell in this transition zone, leaving behind geological ripple marks vaguely reminiscent of those seen on a beach caused by the rise and fall of the tides.

Today we highlight another example, taken in January 2018 at the location indicated by the cross on the above map.
» Read more


More weird Mars geology

Low resolution of full image of crater

Cool image time! Yesterday the Mars Reconnaissance Orbiter team released 460 images taken by the spacecraft’s high resolution camera, HiRISE, as part of their normal and routine image release program. Obsessed with space exploration as I am, I like to scan through these new images to see if there is anything interesting hidden there that will show up eventually in a press release. For example, the first image in this release is a look at Vera Rubin Ridge and Curiosity. I would not be surprised if there is a press release soon using this image, probably aimed at outlining the rover’s future route up Mount Sharp. (The present overview traverse map is getting out of date.)

Sometimes however I find images that might never get a press release but probably deserve it. The image on the right, reduced in resolution to show here, is one such example. It is a strip taken from rim to rim across an unnamed crater located in the mid-northern latitudes of Mars, west of Olympus Mons. A review of past images by other Mars orbiters/probes suggests that no good high resolution image of this crater had ever been taken before.

If you click on the image on the right, or go to the actual image site, you can see the original in full resolution. It is definitely worthwhile doing this, because the strip shows some strange and inexplicable geology on the floor of the crater as well in its confusing central peak region. Numerous features appear to have been exposed by later erosion. The many small craters for example are I think what planetary geologists call pedestal craters. The surrounding terrain is less erosion-resistant, so as that terrain erodes away it leaves the crater behind, with its floor actually sitting higher than the surrounding flats.

What makes these craters even weirder however is that their rims appear to have eroded away even more than the surrounding terrain, so that all of these small craters (assuming that is what they are) have ringlike depressions surrounding a circular platform.

In the crater’s central peak region the terrain is even more strange. Sticking up out of the ground are some arched short ridgelines, which appear to have been exposed by erosion. That peak area however also has many strange flow features that I find completely baffling. It almost appears to me that as the molten peak area started to solidify after impact, someone went in with a stirring spoon and did some mixing!

The map below the fold provides the location context for this crater, with the crater’s location indicated by the arrow.
» Read more


Wind eating away the Martian terrain

Yardangs on Mars

Cool image time! The Mars Reconnaissance Orbiter (MRO) image on the right, cropped and reduced in resolution to post here, shows the transition zone between the lower flat plain to the north and the higher but rougher region to the south. What makes it interesting is the north-south aligned mesas. These are yardangs, a geological feature that actually acts like a weather vane.

Yardangs are composed of sand grains that have clumped together and have become more resistant to erosion than their surrounding materials.

As the winds of Mars blow and erode away at the landscape, the more cohesive rock is left behind as a standing feature. (This Context Camera image shows several examples of yardangs that overlie the darker iron-rich material that makes up the lava plains in the southern portion of Elysium Planitia.) Resistant as they may be, the yardangs are not permanent, and will eventually be eroded away by the persistence of the Martian winds.

For scientists observing the Red Planet, yardangs serve as a useful indicator of regional prevailing wind direction. The sandy structures are slowly eroded down and carved into elongated shapes that point in the downwind direction, like giant weathervanes. In this instance, the yardangs are all aligned, pointing towards north-northwest. This shows that the winds in this area generally gust in that direction.

Crater splash

The wind comes from the southeast and blows to the northwest, and is slowly wearing down the southern rougher terrain. Why some of these yardangs are surrounded by dark material remains a mystery, as noted I noted in a previous post.

Meanwhile, the northern plain is not as boring as it seems. Only a short distance to the north is an unusual crater, cropped from the full image to show here on the right. To my eye, when this impact occurred it literally caused a splashlike feature of compressed and more resistant material. Over time, the prevailing wind has eroded away the surrounding less resistant regolith to better reveal that splash, leaving behind a mesa with a crater in its center.

Why the impact created this splash tells us something about the density and make-up of the plain. It suggests to me a surface that was once muddy and soft that over time has hardened like sandstone.


First science results from Juno

The Juno science team today released their first research results since the spacecraft entered orbit around Jupiter in July 2016.

“Although many of the observations have terrestrial analogs, it appears that different processes are at work creating the auroras,” said SwRI’s Dr. Phil Valek, JADE instrument lead. “With JADE we’ve observed plasmas upwelling from the upper atmosphere to help populate Jupiter’s magnetosphere. However, the energetic particles associated with Jovian auroras are very different from those that power the most intense auroral emissions at Earth.”

Also surprising, Jupiter’s signature bands disappear near its poles. JunoCam images show a chaotic scene of swirling storms up to the size of Mars towering above a bluish backdrop. Since the first observations of these belts and zones many decades ago, scientists have wondered how far beneath the gas giant’s swirling façade these features persist. Juno’s microwave sounding instrument reveals that topical weather phenomena extend deep below the cloudtops, to pressures of 100 bars, 100 times Earth’s air pressure at sea level.

“However, there’s a north-south asymmetry. The depths of the bands are distributed unequally,” Bolton said. “We’ve observed a narrow ammonia-rich plume at the equator. It resembles a deeper, wider version of the air currents that rise from Earth’s equator and generate the trade winds.”

Juno is mapping Jupiter’s gravitational and magnetic fields to better understand the planet’s interior structure and measure the mass of the core. Scientists think a dynamo — a rotating, convecting, electrically conducting fluid in a planet’s outer core — is the mechanism for generating the planetary magnetic fields. “Juno’s gravity field measurements differ significantly from what we expected, which has implications for the distribution of heavy elements in the interior, including the existence and mass of Jupiter’s core,” Bolton said. The magnitude of the observed magnetic field was 7.766 Gauss, significantly stronger than expected. But the real surprise was the dramatic spatial variation in the field, which was significantly higher than expected in some locations, and markedly lower in others. “We characterized the field to estimate the depth of the dynamo region, suggesting that it may occur in a molecular hydrogen layer above the pressure-induced transition to the metallic state.”

What I want to see is a depth map showing where Jupiter’s atmosphere ends and its solid core begins. I expect Juno will eventually be able to give us a first glimpse.


The storms of Jupiter’s south pole

storms on Jupiter

Cool image time! Even though Juno has been unable to gather any additional data since its first close approach of Jupiter in August because of technical problems, the science team has set up its website to allow the public to download the images produced so far, process those images, and then upload them to the site for the world to see.

The image to the right, reduced in resolution to show here, is one example of the many different processed images produced by interested members of the general public. It highlights the seemingly incoherent storms that are raging at Jupiter’s south pole.

close-up of storms

To the left is a cropped section of the full resolution image. It shows the complex transition zone between the darker polar regions and the brighter band that surrounds it. This chaotic atmospheric behavior is something that no climate scientist has ever seen before. It will take decades of research to untangle and even begin to understand what is happening.


More weird Pluto geology

fretted terrain

Cool image time! The New Horizons science team has released an image taken during the spacecraft’s fly-by of Pluto in July 2015 showing what they are calling “fretted terrain”.

The image above is a cropped reduced section of that image. It shows the strange transition zone between the higher elevation bright areas and the lower dark plains. As they note,

New Horizons scientists haven’t seen this type of terrain anywhere else on Pluto; in fact, it’s rare terrain across the solar system – the only other well-known example of such being Noctis Labyrinthus on Mars. The distinct interconnected valley network was likely formed by extensional fracturing of Pluto’s surface. The valleys separating the blocks may then have been widened by movement of nitrogen ice glaciers, or flowing liquids, or possibly by ice sublimation at the block margins.

In other words, they really don’t know what is going on.


Climate and Sun science bibliography

Below is a bibliography of all the research I have done on the subject of climate change, with a secondary focus on the question of the Sun’s influence on that climate. This bibliography covers a period from around 2002 until 2010, when I stopped adding to the list. The research continues, but I simply no longer amend this bibliography.

I publish it here both as a reference for my readers, and to also document the scope of my knowledge, should others ask why I have concluded that the field of climate science is very complex, that we really don’t know what is going on, and that anyone who says the science is settled has likely not done much research in the field. I don’t say that blindly. I base it on a careful review of the field, and the questions that good climate scientists are struggling with.

Note: The text that is in bold, including “?”, were my personal notes for items that needed to be more precisely written when the bibliography was finally published in a book. These notes also indicate where I can locate the pdfs some of these specific papers on my hard drive.


Balling, Robert C. Jr., 1992. The Heated Debate: Greenhouse Predictions Versus Climate Reality. San Francisco: Pacific Research Institute for Public Policy.

Bradley, Raymond S., 1999. Paleoclimatology: Reconstructing Climates of the Quarternary, second edition. San Diego: Academic Press.

Bradley, Raymond S., and Philip D. Jones, 1995. Climate Since A.D. 1500, Revised Edition. London: Routledge.

Broecker, W.S., 1992, revised 1995. The Glacial World According to Wally. Palisades, NY: Eldigo Press.

Burroughs, William James, 1992. Weather Cycles: Real or Imaginary? Cambridge, UK: Cambridge University Press.

Castagnoli, G. Cini, ed., 1988. Solar-Terrestrial Relationships and the Earth Environment in the last Millenna. Amsterdam: North-Holland Physics Publishing.

Cox, A.N., W.C. Livingston, M.S. Matthews, eds., 1991. Solar Interior and Atmosphere. Tucson: University of Arizona Press.

Dawson, Alastair G., 1992. Ice Age Earth: Late Quaternary geology and climate. London: Routledge.

Eddy, J.A., and H. Oeschger, 1993. Global Changes in the Perspective of the Past: report of the Dahlem Workshop, Berlin, December 8-13, 1991. Chichester, England: John Wiley & Sons, Ltd.

Fischer, Hubertus, Thomas Kumke, Gerrit Lohmann, Gtz Flser, Heinrich Miller, Hans von Storch, Jrg F.W. Negendank, eds., 2004. The Climate in Historical Times: towards a synthesis of Holocene proxy data and climate models. Berlin, Germany: Springer-Verlag.

Grove, Jean M., 1988. The Little Ice Age. London: Methuen & Co.

Harvey, Karen L., 1992. The Solar Cycle, proceedings of the National Solar Observatory/Sacramento Peak 12th summer workshop and of the fourth in series of solar cycle workshops held at NSO/Sacramento Peak October 15-18, 1991. San Francisco: Astronomical Society of the Pacific.

Herman, John R., and Richard A. Goldberg, 1978. Sun, Weather, and Climate. Washington, D.C.: NASA SP-426.

Houghton, John, 1997. Global Warming, the Complete Briefing, Second Edition. Cambridge, UK: Cambridge University Press.

__________~, 2004. Global Warming, the Complete Briefing, Third Edition. Cambridge, UK: Cambridge University Press.

Houghton, John, et al. 1990. Climate Change, the IPCC Scientific Assessment. Cambridge, UK: Cambridge University Press.

__________~, 1996. Climate Change 1995, the Science of Climate Change: Contribution of WGI to the Second Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge University Press.

__________~, 1997. An Introduction to Simple Climate Models used in the IPCC Second Assessmetn Report. IPPC

__________~, 2001. Climate Change 2001: The Scientific Basis: Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK: Cambridge University Press.

Hoyt, Douglas V., and Kenneth H. Schatten, 1997. The Role of the Sund in Climate Change. New York: Oxford University Press.

Imbrie, John, and Katherine Palmer Imbrie, 1979. Ice Ages: Solving the Mystery. Hillside, NJ: Enslow Publishers.

IPCC, 1995. Climate Change 1995, the Science of Climate Change, Summary for Policymakers and Technical Summary of the Working Group I Report. IPCC

Kippenhahn, Rudolf, 1994. Discovering the Secrets of the Sun. Chichester, UK: John Wiley & Sons.

Lang, Kenneth R., 1995. Sun, Earth, and Sky. Berlin, Germany: Springer-Verlag.

Leroux, Marcel, 2005. Global Warming: Myth or Reality? The Erring Ways of Climatology. Chichester, UK: Praxis Publishing Ltd.

National Research Council, 1994. Solar Influences on Global Change. Washington, D.C.: National Academy Press.

Pap, J.M., C. Frhlich, H.S. Hudson, S.K. Solanki, eds., 1994. The Sun as a Variable Star: Solar and Stellar Irradiance Variations, proceedings of IAU colloquium no. 143 held in Boulder, Colorado, USA, June 20-25, 1993. Cambridge, UK: Cambridge University Press.

Parkinson, Claire L., 2010. Coming Climate Crisis? Consider the Past, Beware the Big Fix. Plymouth, UK: Rowman & Littlefield Publishers, Inc.

Pepin, R.O., J.A. Eddy, and R.B. Merrill, eds., 1980. The Ancient Sun: Fossil record in the Earth, Moon, and Meteorites, proceedings of the conference on the ancient Sun, Boulder, Colorado, October 16-19, 1979. New York: Pergamon Press.

Rozelot, Jean Pierre, ed., 2003: The Sun’s Surface and Subsurface: Investigating Shape and Irradiance. Berlin: Springer-Verlag.

Schmelz, Joan T., and John C. Brown, eds., 1992: The Sun: a Laboratory for Astrophysics, proceedings of the NATO Advanced Study Institute, June 16-29, 1991, in Crieff, Scotland. The Netherlands: Kluwer Academic Publishers.

Schriver, C.J., and C. Zwaan, 200: Solar and Stellar Magnetic Activity. Cambridge, UK: Cambridge University Press.

Sonett, C.P., M.S. Giampapa, M.S. Matthews, 1991: The Sun in Time. Tucson: University of Arizona.

Thekaekara, Matthew P., 1965. Survey of the Literature of the Solar Constant and the Spectral Distributoin of Solar Radiant Flux. Washington, DC: NASA SP-74.

Warrick, R.A. E.M. Barrow and T.M.L. Wigley, 1993. Climate and sea level change: observations, projections, and implications. Cambridge, UK: Cambridge University Press.

Watson, Robert, et al~, 2001. Climate Change 2001: Synthesis Report. Cambridge, UK: Cambridge University Press.

Wefer, Gerold, Wolfgand H. Berger, Karl-Ernst Behre, and Eystein Jansen, eds., 2002: Climate Development and History of the North Atlantic Realm. Berlin: Springer-Verlag.

White, Oran R., 1977. The Solar Output and its Variation. Boulder, Colorado: Colorado Associated University Press.

Wilson, A., 2000. The Solar Cycle and Terrestrial Climate: proceedings of the 1st Solar and Space Weather Euroconference,
September 25-29, 2000, Instituto de Astrofsica de Canarias, Santa Cruz de Tenerife, Tenerife, Spain. Noordwijk, the Netherlands: ESA SP-463.

__________~, 2003. Solar Variability as an Input to the Earth’s Environment, proceedings of the International Solar Cycle Studies Symposium held at Tatransk Lomnica, Slovak Republic, June 23-28, 2003. Noordwijk, the Netherlands: ESA SP-535.

Wilson, Peter R., 1994: Solar and Stellar Activity Cycles. Cambridge, UK: Cambridge University Press.

Zerefos, Christos S., and Alkiviadis F. Bais, eds., 1997. Solar Ultraviolet Radiation: Modelling, Measurements, and Effects, proceedings held in Halkidiki, Greece, October 2-11, 1995. Berlin, Germany: Springer-Verlag.

Science Papers

Abramenko, Valentyna, Vasyl Yurchyshyn, Jon Linker, Zoran Mikic, Janet Luhmann, and Christina O. Lee, 2010?: Low-latitude coronal holes at the minimum of the 23rd solar cycle. ?[min23-24/1002.1685].

Abreu, J.A., J. Beer, F. Steinhilber, S.M. Tobias, and N.O. Weiss, 2008: For how long will the current grand maximum of solar activity persist? Geophysical Research Letters, 35, L20109, doi:10.1029/2008GL035442.

Altrock, Richard C., 2010?: The progress of solar cycle 24 at high latitudes. SOHO-23: Understanding a Peculiar Solar Minimum, ASP conference series, ?[min23-24/1002.2401].

Arge, C.N., E. Hildner, and V.J. Pizzo, 2002: Two solar cycles of nonincreasing magnetic flux. Journal of Geophyscial Research. 107, A10,1319, doi:10.1029/2001JA000503.

Asplund, Martin, Nicholas Grevesse, A. Jacques Sauval, and Pat Scott, 2009?: The chemical composition of the Sun. ?[solarcomp/0909.0948v1].

Balachandran,, David Rind, Patrick Lonergan, and Drew T. Shindell, 1999: Effects of solar cycle variability on the lower stratosphere and the troposphere. Journal of Geophysical Research, 104, D22, 27321-27,339.

Basri, Gibor, et al., 2010?: Photometric variability in Kepler target stars: The Sun among stars, a first look. ?[solarcomp/1001.0414].

Basu, Sarbani, Anne-Marie Broomhall, William J. Chaplin, Yvonne Elsworth, Stephen Fletcher, Roger New, 2010: Differences between the current solar minimum and earlier minima, SOHO-23: Understanding a Peculiar Solar Minimum, proceedings of the Northeast Harbor, Maine workshop, September 21-25, 2009, S. Cranmer, T. Hoeksema, and J.Kohl, eds., ?

Beer, Jrg and Ken McCracken, 2009: Evidence for solar forcing: Some selected aspects. Climate and Weather of the Sun-Earth System (CAWSES): Selected Papers from the 2007 Kyoto Symposium, T. Tsuda, R. Fujii, K. Shibata, and M.A. Geller, eds., 201-216.

Benevolenskaya, E.E., J.T. Hoeksema, A.G. Kosovichev, and P.H. Scherrer, ?: The interaction of new and old magnetic fluxes at the beginning of solar cycle 23. ?.

Berger, A., J.L. Mlice, M.F. Loutre, 2005: On the orgin of the 100-kyr cycles in the astronomical forcing. Paleoceanography, 20, PA4019, doi:10.1029/2005PA001173.

Bershadskii, A., 2009: Transitional dynamics of the solar convenction zone. Europhysics Letters, 85, 49002.

Bhatnagar, A., Kiran Jain, and S.C. Tripathy, 2002: Variation of solar irradiance and mode frequencies during Maunder Minimum. ?

Braun, Holger, Marcus Christi, Stefan Rahmstorf, Andrey Ganopolski, Augusto Mangini, Claudia Kubatzki, Kurt Roth, and Bernd Kromer, 2005: Possible solar orgin of the 1,470-year glacial climate cycle demonstrated in a coupled model. Nature 438, November 10, 2005, 161-166, doi:10.1038/nature04121.

Briffa, K.R., P.D. Jones, F.H. Schweingruber, and T.J. Osborn, 1998: Influence of volcanic eruptions on Northern Hemisphere summer temperature over the past 600 years. Nature 393, June 4, 1998, 450-454.

Burlaga, L.F., J.D. Richardson, and C. Wang, 2002: Speed fluctuations near 60 AU on scales from 1 day to 1 year: Observations and model. Journal of Geophysical Research, 107, A10,1328 doi:10.1029/2002JA009379.

Cahalan, Robert F., Guoyong Wen, Jerald W. Harder, and Peter Pilewskie, 2009: Temperature responses to spectral solar variability on decadal time scales, Geophysical Research Letters, 37, L07705, doi:10.1029/2009GL041898.

Calogovic, J., C. Albert, F. Arnold, J. Beer, L. Dosrgher, and E.O. Flueckiger, 2010: Sudden cosmic ray decreases: No change of global cloud cover. Geophysical Research Letters, 37, L03802, doi:10.1029/2009GL041327.

Coughlin, K. and K.K. Tung, 2004: Eleven-year solar cycle signal throughout the lower atmosphere. Journal of Geophysical Research, 109, D21105, doi:10.1029/2004JD004873.

Cranmer, S.R., 2004?: New insights into solar wind physics from SOHO. ?[solarfeatures/0409260].

Curdt, Werner and Hui Tian, 2010?: Hydrogen Lyman emission through the solar cycle. ?[min23-24/1002.3551].

D’Aleo, Joseph. 2007: Shining more light on the solar factor: a discussion of problems with the Royal Society paper by Lockwood and Frhich. Science and Public Policy Institute, available as of February 26, 2010 at

Damon, Paul, 2004: Pattern of Strange Errors Plagues Solar Activity and Terrestrial Climate Data. EOS, 85, 39, 9/28/2004, 370, 374.

Dere, K.P., A. Vourlidas, P. Subramanian, 2000: LASCO and EIT observations of coronal mass ejections. Proceedings of the YOHKOH 8th Anniversary International Symposium, “Explosive Phenomena in Solar and Space Plasma, December 6-8, 1999, Sagamihara, Japan.

del Toro Iniesta, J.C., and D. Orozco Surez, 2010: Size matters. ?Astron. Nachr./An, 1, 5?[solarfeatures/1002.3106].

Dikpati, Mausumi, Peter A. Gilman, and Rajaram P. Kane, 2010: Length of a minimum as predictor of next solar cycle’s strength, Geophysical Research Letters, 37, L06104, doi:10.1029/2009GL042280.

Didkovsky, Leonid V., Darrell L. Judge, Seth R. Wieman, 2009?: Minima of solar cycles 22/23 and 23/24 as seen in SOHO/CELIAS/SEM absolute solar EUV flux. ?[min23-24/0911.0870].

Douglass, David H. and B. David Clader, 2002: Climate sensitivity of the Earth to solar irradiance. Geophysical Research Letters, 29, 16, doi:10.1029/2002GL15345.

Erlykin, A.D., T. Sloan, and A.W. Wolfendale, 2010: Clouds, solar irradiance and mean surface temperature over the last century. Journal of Atmospheric and Solar-Terretrial Physics, 72, 425-434.

Feulner, Georg, and Stefan Rahmstorf, 2010: On the effect of a new grand minimum of solar activity on the future climate on Earth.Geophysical Research Letters, 37, L05707, doi:10.1029/2010GL042710.

Fiala, Alan D., David W. Dunham, and Sabatino Sofia, 1994: Variation of the solar diameter from solar eclipse observations, 1715-1991. Solar Physics, 152, 97-104.

Fleitmann, Dominik, Stephen J. Burns, Manfred Mudelsee, Ulrich Neff, Jan Kramers, Augusto Mangini, and Albert Matter, 2003: Holocene forcing of the Indian monsoon recorded in a stalagmite from southern Oman. Science, 300, June 13, 2003, 1737-1739.

Fligge, M. and S.K. Solanki, 2000: The solar spectral irradiance since 1700. Geophysical Research Letters, 27, 14, 2157-2160.

Foukal, P., C. Frhlich, H. Spruit, and T.M.L. Wigley, 2006: Variations in solar luminosity and their effect on the Earth’s climate. Nature, 443, September 14, 2006, 161-166, doi:10.1038/nature05072.

__________~, Gerald North, Tom Wigley, 2006: A stellar view on solar variations and climate. Science, 306, 68-69.

Friis-Christensen, E., and K. Lassen, 1991: Length of the solar cycle: an indicator of solar activity closely associated with climate. Science, New Series, 254, 5032 (November 1, 1991), 698-700.

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~__________~, 2009: Evidence of a long-term trend in total solar irradiance. Astronomy and Astrophysics, 501, L27-L30, doi:10.1051/0004-6361/2000912318.

Georgieva, Katya, and Boian Kirov, 2010?: Solar Dynamo and geomagnetic activity. [Dynamo/1003.2533]

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Gizon, Laurent, Aaron C. Birch, and Henk C. Spruit, 2010?: Local helioseismology: Three dimensional imaging of the solar interior. ?[solarfeatures/1001.0930].

__________~, et al., 2010?: Helioseismology of sunspots: A case study of NOAA region 9787. ?[solarfeatures/1002.2369].

Gleisner, Hans, and Peter Thejll, 2003: Patterns of tropospheric response to solar variability. Geophysical Research Letters, 30, 13,1711 doi:10.1029/2003GL017129.

Guinan, Edward F., and Scott G. Engle, 2009: The sun in time: Age, rotation, and magnetic activity of the Sun and solar-type stars and effects on hosted planets. The Ages of Stars, Proceedings IAU Symposium No. 258, E.E. Mamajek and D. Soderblom, eds.

Haigh, Joanna D., 2009: Mechanisms for solar influence on the Earth’s climate. Climate and Weather of the Sun-Earth System (CAWSES): Selected Papers from the 2007 Kyoto Symposium, T. Tsuda, R. Fujii, K. Shibata, and M.A. Geller, eds., 231-256.

Hall, Jeffrey C., and G.W. Lockwood, 2004: The chromospheric activity and variability of cycling and flat activity solar-analog stars. Astrophysical Journal, 614, 942-946, October 20, 2004.

__________~, 2009: The stars as a sun: Secular variations of cycling and non-cycling stars, a science white paper for the Astro 2010 Decadal Survey. available as 3/1/10 at

Harder, Jerald W., Juan M. Fontenla, Peter Pilewskie, Erik C. Richard, and Thomas N. Woods, 2009: Trends in solar spectral irradiance variability in the visible and infrared. Geophysical Research Letters, 36, L07801 doi:10.1029/2008GL036797.

Hathaway, David H., 2010: Does the current minimum validate (or invalidate) cycle prediction methods?, SOHO-23: Understanding a Peculiar Solar Minimum, proceedings of the Northeast Harbor, Maine workshop, September 21-25, 2009, S. Cranmer, T. Hoeksema, and J.Kohl, eds., ?

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Hudson, H.S. and Yan Li, 2010: Flare and CME properties and rates at sunspot minimum, SOHO-23: Understanding a Peculiar Solar Minimum, proceedings of the Northeast Harbor, Maine workshop, September 21-25, 2009, S. Cranmer, T. Hoeksema, and J.Kohl, eds., ?

Jain, Kiran, S.C. Tripathy, O. Burtseva, I. Gonzlez Hernndez, F. Hill, R. Howe, S. Kholikov, R. Komm, and J. Leibacher, 2010?: What solar oscillation tells us about the solar minimum. ?[mim23-24/1002.2411].

Javaraiah, J., 2009: Predicting the amplitude of a solar cycle using north-south asymmetry in the previous cycle: II. an improved prediction for solar cycle 24. Solar Physics ?

__________~, R.K. Ulrich, L. Bertello, J.E. Boyden, 2009?: Search for short-term periodicities in the Sun’s surface rotation: A revisit. Solar Physics ?[solarfeatures/0903.4031].

Judge, P.G., J. Burkepile, G. de Toma, 2010?: Historical eclipses and the recent solar minimum corona. ?[min23-24/1001.5278].

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