Tag: geology

Stardust found in meteorite older than Earth

9:12 am

Scientists studying what they think is grains of stardust in a meteorite the hit the Earth in 1969 have discovered the oldest material ever found on Earth, material that is actually older than the Earth itself.

The meteorite, dubbed the Murchison meteorite after the nearest city in Australia where it landed, has been a treasure trove of information for planetary scientists because so much of it was recovered right after impact.

About 30 years ago it was found that the rocks housed “presolar grains” – tiny grains of silicon carbide older than the Sun. But their exact age hadn’t been determined until now.

To figure that out, the researchers on the new study measured how long these presolar grains had been exposed to cosmic rays. These high-energy particles flit around space and can pass through solid matter, creating new elements inside the existing minerals as they interact with them. That means the scientists can measure the amount of these new elements in the grains to determine how long they were floating around in space – and, ultimately, how old they are.

In doing so, the team found that most of the grains were between 4.6 and 4.9 billion years old. The Sun itself is at the younger end of that range, at 4.6 billion years old, while the Earth didn’t form until 4.5 billion years ago.

But the oldest of the grains were dated to more than 5.5 billion years, making them the oldest known material on Earth. The team says that the history of these grains could be traced back even further, to the stars that birthed them some 7 billion years ago. According to the researchers, this finding suggests that our galaxy went through a period of intense star formation around that time.

Obviously there are uncertainties with this result, though their age estimates are quite reasonable and largely robust.

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Curiosity climbs a hill

5:07 pm

Overview map of Curiosity's journey through sol 2643

[For the overall context of Curiosity’s travels, see my March 2016 post, Pinpointing Curiosity’s location in Gale Crater.

For the updates in 2018 go here. For a full list of updates before February 8, 2018, go here.]

Since my last Curiosity update on November 6, 2019, the science team has sent the rover climbing up what they call Western Butte, the butte directly to the west of Central Butte and part of the slope/escarpment that separates the clay unit from the Greenheugh Piedmont and the sulfate unit above that.

The overview map to the right gives a sense of the journey. The thick yellow line indicates its route since it climbed up from the Murray Formation onto Vera Rubin Ridge in 2017. The thick red line indicates their planned route, which they have only vaguely been following since their arrival in the clay unit.

Below the fold are two panoramas that I created from a sequence of images taken by Curiosity’s left navigation camera from the high point on Western Butte, the first looking north across the crater floor to the Gale Crater rim approximately 30 miles away and indicated by the thin yellow lines on the overview map. The second looks south, up hill towards Mount Sharp, and is indicate by the thin red lines.
» Read more

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Pedestal craters in the Martian northern lowlands?

1:59 pm

Pedestal craters on Mars?
Click for full image.

Cool image time! The photo on the right, cropped and reduced to post here, shows a cluster of really strange mesas, craters, and pits, located in Utopia Planitia, the largest and deepest plain of Mars’ northern lowlands where an intermittent ocean might have once existed.

The image was taken on October 26, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) as part of its regular image-taking program. In this case it was dubbed a “terrain sample” image, meaning that it was not specifically requested by any researcher, but was taken because they need to use the camera regularly to maintain its temperature, and thus sometime produce images over previously untouched areas, not knowing what they will find, as part of that maintenance schedule.

In this case the terrain sampled is especially intriguing. Are the upraised depressions what are called pedestal craters, created when the impact landed on what was once an icy plain, which subsequently sublimated away to leave the crater sitting high above the surrounding flats? Maybe, but this location is at 23 degrees north latitude, and research has generally found these pedestal craters at latitudes higher than 30 degrees.

Moreover, that many of these upraised depressions are not circular suggests that their formation was not impact related.

Other mysteries: Why are all the ridgelines bright? What caused the parallel white streaks to the east and west of some mesas? And if these are impact craters, why are some distorted?

If this region was once the seabed of an intermittent ocean, this fact might explain the features. Then again, it is more likely that this lowland area was once covered in ice in the far past, when the planet’s tilt was greater and the lower latitudes were actually colder than the polar regions, and thus allowed ice to build up in those lower latitudes. We might therefore be seeing the end result of an erosion/sublimation process as that ice disappeared when Mars’ inclination shifted.

Lots of questions, and no answers.

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Yutu-2 completes 13th lunar day

9:02 am

China’s Yutu-2 lunar rover and its lander Chang’e-4 have completed their thirteenth lunar day on the far side of the Moon and have been placed in sleep mode.

During the twelve lunar day the rover traveled about 12 meters, or about 40 feet.

The rover has found materials from deep inside the moon that could help unravel the mystery of the lunar mantle’s composition and the formation and evolution of the moon and the earth. Using data obtained by the visible and near-infrared spectrometer installed on Yutu-2, Chinese scientists found that the lunar soil in the landing area of the Chang’e-4 probe contains olivine and pyroxene which came from the lunar mantle deep inside the moon.

Due to the complicated geological environment and the rugged and heavily cratered terrain on the far side of the moon, the rover drives slowly but steadily and is expected to continue traveling on the moon and make more scientific discoveries.

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Darkened craters on Mars

1:13 pm

Darkened craters on Elysium Planitia
Click for full image.

It’s time for the first cool image of 2020! The photo to the right, cropped and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 10, 2019. It shows a handful of darkened craters on the vast volcanic Elysium Planitia plain between the giant volcanoes Olympus Mons to the east and Elysium Mons to the north.

My first thought was that these dark craters were recent crater impacts, possibly a set of secondary impacts from a larger nearby impact. However, in looking at the archive of MRO’s high resolution camera at this location (Latitude 5.925° norther; Longitude 164.965°) I found that almost no high resolution images have been taken in this region, as shown by the overview map below to the right.
» Read more

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Giant scallops on Mars

2:48 pm

Scallops on Mars
Click for full image.

It’s a slow news week, with the too much partying only real space news today the expected third launch of China’s Long March 5 rocket (supposedly scheduled for this morning but so far no word). (To my gentle reader: For some reason I have been losing a day during this whole week, always thinking that Christmas was on Thursday and that today was Friday. Thus my error in thinking the Long March 5 flight was today. It is tomorrow morning. Forgive me for my absent-mindedness.) So let’s look at a cool image!

The photo on the right, cropped and reduced to post here, was taken my the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 8, 2019. Entitled “Scalloped Depressions in Utopia Planitia,” it shows a strangely eroded surface in the northern lowlands of Mars, where an intermittent ocean might have once existed.

The location of these scallops is shown to the right.

Location of scallops in Utopia Planitia

I have taken the same overview map used from two recent cool image posts, showing how these scallops relate in location to the strange crater in Utopia Planitia as well as the glacial-surrounded mesa in Protonilus Mensae.

In caves, scallops like this form from water or wind flow, but when they do, they are all oriented the same way. Here the scallops are at different orientations, terracing down from the center of the image. In this case it appears that scientists believe [pdf] the formation process is related to the sublimation of underground ice at this location.

According to [one hypothesis] scallop formation should be ongoing at the present time. Sublimation of interstitial ice could induce a collapse of material, initially as a small pit, then growing southward because of greater solar heating on the southern side. Nearby scallops would coalesce together as can be seen to have occurred.

What is most cool is that the geologists think the process that forms these scallops is related to the same processes that cause the formation of the swiss cheese landforms in the south polar regions.

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Crater in the Martian northern lowlands

11:32 am

Crater in Utopia Planitia
Click for original full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 26, 2019. It shows a crater in the western edge of Utopia Planitia, the largest and deepest region of the Martian northern lowlands where it is theorized that an intermittent ocean might have once existed.

My first uneducated guess at looking at this image is that the impact occurred in some sort of wet slushy mud or ice, which then melted and filled the crater interior, ponding in the crater’s center as it froze.

A more educated guess, based on what I have learned in the past year, is not much different. The crater is located at 40 degrees north latitude and therefore sits in the middle of the mid-latitude band where scientists think there are a lot of buried inactive glaciers.

Overview map

The map to the right, revised from my December 20, 2019 post about glaciers flowing off the slopes of a mid-latitude mesa, illustrates this even more clearly.

This crater, indicated by the white cross, sits at approximately the same latitude as that mesa and its glaciers in Protonilus Mensae. It also sits at in an area where accumulated data from several spacecraft have mapped a lot of water ice, close to the surface.

Thus, it is reasonable to suppose that the impact that made this crater pushed into that ice-table, melting the water which subsequently froze and then subsided downward into the ground to form the crater’s central ponded features.

Or to put it as I did initially, the impact smashed into some wet slushy mud/ice, melting it so that it filled the crater interior to then freeze as we see it.

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A deep dive into Valles Marineris

2:56 pm

Dunes on the floor of Valles Marineris
Click for full image.

The vastness of Mars is sometimes hard to fathom. While the planet is much smaller than Earth, its entire global surface is approximately the same as the Earth’s land area. This is a lot of territory. It took humanity many tens of thousands of centuries to expand outward to settle all of it. It took even longer before humanity was successfully able to map all of the Earth so that its entire surface was known to all humans, a task that was only completed a handful of centuries ago.

While we now have the technology to quickly map the entire globe of a planet like Mars, the devil is always in the details. At this time the resolution of our global maps give us only a glimpse of the Martian surface.

The image to the right, reduced and cropped to post here, is a good example. Taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 30, 2019, it shows a set of large dunes on the northern floor of a side canyon on Mars that is part of Coprates Chasma, a canyon that forms only a small part of the vast Valles Marineris canyon system east of the giant volcanoes of the Tharsis Bulge.

The sand of these dunes is mostly volcanic material, dark basalt that was deposited as lava from those giant volcanoes, then later ground down in landslides and erosion to be recycled as sand that formed dunes trapped within the canyon bottom. The dunes themselves are slowly moving eastward, driven mostly by the predominate west-to-east winds that blow down this side canyon of Coprates Chasma. The motion is very slow, so slow that even though the image title is “Coprates Chasma Dune Changes”, I was unable to spot any changes when I compared this 2019 image with a photo taken in June 2019.

To find out what had changed, I contacted Matt Chojnacki of the Lunar and Planetary Laboratory at the University of Arizona, who has been studying the nature of the sand dunes in Valles Marineris. After making a quick preliminary blink test using more sophisticate tools than I have available, he found “minor advancements. The rocks move a bit too in places.” Without a full analysis he also added, “I can tell some dune crests have moved to the east.”

The research by Chojnacki and others has found that the dunes within Valles Marineris are in many ways different than dunes found elsewhere in the mid-latitudes on Mars, suggesting that being trapped within this giant canyon has produced some specific regional features. They tend to be darker, the canyon contains several sand dune seas, called ergs (only seen elsewhere on Mars in the polar regions), and the dunes tend to be more hardened, so that they change relatively little when compared to similar dunes elsewhere on Mars.

These particular dunes in Coprates Chasma however are not hardened, since if so they would have been covered by the landslides and material that comes down from the canyon’s nearby northern slopes. Instead, they move, but appear to move far slower than similar dunes elsewhere on Mars.

To me, this image provides a good vehicle for getting a sense of the size of Valles Marineris. Coprates Chasma itself only one of about a dozen named sections of the entire Valles Marineris canyon system, and this particular image shows only the floor of a side canyon of Coprates. The map below gives an overview of the entire system.
» Read more

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Megadunes in the giant canyon of Mars’ north polar icecap

1:02 pm

Martian megadunes at the beginning of summer
Click for full image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken by the high resolution camera of Mars Reconnaissance Orbiter (MRO) on September 15, 2019, right at the beginning of summer at the north polar icecap of Mars.

Without a larger context it is very difficult to figure out what this image shows. The image title, “Seasonal Changes of Chasma Boreale Megadunes,” gives us some basic clues. The streaks of black and dark grey are giant dunes, with this image showing their trailing edge. The darkest streaks are likely places where the thin winter mantle of dry ice has begun to sublimate away with the coming of spring, exposing the darker sand dunes below. The surrounding flat white areas are either the permanent water ice of the icecap or the surface of the lowland northern plains that surround that icecap.

The montage below shows a series of monitoring photos, beginning in 2018 during the last Martian summer and continuing through the start and middle of the spring and ending with the photo above. It shows the seasonal evolution of that upper carbon dioxide dry ice mantle, which reveals the darker dunes below as that dry ice mantle sublimates away.
» Read more

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A crack in the Martian crust

3:39 pm

Crack in the Martian crust
Click for full image.

Cerberus Fossae

The photograph to the right, reduced and cropped to post here, was imaged on October 20, 2019 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a spectacular thousand-foot-deep canyon in the region of Cerberus Fossae, an area of Mars crossed by numerous deep east-west fissures and depressions.

Hidden in the small white box on the eastern end of that canyon are Martian geological features, small and at first glance not that interesting, that are of great significance and the focus of intense research.

The map to the right shows an overview of the region. The yellow cross shows the location of this particular crack.

In my previous post about Cerberus Fossae, I had incorrectly assumed that these cracks and similar lines of pits or depressions were caused by the sinking of surface material into underground lava tubes. While this is possible in some cases, it is not the main cause of these cracks. Instead, they were formed due to the pressure from below caused by the rise of the surrounding giant volcanoes, Elysium Mons to the north and Olympus Mons to the east. That pressure stretched the crust until it cracked in numerous places. In Cerberus Fossae this produced a series of parallel east-west fissures, some more than seven hundred miles long.

The young age of Cerberus Fossae is dramatically illustrated by the wider mosaic below, showing the entire crack.
» Read more

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Martian “What the heck?” formations

2:41 pm

What the heck caused these?
Click for full image.

Cool image time! In digging through the new images that come down from the high resolution camera on Mars Reconnaissance Orbiter (MRO), my reaction sometimes is “What the heck caused that?”

That was my reaction when I looked at the image to the right, cropped to post here.

The full image, taken on October 6, 2019, shows the floor of one of the many north-south fissures found in the volcanic Tharsis Bulge west of Valles Marineris and east of Olympus Mons. The fissures are caused when the crust is pushed upward by volcanic pressure, causing the surface to crack.

In this case the mystery is that patch of east-west ridges at the bottom of this somewhat wide fissure. While they might be dunes, they do not resemble dunes, as they have a rigid and somewhat sharp appearance. More puzzling is their somewhat abrupt appearance and disappearance. Except for its northern end, the edges of the patch are so sharply defined. If these were dunes you’d think they’d fade away more gradually.

Could the ridges be a more resistant subsurface feature slowly being revealed as surface material erodes away? Sure, but their orientation is completely opposite to the north-south fissures that dominate this region. One would expect deeper features to reflect that same general orientation. These ridges do not.

This image was dubbed a “Terrain Sample,” which means it was taken not because of any specific research goal, but because the scientists who run MRO’s high resolution camera had a gap in their schedule and needed to take a picture to maintain the camera’s proper temperature. In such cases they often take somewhat random images, not knowing what they will find. In this case they struck geological gold, a mystery that some postdoc student could spend a lot of time analyzing.

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Mars Express confirms ancient glaciers in northern Martian mid-latitudes

9:46 pm

Perspective view of Deuteronilus Mensae
Click for full image.

The European Space Agency’s orbiter Mars Express has confirmed the presence of large fractured ice sheets suggestive of buried and ancient glaciers. These ice sheets are within one region on Mars located in the mid-latitudes where many such glacial features have been found. They are also in the transition zone between the northern lowlands and the southern highlands.

This landscape shows clear and widespread signs of significant, lasting erosion. As is common with fretted terrain, it contains a mix of cliffs, canyons, scarps, steep-sided and flat-topped mounds (mesa), furrows, fractured ridges and more, a selection of which can be seen dotted across the frame.

These features were created as flowing material dissected the area, cutting through the existing landscape and carving out a web of winding channels. In the case of Deuteronilus Mensae, flowing ice is the most likely culprit. Scientists believe that this terrain has experienced extensive past glacial activity across numerous martian epochs.

It is thought that glaciers slowly but surely ate away at the plains and plateaus that once covered this region, leaving only a scattering of steep, flat, isolated mounds of rock in their wake.

Smooth deposits cover the floor itself, some marked with flow patterns from material slowly moving downhill – a mix of ice and accumulated debris that came together to form and feed viscous, moving flows of mass somewhat akin to a landslide or mudflow here on Earth.

Studies of this region by NASA’s Mars Reconnaissance Orbiter [MRO] have shown that most of the features seen here do indeed contain high levels of water ice. Estimates place the ice content of some glacial features in the region at up to 90%. This suggests that, rather than hosting individual or occasional icy pockets and glaciers, Deuteronilus Mensae may actually represent the remnants of an old regional ice sheet. This ice sheet may once have covered the entire area, lying atop the plateaus and plains. As the martian climate changed this ice began to shift around and disappear, slowly revealing the rock beneath.

Overall, the data coming from both Mars Express and MRO increasingly suggests that there is a lot of buried glacial ice in the mid-latitudes. Mars might be a desert, but it is increasingly beginning to look like much of the planet is a desert like Antarctica, not the Sahara.

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