Tag: geology

Frozen lava flows around Martian hills

5:06 pm

Martian lava flowing around hills
Click for full image.

Cool image time! The photo to the right, rotated, cropped, reduced, and enhanced to post here, was taken on August 24, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the westernmost edge of the Athabasca flood lava plain, thought to be the youngest lava flow on Mars, having covered the area of Great Britain in a matter of weeks 600 million years ago.

This image was a captioned feature yesterday by the MRO science team. As they note:

Although you can’t sail a boat on a sea of lava, hills and craters that stick up higher than the lava flow act like barriers. When a boat is driven through the water, there is a bow wave at the front of the boat, and a wake that trails off behind that indicates which way the boat is moving. In a lava flow, when a hill sticks up, the lava piles up on the upstream side (just like a bow wave) and can leave a wake on the downstream side, so we can tell which way the lava was moving against the stationary hill.

As you can see, every hill has a pile of lava on its northeast slopes, and a wake to its southeast. As the main vent of the Athabasca eruption is to the northeast, about 500 miles away (as shown on the overview map below), the flow direction suggested by the wakes fit the general geography.
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Inverted river on Mars

1:52 pm

Inverted river on Mars

Cool image time! The photo to the right, rotated, cropped, reduced, and enhanced to post here, was taken on May 30, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as a “inverted fluvial system”.

Such features are not unusual on Mars. The theory explaining their formation is that this was once a channel where either water or ice flowed, packing the streambed down so that it was more dense than the surrounding terrain. After the flowing material disappeared, the less dense surrounding terrain eroded away, leaving the channel as a meandering ridge.

The location of this inverted channel, as shown in the overview map below, lends some weight to the flowing material being water or ice.
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Perseverance spots Phobos

10:57 am

Phobos, as seen by Perseverance on Mars
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Cool image time! The photo to the right, cropped to post here, was taken on January 12, 2022 by one of the high resolution cameras on the Mars rover Perseverance, and shows the Martian moon Phobos.

As noted in an update today by Claire Newman, one of the members of the science team,

This provides a measurement, using visible light, of the amount of dust in the nighttime atmosphere, which can be compared to similar measurements made by looking at the sun during the daytime, and to nighttime measurements of dust abundance made in the infrared by MEDA [another Perseverance instrument].

There have been three attempts to land on Phobos, all by the Russians, all of which failed. At present a Japanese mission to Phobos, dubbed Mars Moons eXploration or MMX, is scheduled to launch in 2024. This is a planned sample return mission, and will also include a rover.

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Changing slope streaks on Mars

3:08 pm

Overview map

Changing slope streaks on Mars
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on July 20, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists have labeled a “Splitting Slope Streak” on a mound/hill near the equator and located almost midpoint between the giant volcano Olympus Mons about 2,000 miles to the east and the almost as big volcano Elysium Mons about 2,500 miles to the west. The white cross on the overview map above marks this location, north of the Medusae Fossae volcanic ash deposit.

The slope streak in question is the biggest and darkest at about 7 o’clock. Slope streaks are a feature unique to Mars that remain as yet unexplained. They are not ordinary avalanches, despite their appearance. They seem to have no effect on the topography, and thus are more a stain on the surface. Moreover, some are bright, some dark, and all happen randomly and fade with time. Some think they may be brine-related, while others link them to dust. No theory explains them completely.

What makes this slope streak interesting is that it is relatively new. Compare it with the picture taken in 2016 below.
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An icy hollow on Mars

2:07 pm

A icy hollow on Mars
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Cool image time! The photo to the right, cropped, reduced, and enhanced to post here, was taken on August 20, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a somewhat typical example of the many ice scarps that scientists have identified in MRO pictures.

Though this is not a hard fast rule, most of the ice scarps so far found tend to have the steep cliff on the pole-facing side, with the scarp very slowly retreating towards the equator. In today’s example, the scarp where an ice layer in the cliff wall has been identified is indicated by the white arrow, though three sides of the hollow, on the east, north, and west sides, could all also have exposed ice.

Nor is that the only likely ice at this location at 56 degrees south latitude. The stippled plain surrounding the hollow clearly looks like an eroded ice layer, likely covered with a thin protective coat of dust to protect if from quickly sublimating away. The dark streaks across this surface are likely dust devil tracks.

As documented by the global map below, Mars is like Antarctica, a desert with water ice everywhere.
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DART’s impact shortened Dimorphus’s orbit around Didymos by 32 minutes

5:51 pm

LICIACube Explorer image of DART impact
LICIACube Explorer image just after the DART
impact. Dimorphus is the blob near the top.

After two weeks of analyzing the orbit of Dimorphus around its parent asteroid Didymos, astronomers have determined that the impact of DART on Dimorphus shortened its orbit by 32 minutes.

Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit its larger parent asteroid, Didymos. Since DART’s intentional collision with Dimorphos on Sept. 26, astronomers have been using telescopes on Earth to measure how much that time has changed. Now, the investigation team has confirmed the spacecraft’s impact altered Dimorphos’ orbit around Didymos by 32 minutes, shortening the 11 hour and 55-minute orbit to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes.

Before its encounter, NASA had defined a minimum successful orbit period change of Dimorphos as change of 73 seconds or more. This early data show DART surpassed this minimum benchmark by more than 25 times.

It also appears the ejecta from the impact — much greater than expected — helped propel Dimorphus, a result that I think was also not expected.

Researchers are now shifting to studying the debris and asteroid itself, to better understand what happened as well as the nature of Dimorphus itself. This will also include a European probe dubbed Hera that will launch in 2024 an dvisit both asteroids in 2026.

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Volcano on the Moon

10:08 am

Wide shot of lunar volcano

Close-up of lunar volcano
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Cool image time! The Lunar Reconnaissance Orbiter (LRO) science team today released the oblique image above and in close-up to the right, showing what they call a “silicic volcano.” From the release:

The Mairan T dome is a large silicic volcanic structure with a pronounced summit depression. Remote sensing indicates that the composition of the volcanic material (lava) making up the dome is enriched in silica (SiO2). This rock type would be classified as either rhyolite or dacite on Earth, and the composition starkly contrasts with the dark, iron-rich mare basalts that embay the Mairan T dome. Most of the volcanism on the Moon is basaltic or iron-rich. Still, silicic volcanism also occurred on the Moon. Indeed, bits and pieces of similar materials were found in the Apollo samples; however, all are small fragments delivered to the Apollo sites as material ejected from distant impact events.

One of the great questions for lunar science is how the silicic materials formed. On Earth, specific tectonic settings and higher water contents in the rocks favor the formation of such lavas; however, the Moon lacks plate tectonics and water-rich sediments. NASA is planning a Commercial Lunar Payload Services (CLPS) lander mission to another, larger silicic volcano, one of the Gruithuisen domes, to address this question.

The scientists also note that this volcano formed first, and then was partly covered by the dark flood lava that surrounds it.

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InSight’s power levels rise very slightly

9:55 pm

InSight's power level through October 8, 2022

In a status report issued today, the science team for the InSight lander on Mars noted a slight increase in the amount of power produced daily by its solar panels. The graph to the right indicates that increase.

On October 8, 2022, InSight was generating an average of 300 watt-hours of energy per Martian day, or sol – an increase after a sharp decline last week from 430 watt-hours per sol to a low of 275 watt-hours per sol.

It appears that the atmosphere has begun to clear from the very large dust storm that occurred more than two thousand miles away. Despite that distance, the storm apparently reduced the available light above InSight significantly, and could take months to clear.

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Icebergs of Martian lava

1:52 pm

Icebergs of Martian lava
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Cool image time! The photo to the right, cropped, reduced, and enhanced to post here, was taken on July 24, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The scientists label this “platy-ridged lava” but to my eye this more resembles lava ice bergs trapped within a now frozen lava stream flowing I think from the northeast to the southwest.

My guess that the flow follows that direction is based on two bits of data. First, the shape of the lava ice flows suggests vaguely a flow to the southwest. The wiggling black ridges inside the streams suggest that these flows occurred in two parts, a stronger wide flow that narrowed as the lava on the edges hardened. When the edges solidified the interior flow scraped against it, forming the wiggling ridges.

Second, the location of this image, as shown on the overview map below, strongly suggests the lava streams flowed to the southwest.
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InSight shut down temporarily because of lack of power

10:14 am

InSight's power levels over recent time

Because a dust storm has caused a further decline in the power being generated by InSight’s solar panels, the science team has decided to put the lander into safe mode for the next two weeks in the hope that the air will then clear, allowing its power levels to rise.

The graph to the right shows that drop. From the press release:

By Monday, Oct. 3, the storm had grown large enough and was lofting so much dust that the thickness of the dusty haze in the Martian atmosphere had increased by nearly 40% around InSight. With less sunlight reaching the lander’s panels, its energy fell from 425 watt-hours per Martian day, or sol, to just 275 watt-hours per sol.

InSight’s seismometer has been operating for about 24 hours every other Martian day. But the drop in solar power does not leave enough energy to completely charge the batteries every sol. At the current rate of discharge, the lander would be able to operate only for several weeks. So to conserve energy, the mission will turn off InSight’s seismometer for the next two weeks.

The real problem however is the dust covering the solar panels. If that dust gets thicker due to this storm, the lander will not recover when they power it up in two weeks. It will still generate electricity at this low number, making future operations likely impossible.

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Thick flow exiting dramatic canyon on Mars

1:22 pm

Thick flow into Mamers Valles on Mars
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on July 24, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what the scientists label as a “viscous flow” that has apparently carved the wide curving canyon as it slowly flows into open country to the south.

I would estimate the height of that canyon wall to be around 3,000 feet, though this is a very rough guess. I also image a trail switchbacking up the nose of that canyon wall would make for a truly stupendous hiking experience.

The flow filling the canyon floor appears very glacial, which is not surprising as this canyon is at 37 degrees north latitude, in the mid-latitude band where many glacial features are found. The overview map below provides some more detailed context.
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Martian crater and mesa sculpted by ancient flow

1:14 pm

Martian crater and mesa sculpted by ancient flow
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Cool image time! The picture to the right, rotated, cropped, and reduced to post here, was taken on June 15, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a crater whose ejecta has been sculpted to the east into a teardrop-shaped mesa by some ancient flow, coming from the west.

The crater itself is located in one of several outflow canyons draining out from the volcanic Tharsis Bulge into the northern lowland plain of Chryse Planitia, the biggest of which is Valles Marineris. This particular canyon is one of the smaller and is dubbed Ravi Vallis.

The overview map below illustrates why many scientists think the flow that shaped this mesa came from a catastrophic flood of liquid water, billions of years ago.
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Another “What the heck?” formation on Mars

2:32 pm

Another
Click for full image.

Cool image time! The photo to the right, cropped, reduced, and enhanced to post here, was taken on May 28, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), and shows what the scientists label “unique terrain.”

I have increased the contrast to bring out the details. It appears that we have a flat plain of criss-crossing ridges that in large areas have somehow gotten flattened across their top. Imagine someone laying plaster on a wall and using a scraper tool to smooth the surface, but only partially. In this case on Mars, our imaginary worker only smoothed the surface a little, and only in some areas. To try to come up with a geological process however to explain this seems daunting.

And what created the criss-crossing ridges? The overview map provides only a little help in answering these questions.
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Two days after DART’s impact of Dimorphus, ejected dust extends like a comet tail out more than 6,000 miles

12:23 pm

Dust tail from Dimorphus two days after DART impact
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Using a telescope in Chile, astronomers photographed the ejecta two days after the impact of DART into the 525-foot-wide asteroid Dimorphus, and detected a tail of dust extending out more than 6,000 miles.

The picture to the right, cropped and reduced to post here, shows that tail.

In this new image, the dust trail — the ejecta that has been pushed away by the Sun’s radiation pressure, not unlike the tail of a comet — can be seen stretching from the center to the right-hand edge of the field of view. … At Didymos’s distance from Earth at the time of the observation, that would equate to at least 10,000 kilometers (6000 miles) from the point of impact.

Didymos is the larger parent asteroid that Dimorphus orbits.

It is still too soon to get the numbers on how Dimorphus’s path in space was changed by that impact. In fact, we still really don’t have a clear idea what is left of Dimophus itself. The ejecta cloud needs to clear somewhat to see what’s hidden inside it.

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Europa in true color

9:37 am

Europa in true color
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The photo to the right, cropped and reduced to post here, was taken on September 29, 2022 by the Jupiter orbiter Juno during its close fly-by of Europa. Citizen scientist Bjorn Jonsson has processed it to bring out the details. From his caption:

This is an approximately true color/contrast, reprocessed version of Europa image PJ45_1. It is more carefully processed than the version I posted very shortly after the raw image data was released. The color should be fairly close to Europa’s real color and probably slightly more accurate than the color of the earlier version I posted. North is up.

The Sun is coming from the right, so those are craters in the upper left, close to the shadowed limb of the planet. The red color has been known for decades, and appears in many cases to be seepage coming up from the many meandering ridges that criss-cross the planet’s surface. Their chemistry/make-up is not fully known at this time.

Juno came within 219 miles of Europa, the closest any spacecraft has come since the Galileo orbiter circled Jupiter in the 1990s. I was expecting close-up images of the surface, from that close distance, but have not yet seen any. Instead, most of the images released and processed by citizen scientists have been global images from farther away. Thus, at this moment it does not appear Juno took pictures at this closest distance.

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Tiny cobbles on Mars

9:16 am

Tiny cobbles on Mars

Our second cool image takes us from grand galaxies, one of the universe’s largest coherent objects, to tiny cobbles on Mars. The picture to the right, taken by one of Perseverance’s close-up cameras on September 29, 2022, covers an area less than an inch across, making the largest rounded pebbles in this image only a few millimeters in size.

The rover presently sits on the floor of Jezero Crater, at the base of the delta that flowed into that crater eons ago. The data suggests that delta was created by flowing water entering a lake that filled the crater.

Did flowing water create these cobbles? These pebbles all have the look of the rounded cobble one finds either in river beds, or in glacial moraines. In both cases, the flow of the water or ice rolls the rocks along until they become rounded.

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Lunar mountains and wrinkle ridges

12:13 pm

Montes Recti on the Moon

Cool image time! The photo above, taken by Lunar Reconnaissance Orbiter (LRO), was released today by the orbiter’s science team, and provides us an oblique look at the mountains dubbed Montes Recti (lower right) and the wrinkle ridges near them (lower left). The highest point in this mountain range is about 5,900 feet high.

The image looks west across the northern part of the mare region dubbed Mare Imbrium, the dark area on the Moon’s visible hemisphere near its top. In the distance can be the mountains that form part of mare’s rim. The rounded peak in the top right is Promontorium Laplace (about 8,530 feet high). It is named this because it projects out (a promontory) into the mare a considerable distance from the rim. The crater at top center is Laplace D. As for the wrinkle ridges, the scientists describe them like so:

Tectonic landforms are those formed by forces that act to either contract or pull apart crustal materials. These forces develop faults or breaks in the crustal materials, and movement or slip along the faults form either positive or negative relief landforms. On the Moon, positive relief contractional landforms are the most common. The most significant contractional landforms on the Moon are wrinkle ridges, found exclusively in the dark mare basalts.

Essentially, something caused the ground to contract, which caused it to break at these ridges and be forced upward.

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Chang’e-5 samples suggest lunar meteorite impacts took place the same time as big Chicxulub impact

10:23 am

In analyzing lunar samples brought back by China’s Chang’e-5 Moon lander, Australian scientists have found evidence of lunar meteorite impacts that apparently took place the same time as big Chicxulub impact in the Yucatan 66 million years ago, thought by many scientists to have caused the extinction of the dinosaurs.

Their findings suggest that the frequency of meteorite impacts on the Moon may have been mirrored on Earth, and that major impact events on Earth were not stand-alone events and instead were accompanies by a series of smaller impacts. The study has been published in Science Advances.

“We combined a wide range of microscopic analytical techniques, numerical modelling, and geological surveys to determine how these microscopic glass beads from the Moon were formed and when,” says lead author Professor Alexander Nemchin, from the Space Science and Technology Centre (SSTC) in the School of Earth and Planetary Sciences at Curtin University in Perth.

The data suggests two possibilities, neither of which is confirmed. First, the impacts could have occurred because a cluster of large objects hit both Earth and the Moon at the same time. Second, the impacts on the Moon could have been caused by objects thrown up from the Earth when the bigger impact occurred at Chicxulub.

Either way, the data suggests a greater and more complex interaction between events on the Earth and events on the Moon.

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More glaciers in Mars’ glacier country

2:24 pm

Overview map

glacial layering in Clasia Vallis
Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on June 18, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows what appear to be layered glacial features on the floor of what at first glance appears to be a crater.

It is not a crater however. The depression in the lower right of this image is the rim and floor of a 77-mile-long meandering canyon on Mars dubbed Clasia Vallis. The red cross in the overview map above marks its location, at 34 degrees north latitude. This channel drains downward from the southern cratered highlands into the 2,000-mile-long mid-latitude strip of mensae terrain that I dub glacier country because almost every hi-res image from this region shows glacial features.

Below is a wider view of Clasia Vallis, taken by the context camera on MRO on March 19, 2014.
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Zig-zag ridges on Mars

2:26 pm

Zig-zag ridges on Mars
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Cool image time! The photo to the right, cropped and reduced to post here, was taken on April 9, 2022v by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a series of parallel zig-zag ridges in a flat, knobby terrain.

I don’t presume to explain this at all. According to one research paper,

This interplana region consists of extensive networks of ridges—the eponymous Aeolis Dorsa—and is interpreted as having formed by topographic inversion of fluvial and alluvial deposits.

Why these ridges zig-zag however does not seem to fit into either a fluvial or alluvial explanation, both of which involve the flow of water. The quote implies these could be inverted stream channels (where the compacted streambed becomes a ridge when the surrounding terrain erodes away), but once again, the distinct zig-zag pattern seems wrong. Rivers meander, but they don’t generally turn right and left so sharply. And why should we see parallel zig-zags? This doesn’t seem to fit with a river channel origin.

The particular location, as shown on the overview map below, is close to the dry Martian equator, on the edge of Medusae Fossae Formation, the largest field of volcanic ash dust on Mars.
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