Tag: Arsia Mons

The first glacial evidence found on Mars back in 2007

11:36 am

Glaciers on Mars?
Click for original image.

Cool image time! The picture to the right, cropped, reduced, sharpened, and annotated to post here, was taken on January 3, 2023 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows the eastern wall of what the scientists call a graben, a large depression caused when the ground inside the depression suddenly shifted downward.

The elevation difference between the high and low points is about 3,500 feet. The streaks on the lower half of the cliff wall are slope streaks, a phenomenon unique to Mars that remains at this moment unexplained. Though the streaks resemble avalanches, they do not change the topography in any way, have no debris pile at their base, and appear instead to be a stain that appears at random times of the year that fades with time.

What is intriguing about this picture however is the wavelike floor on its western half. At first glance these waves suggest some form of dust dunes or lava flows, but neither conclusion appears correct. Instead, we are looking at what was one of the first discoveries on Mars of what scientists have determined to be glacial features.
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Random Martian ridges on a lava plain

1:02 pm

Random ridges on Martian lava plain
Click for full image.

Cool image time! The photo to the right, cropped and reduced to post here, was taken on December 30, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). This was a terrain sample image, taken not as part of any specific research project but to fill a gap in the camera’s schedule and thus keep its temperature maintained properly. When the MRO team needs to take such pictures, they try to pick locations that might be interesting and previously unphotographed, but often the location is neither.

In this case this terrain sample captured a flat lava plain interspersed with sinuous ridges going in all directions. On top of this is a scattering of smaller impact craters, which obviously occurred after the lava had flowed and solidified.

What caused the ridges?
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Strange land forms on the flanks of Mars’ Arsia Mons volcano

1:24 pm

Strange landforms on the flanks of Arsia Mons
Click for original image. Click here for the context camera image.

Cool image time! The center of the photo to the right was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on September 5, 2021. For posting here I have rotated, cropped, and reduced it, as well as added to each side the lower resolution context camera image of this region.

The ground slopes downhill to the north. Make sure you click on the image to see the full resolution version. In only a few miles the terrain changes from a mound with small knobs to a smooth area with few knobs to a chaotic area where the larger ridges and knobs are the dominant feature, with hollows and canyons in between.

You should also take a look at the full context camera image. Just to the southeast of the above picture is a large depression that looks like it has been filled with lava, with its western rim covered by that flow. Scientists have taken a lot of high resolution pictures of this depression with MRO, trying to decipher its geology.
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Two skylights into connected Martian lava tube?

3:33 pm

Two skylights into a connected Martian lava tube?
Click for full image.

Cool image time! The photo to the right, cropped and annotated to post here, was taken on September 1, 2021 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). I have annotated it to note the two apparent skylights that appear aligned along a north-south depression.

The grade is downhill to the north. If you look at the full image you will see that this north-south depression extends for a considerable distance beyond the edges of the cropped image above, with that depression appearing to dissipate to the north into a series of parallel very shallow depressions, almost like the lava had flowed out of the tube and formed branching surface rivulets heading south.

The overview map shows that this tube is on the northern flanks of the volcano Arsia Mons.
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The crack that splits the giant volcanoes on Mars

2:34 pm

Source of Arsia Mons rille
Click for full image.

Cool image time! In the April download of new images from the high resolution camera on Mars Reconnaissance Orbiter (MRO) was the photo to the right, taken on February 23, 2021 and cropped and reduced to post here, of what was labeled as “Source Region of Possible Rille on South Flank of Arsia Mons.”

Arsia Mons is the southernmost of the string of three giant volcanoes that sit between Mars’ biggest volcano to the west, Olympus Mons, and Mars’ biggest canyon to the east, Valles Marineris. This depression is on the mountain’s lower southern flank, and likely shows an ancient resurgence point where lava once flowed out from beneath the ground to form a rill meandering to the southwest. Today there is no visible resurgence. The floor of the depression appears to be filled with sand and dust, with the surrounding slopes spotted with scattered boulders.

What makes this particular image more interesting is how, when we take a very wide view, it reveals one of the most dramatic geological features on Mars, the 3,500 mile-long crack that caused these three volcanoes, and is actually not obvious unless you know what to look for.

So we need to zoom out. Let us first begin with a mosaic of three wider MRO context camera images, showing the entire rille and the immediately surrounding terrain.
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Two pits at opposite ends of Mars’ big volcanoes

12:40 pm

Overview map

Regular readers of Behind the Black know that since 2018 I have regularly documented all the images of pits taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO). (See my last pit post in January for a full list of these previous articles.) The black dots on the map to the right shows the location of all the pits near the volcanoes Arsia and Pavonis Mons that have so far been highlighted here.

The two white dots are the two most recent MRO pits, and are the subject of today’s cool image. They also happen to be the farthest north and south pits so far documented. The southernmost pit, which I am saving till last, is the most interesting.
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The seasonal cloud over Arsia Mons on Mars

9:21 pm

Water-ice cloud over Arsia Mons
The cloud as seen in 2018.

Scientists have now documented the seasonal nature of the strangely elongated cloud that was first spotted in 2018 above the giant volcano Arsia Mons (the southernmost volcano of the three volcanoes east of Olympus Mons).

From their abstract:

We find that the AMEC [Arsia Mons Elongated Cloud] repeated regularly each morning for a number of months, and that it is an annually‐repeating phenomenon that takes place every Martian Year around the southern hemisphere spring and summer. The AMEC follows a rapid daily cycle: it starts to expand from Arsia Mons at dawn at an altitude of about ∼45 km, and for ∼2.5 hours it expands westward as fast as 170 m/s (around 600 km/h). The cloud then detaches from Arsia Mons and evaporates before noon. In previous Martian Years, few observations of this phenomenon are available because most cameras orbiting Mars are placed in orbits where they can only observe during the afternoon, whereas this cloud takes place in the early morning, when observational coverage is much lower.

They also state that they will outline their theories as to the cause of the cloud in a follow-up paper.

I can’t help wondering if it is related to other evidence that suggested past glacial activity on the western flanks of Arsia Mons. There are many pits surrounding this volcano, and many might contain residue ice. One wonders if, during the warm spring and summer months at dawn the arrival of the sun might cause this cloud to form, and then vanish as the day passes, just like the dew does on Earth.

That is my uneducated guess, and likely wrong. We shall have to wait for their theoretical paper for a more educated guess.

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The longest lava tube in the solar system?

9:19 am

A lava tube on Mars
Click for full image.

Before I delve into today’s cool image, I think it important to explain to my readers why I seem to post so many cool images from Mars. The simple explanation is that Mars right now is where almost all the cutting edge planetary research is taking place, and as a science journalist focused on space exploration I must go to that cutting edge. My dear readers know that I love variety (just consider the evening pauses on Behind the Black), but you can’t ignore the reporting of real discoveries simply to increase the diversity of one’s posts. This is too often what modern news outlets do, which is also why they often miss the real story.

Anyway, today’s cool image to the right, rotated, cropped, and reduced to post here, shows only a small section of what might be the longest lava tube in the entire solar system. Taken on May 5, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO), it shows a string of pits along a meandering depression coming down the northwest flank of the giant volcano Arsia Mons. The image was a follow-up to a July 2014 photo of the same location, and was taken to produce a stereo pair.

The feature strongly suggests a lava tube, with the pits being skylights into the meandering underground void. From top to bottom this section of the tube is a little over three miles long. Since there are lava tubes on Earth far longer, this one image hardly makes this the longest tube in the solar system.

The tube, however, extends off the image both at the bottom and at the top. Not many high resolution images have been taken in this area, so it is therefore hard to say how far the tube extends. Other nearby high resolution images in this area however have found similar lava tubes, which conceivably could be part of the same tube. The overview map below shows the relationship.
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Peering into a Martian pit

1:44 pm

Peering into a pit
Click for full image.

Cool image time! The science team for the high resolution camera on Mars Reconnaissance Orbiter last week released the above image of a pit to the west of the giant volcanoes Arsia and Pavonis Mons. The left image is without any adjustments in exposure. The right image has brightened the pit’s interior to bring out details in order to see what’s there. As planetary scientist Ross Beyer of Ames Research Center noted in his caption:

The floor of the pit appears to be smooth sand and slopes down to the southeast. The hope was to determine if this was an isolated pit, or if it was a skylight into a tunnel, much like skylights in the lava tubes of Hawai’i. We can’t obviously see any tunnels in the visible walls, but they could be in the other walls that aren’t visible.

Wider view of pit
Click for full image.

Because the image has been rotated 180 degrees, north is down. The northern wall of the pit appears to be either very vertical, or overhung. A tunnel might head north from here, but because of the angle of the photograph, this cannot be confirmed.

To the right is a wider look from the full photograph, showing the surrounding terrain, with north now to the top. In line with this pit is a depression that crosses the east-west canyon to the north. This alignment strongly suggests that a fault or fissure exists here, and that an underground void along this fissure line could exist. It also suggests that a deeper and larger void could exist below that larger canyon.

This pit, and the accompanying fissures, were likely caused by crack-widening along these faults, produced as this volcanic region bulged upward.

Map of knowns pits surrounding Arsia Mons

This pit is also one of the many many pits found near these volcanoes. The map to the right shows by the black boxes all the pits documented by the high resolution camera on MRO in the past few years, with this new pit indicated by the white box.

Beginning in November 2018 until November 2019 I was almost doing a monthly post reporting the new pits photographed by MRO. Since November however the number of new pit images dropped. This is not because every pit has been imaged, but because it appears they have completed their initial survey.

Below is a list of all those previous pit posts:
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The many pits of Arsia Mons

1:57 pm

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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More Martian Pits!

1:11 pm

More pits on Mars!

As I said in my last post in February showing recent pit discoveries on Mars, I could almost make this a monthly series. In the March image download from the high resolution camera of Mars Reconnaissance Orbiter (MRO) were three (maybe four) more pits, all likely skylights above lava tubes and all located near the giant volcano Arsia Mons in the region dubbed the Tharsis Bulge. The image to the right shows all three, with a possible fourth just northwest of pit #2 and visible in its full image. For the full images of the other two pits go here (#1) and here (#3). In all three cases, click on the “black & white map projected” link to see the full image with scale.

Overview map

The overview map on right shows where these three pits are located. If you compare this map with my previous overview maps from November 12, 2018 and February 22, 2019 you can see that while these pits are all found on the volcanic slopes surrounding Arsia Mons, they are all different pits. Moreover, the ten pits listed in these three posts are only a small sampling of the more than hundred already found.

Whether these pits are deadend sinks or skylights into underground lava tubes that connect is at this point unknown. It would be a reasonable speculation to assume that some are deadends, and some link to extensive tubes of varying lengths. It would also be dangerous. Mars is alien. While the geology will be based on the same physical laws found on Earth, the lighter gravity is going to produce things differently.

The three images above however do show some intriguing details.
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Another batch of caves/pits found on Mars

1:10 pm

Four new pits on Mars

Overview of February 2019 pits

In the past year the monthly image releases from the high resolution camera on Mars Reconnaissance Orbiter (MRO) archive have frequently included newly discovered pit entrances. Each time I have written posts highlighting these new pits, in June, July, November 2018 and January 2019. In fact, this is happening so frequently I could almost label it a monthly update!

The November release imaged three pits found on the southern flanks of Arsia Mons. The January 2019 release found several north of the volcano, two of which are very close to the two middle new pits highlighted above. The February release, which is the focus of this post, included four more pits, shown above, all located north and west of Arsia Mons, as shown in the overview map to the right.

Pits 2 and 3 above appear to belong to a cluster of pits all located in the general area between Arsia and Pavonis Mons. (You can see their uncaptioned releases here and here.) Most sit alone on a flat somewhat featureless plain. Sometimes there are flow features nearby, but each pit usually seems to sit unique and unrelated to these other faint features.

Pit 1 is very intriguing in that it sits amid a very long chain of pits and canyons, all aligned, as shown in the image below and to the right.
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Volcanic vent between Arsia and Pavonis Monsa

1:14 pm

volcanic vent on Mars

Cool image time. The photo on the right, rotated, cropped, and reduced to post here, was taken in September by the high resolution camera of Mars Reconnaissance Orbiter (MRO) and was part of the November image release. Click on the image to see the entire photograph at full resolution.

The uncaptioned release dubs this feature as “Small Eruptive Vents South of Pavonis Mons.” In truth, these vent pits are located almost exactly the same distance from both Pavonis Mons, the middle volcano in the line of three giant Martian volcanoes, and Arsia Mons, the southernmost of the three.

The image is interesting for several reasons. First, note the bulge surrounding the vent, making this look almost like a miniature volcano all its own. In fact, that is probably what it is. When it was active that bulge was likely caused by that activity, though it is hard to say whether the bulge was caused by flow coming from out of the vent, or by pressure from below pushing upward to cause the ground to rise. It could even have been a combination of both.

To my eye, most of the bulge was probably caused from pressure from below pushing upward. The edge of the bulge does not look like the leading edge of a lava flow. Still, this probably happened so long ago that Martian wind erosion and dust could have obscured that leading edge.

That this is old is indicated by the dunelike ripples inside the large pit, and the pond of trapped dust in the smaller pit. Because of the thinness of the Martian atmosphere it takes time to gather that much dust, during which time no eruptions have occurred.

One more interesting detail: If you look at the pits in full resolution, you will see that, based on the asymmetrical wind patterns between the west and east rims, the prevailing winds here are from the west. Located as it is just to the east of the gigantic saddle between Arsia and Pavonis Mons, this wind orientation makes sense, as a saddle between mountains tends to concentrate the wind, much like a narrowed section in a river produces faster water flow and rapids. As for why the wind blows mostly from the west, my guess (which should not be taken very seriously) is that it is probably caused by the same meteorological phenomenon that causes this generally on Earth, the planet’s rotation.

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More Pits on Mars!

3:30 pm

Pits near Arsia Mons

Cool image time! In the November image release from the high resolution camera on Mars Reconnaissance Orbiter (MRO) were three images, dubbed by me in the collage above as number one, number two, and number three, showing pits south of Arsia Mons, the southernmost volcano in the chain of three giant volcanoes to the east of Mars’s largest volcano, Olympus Mons, and to the west of the Marineris Valles valley.

Mars overview showing pit locations

The image on the right provides the geographical context of the three pits. They are all south of the volcano on the vast lava flow plains that surround it. The location of pits #1 and #2 is especially intriguing, on the east and west edges of what appears to be a large lava flow that had burst out from the volcano, leaving a large lava field covering a vast area several hundred miles across just to the south. You can also see a similar large lava field to the north of the volcano. Both fields appear to have been formed when lava poured through the breaks created by the fault that cuts through the volcano from the northeast to the southwest.
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Intriguing water-ice cloud on Mars

9:41 am

Water-ice cloud over Arsia Mons

An extended water-ice cloud has formed recently on the downwind side of the large Martian volcano Arsia Mons. The image above, cropped to post here, was taken by Europe’s Mars Express orbiter, and shows the cloud extending westward from the volcano.

In spite of its location, this atmospheric feature is not linked to volcanic activity but is rather a water ice cloud driven by the influence of the volcano’s leeward slope on the air flow – something that scientists call an orographic or lee cloud – and a regular phenomenon in this region.

The cloud can be seen in this view taken on 10 October by the Visual Monitoring Camera (VMC) on Mars Express – which has imaged it hundreds of times over the past few weeks – as the white, elongated feature extending 1500 km westward of Arsia Mons. As a comparison, the cone-shaped volcano has a diameter of about 250 km.

… Mars just experienced its northern hemisphere winter solstice on 16 October. In the months leading up to the solstice, most cloud activity disappears over big volcanoes like Arsia Mons; its summit is covered with clouds throughout the rest of the martian year.

However, a seasonally recurrent water ice cloud, like the one shown in this image, is known to form along the southwest flank of this volcano – it was previously observed by Mars Express and other missions in 2009, 2012 and 2015.

What the article does not mention about these seasonal water ice clouds is that they are thought to be related to the evidence of past glaciers on the volcano’s western slopes. Some scientists believe that significant underground ice, left over from those glaciers, is what causes the clouds.

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A spectacular collapse feature at Arsia Mons

3:55 pm

Collapse at Arsia Mons

Cool image time! This post could be called an update to my January 8th post, Exploring Arsia Mons. In that post I had compiled together the ten images of Arsia Mons, the southernmost volcano in the line of three giant volcanoes on Mars, that JPL had highlighted over several weeks in early January.

Today, I decided to do some of my own exploration of some of the many images taken of Arsia Mons by all of the Martian orbiters. My goal had been to explore the volcano’s western slopes (an area that had not been featured in the JPL releases) because that is the area where research has found evidence of past glacial activity as well as seasonal water clouds. I haven’t finished that survey, but in the process I came across a spectacular image of a collapse that had been visible in image nine of the January 8th post, but did not stand out there because of the lighting. The image on the right is that better image, cropped to focus in on the collapse itself.

The material at the base of the wall resembles piled up mud, which suggests this collapse is a Martian version of a mud slide. If so, it also suggests the presence of liquid. At the same time, the muddy look might not be from liquid but because of the lighter Martian gravity causing avalanches to be appear different there. The light gravity means material is not as dense, so when it collapses it might break apart more easily into a sandy type flow.

I am only an amateur geologist, so my theories here should not be taken very seriously. Nonetheless, I am sure there are planetary geologists who have looked at this closely because of the information about Martian geology that they can glean from it. I’d be curious to hear their thoughts.

Meanwhile, my exploration of the western slopes of Arsia Mons will continue. In Pioneer the science fiction book I wrote in the early 1980s (now available), I placed my Martian colony in Mangala Valles, a meandering canyon to the west of Olympus Mons that feeds out from the higher southern regions into the lower northern flat plains where even then some scientists thought an ocean might have once existed. My thinking then was that this might be a good location to find underground water. It now appears, with our greater knowledge, that the slopes of the volcanoes themselves might be more promising, and I am curious to find the most likely places in this region where a future colony might end up.

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Exploring Arsia Mons

2:01 pm

Master index

In November over a period of two weeks the Mars Odyssey team posted ten images of Pavonis Mons, the smallest of the aligned three giant volcanoes just to the east of Olympus Mons, the largest known volcano in the solar system. I then made all of those images available in a single link, with some analysis.

They have now done the same thing for the southernmost (and possibly the most interesting) of those three aligned volcanoes, Arsia Mons. From the first image below:

Arsia Mons is the southernmost of the Tharsis volcanoes. It is 270 miles (450km) in diameter, almost 12 miles (20km) high, and the summit caldera is 72 miles (120km) wide. For comparison, the largest volcano on Earth is Mauna Loa. From its base on the sea floor, Mauna Loa measures only 6.3 miles high and 75 miles in diameter. A large volcanic crater known as a caldera is located at the summit of all of the Tharsis volcanoes. These calderas are produced by massive volcanic explosions and collapse. The Arsia Mons summit caldera is larger than many volcanoes on Earth.

In other words, you could fit almost all of Mauna Loa entirely within the caldera of Arsia Mons.

The image on the right above is the master index, annotated by me to show the area covered by each image. The images can accessed individually below.
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Europe’s Trace Gas Orbiter detects clouds over Martian volcano

9:31 am

Europe’s Trace Gas Orbiter (TGO) has detected clouds over the western slopes of the giant Martian volcano Arsia Mons.

This is not a new discovery, merely a confirmation of many past observations, all of which suggest that water-ice glaciers once flowed down those western slopes, and that some of that ice remains trapped in underground caves and lava tubes there. Undeniably this region appears at present to be the most valuable real estate on Mars. It has caves where the first colonies can be more easily built. Those caves likely have water in them. And the location is near the equator, which is easier to reach and also makes the environment somewhat less hostile.

TGO is presently slowly aerobraking itself down to its planned science orbit, which it is expected to reach in 2018.

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Finding caves on Mars

5:40 pm

A new study of pits on Mars has isolated one particular type of pit that has all the features of an Earth-like cave entrance, with a large number located in the regions around the giant volcanoes where evidence of past glacier activity has been found. From the abstract:

These Atypical Pit Craters (APCs) 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 usually greater than 0.3 (which is an upper range value for impacts and bowl-shaped pit craters) and can exceed values of 1.8. Observations by the Mars Odyssey Thermal Emission Imaging System (THEMIS) show that APC floor temperatures are warmer at night and fluctuate with much lower diurnal amplitudes than nearby surfaces or adjacent bowl-shaped pit craters.

In other words, these pits are deeper with steeper and overhanging walls that suggest underlying passages. They also maintain warmer temperatures at night with their day/night temperatures changing far less than the surface, similar to caves on Earth where the cave temperature remains the same year-round.

The study’s most important finding, from my perspective, was the location of these pit craters.
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India extends Mangalyaan’s mission by six months

9:20 am

Western slopes of Arsia Mons

Having successfully completed its nominal six month mission and continuing to operate perfectly, ISRO has extended the mission of India’s Mangalyaan Mars orbiter for another six months.

Take a gander at the images the orbiter has been sending down. Quite impressive. The cropped image on the right shows the western slopes of the giant volcano Arsia Mons, with white water vapor hovering above those slopes. (Click on the image for the full resolution version.) The water vapor is significant because scientists believe that this region once had many glaciers, and that much of that water is still present and trapped below the surface as ice, possibly in many of the caves that are there. The vapor’s presence, a routine occurance here, strengthens this theory.

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New images from Mangalyaan

10:18 am

Arsia Mons

Indian scientists have released a new set of color images taken by their Mars orbiter, Mangalyaan.

The image on the right is of Arsia Mons, one of the three giant volcanoes to the east of Mars’ biggest volcano, Olympus Mons. Arsia Mons is important for future manned colonization, as there are known caves on its western flanks. In addition, those western flanks show solid evidence of past glaciers, which means that it is very likely that those caves will harbor significant quantities of water-ice, making settlement much easier.

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A place on Mars that was possibly habitable only 200 million years ago.

9:43 pm

A place on Mars that was possibly habitable only 200 million years ago.

This article discusses the possibility of liquid water from the melting of the glaciers that scientists think once covered the western slopes of the giant volcano Arsia Mons. I have also written about this area in an article I wrote for Sky & Telescope last year on exploring caves in space. It is thought that there might be caves here in which some of that water from those glaciers might still be found.

As one scientist is quoted as saying in this article, “Arsia Mons would be the next place I would want to go.” Like the south pole of the Moon, it likely has all the ingredients for establishing a habitable colony.

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