Mastodawn

Phil Stooke Feb 13

The 'rises' and troughs form patterned ground, which forms in arctic regions over many years of seasonal freezing and thawing of ice in the ground. Thousands of years - but here on Mars we may have tens of millions of years of the process. Viking 2 didn't see that ice but we know it's there because HiRISE saw new craters form nearby, exposing ice which then slowly melts away - see this free access paper:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013JE004482

Phil Stooke Feb 14

So the lander was found by HiRISE - where is it exactly? This set of maps zooms in on the site. The parachute is not very visible, and maybe this identification is wrong. But the lander is certainly correct because rocks and other features around it can be identified in the panorama and the HiRISE image.
#mars #maps #viking2

Phil Stooke Feb 15

The panorama can be projected into a circular projection - a polar projection, except that I like to modify the radial scale in a way that more closely resembles a stereographic projection. It's easier to compare with a map if you do that. Here it is for Viking 2, with a HiRISE image to help locate a few features. Other features like the western ridges are shown on the previous post.
#mars #Viking2

Phil Stooke Feb 15

Here's an interesting perspective on what we are looking at in this area. The Moon's surface would look like this if we gave it a bit of an atmosphere so the finer dust could be blown away by the wind. Strip away the finer dust, let it accumulate in other places, and what is left is all the rocks buried in the regolith, and gravel between them. I know it might not be exactly true, but it's not too far off.
#mars #viking2

Phil Stooke Feb 16

Here is the HiRISE image of Viking 2 with an attempt to project the surface panorama onto it. It's not really very successful. Over the years I got better at this and by the time we got to InSight I think it worked very well (you can judge yourselves if we get that far in this story). The rocks are stretched into pillars by the projection, and later I worked to shrink the height of each rock individually. But not here. Still, it gives an idea of the nature of the site.
#mars #viking2

Phil Stooke Feb 17

Let's zoom in closer to Viking 2. Again we have a surface panorama projected onto a HiRISE image to show the character of the site. At this scale, closer to the lander, it works better, but note one problem. Rocks get elongated by the process but they should all extend radially out from the camera. Where they seem to swirl a bit I got my control points wrong. But you can only do so many iterations! Arida Fossa is 'dry ditch'.
#maps #mars #viking2

Phil Stooke Feb 17

Now we zoom in really close to the lander, and here the process works pretty well. Only one rock was so tall that it looked badly distorted so I shrank it down leaving a blank area behind it. I could have done more but didn't here. For InSight I did this for hundreds of rocks, hence my white hair. Lots of features have names here in the sampling area where we will see a lot of activity.
#maps #mars #viking2

Phil Stooke Feb 18

Now we can get into the details of this mission. The first event was the ejection of a shroud which covered the surface sampler during flight and landing. It bounced off a rock, moving it slightly, bounced off the ground leaving a mark and fell in view of the camera as these images show. I overlay one image on another and do a 'blink comparator' job - switching between them so any change is easy to spot. Got the idea from Clyde Tombaugh.
#mars #viking2

Phil Stooke Feb 18

After that the arm was used to scoop up a bit of soil for analysis in the biology experiments, looking for any signs of organics or metabolism. We are going to look at every arm operation.
#mars #viking2

Phil Stooke Feb 19

These images show more early activities by Viking 2. First, two more digs in the same area as last time, another biology sample and one for the x-ray instrument for mineral composition analysis. Next, four panels show activities at Bonneville Salt Flats. The first frame shows a flat platy structure interpreted as fine soil cemented by salts left by evaporating water (a caliche in geological terms). First a sample for the GCMS instrument.
#mars #viking2

Phil Stooke Feb 19

GCMS is the Gas Chromatograph Mass Spectrometer instrument looking for organics (carbon compounds) in the soil. They didn't find any. Then they took another sample for the x-ray fluorescence instrument. Finally we see a failed attempt to move a rock called ICL - Initial Computer Load. If commands from Earth were not received the pre-loaded ICL instructions would dig at that (then unknown) location, analyze a sample and transmit results. The arm would have hit the rock and failed.
#mars #viking2

Phil Stooke Feb 20

Now Viking 2 started to get a bit rough with the rocks around it. In the top sequence we see the rock Mr. Badger moved and then a sample taken from underneath it (which action moved the rock again). In the second sequence Bonneville is moved slightly, but it rolls back to its original position. Then we have 4 frames of the rock Notch. It is pushed slightly to test it, then pushed more, and then a biology sample is taken from under its original position.
#mars #viking2

Phil Stooke Feb 20

The idea with these moves is to take soil from a place where it has been protected from ultraviolet radiation and maybe cosmic rays, which would destroy organic molecules. The protected samples might contain organics or even life. Notice the purge pile in the bottom middle image - the scoop was emptied of whatever was in it before the biology sample was collected to avoid confusion with material not protected under the rock. We will see more of that tomorrow.
#mars #viking2

Phil Stooke Feb 21

This set of images takes us through the last few activities of Viking 2's primary mission (just before conjunction), and shows an area where several scoop purges were done, at different times during the mission. The top 4 frames show an area near ICL rock. First, a physical properties experiment tested surface hardness (and note small rocks dropped in a purge on sol 21). Then two samples were dug nearby for mineral analysis with the X-ray instrument.
#mars #viking2

Phil Stooke Feb 21

The 3 bottom images in the last post show an area close to the lander, too close for the arm to dig, so perfect for dropping debris from the scoop (purging). The first image is the very first picture taken by Viking 2, beginning while some dust was still in the air from the landing (making those streaks). By sol 38 a few small changes are apparent, but very small - a little rock, a dark spot where a soil clod fell. Blinking the images reveals them. The last image...
#mars #viking2

Phil Stooke Feb 21

... is from late in the mission, showing a few more small changes. There is one big change, existing rocks covered with dust. I labelled it with a query - wind-blown dust? - but it could have been a big purge.

That is the end of Viking 2's primary mission. Tomorrow we will see what the map looks like after all this.
#mars #viking2

Phil Stooke Feb 22

Here is the sampling area map after the primary mission ended. We will see the map change considerably in future. One thing I did not do is actually move on the map the rocks which were moved. I should have. Oddly, I see now that I did reduce the height of the rock Mr. Toad (like I did for Centaur) in the pre-sampling map but not here... consistency often eludes me!
#mars #maps #viking2

Phil Stooke Feb 22

Here is the same content in the geometry of a panorama. The purge area shown in yesterday's post is near the sol 21 purge area on the map.
#mars #viking2

Phil Stooke Feb 23

Viking 2's primary mission ended on sol 60, followed by a blackout period as Mars passed near or behind the Sun and communication was curtailed. The lander continued to collect weather and seismic data, and it was transmitted to Earth after conjunction (after sol 103). A seismic event may have occurred on sol 80 - the only likely one of the entire mission (Viking 1's seismometer failed). Most apparent seismic events coincided with wind gusts and are not counted as 'marsquakes'...
#mars #viking2

Phil Stooke Feb 23

... but there was no concurrent wind data with this one. However, it occurred at a time of day with little wind. This is not certain but stands as the only likely seismic event detected on Mars until the InSight mission decades later.

After conjunction the arm started work again. Here we see several actions near the rocks Notch and Doc. X-ray fluorescence spectrometer (XRFS) samples were dug out of the previous Biology 3 trench and a new area.
#mars #viking2

Phil Stooke Feb 23

The last 2 images show another XRFS sample collected near Mr. Badger. In all these cases the fine material was delivered to the instrument in the lander for analysis and coarser material was dropped to form a 'rock pile' near the new trenches. There were really very few rocks but a little collection gradually accumulated.
#mars #viking2

Phil Stooke Feb 24

Today we just have two images, a before and after - so just one event. This was the collection of a sample called Biology 4 for analysis in the suite of biology instruments. Viking 2 didn't do very much for quite a while now. There were problems with the arm which prevented sampling on sol 195. Winter was approaching and Viking 2, further north than Viking 1, had to enter a power-saving mode between sols 220 and 373. Right after that another failure prevented...
#mars #viking2

Phil Stooke Feb 24

... direct to Earth communication from the lander. Now it could only communicate via an orbiter. The planet was also throwing dust storms into the story. On sols 165 and 269 dust effects were detected, each time lasting for weeks. The nuclear powered landers were not affected as much as the solar-powered MER rovers were decades later, but it was another complication to consider. Tomorrow we will look at the sol 100-300 map.
#mars #viking2

Phil Stooke Feb 25

As suggested yesterday, there was not a lot of action for Viking 2 between sols 100 and 300, so this map does not have many changes since the last one. A few sample trenches, basically. Don't worry, that is going to change soon.
#mars #maps #viking2

Phil Stooke Feb 25

And the same content represented as a panorama.

We will get down to some serious work tomorrow.
#mars #viking2

Phil Stooke Feb 26

During the period we have just covered, winter for Viking 2, the lander took its first pictures of frost on the surface. We don't see many pictures like this because most landers have been at lower latitudes. Phoenix is the obvious exception, but Viking 2 did it first. These links show 2 images - but from later in the mission, the second winter.

https://www.planetary.org/space-images/viking2_frost_stryk

https://www.nasa.gov/image-article/viking-lander-image-of-ice-mars/
#mars #viking2

Frost at the Viking 2 landing site (super-resolution)

This image of frost on Mars has become iconic. Unfortunately, it is tiny, because it was obtained using Viking's low resolution mode and there was no high…

The Planetary Society

Phil Stooke Feb 26

Arm work with Viking 2 resumed after the winter slow period. Here we see a 'deep hole' being dug, as with Viking 1. The area is the same as in the previous two arm action images a couple of days ago. Multiple strokes of the arm were used to move material aside, trying to get deeper material, with XRFS samples picked up after trenching each time. 100 sols after each dig, more samples were taken at the near end of the hole.
#mars #viking2

Phil Stooke Feb 27

Another set of Viking 2 arm activities. Because I collect them spatially they are only chronological within a spatial set... if you see what I mean. The first 4 here are at the extreme right end of the sampling area. The scoop backhoe touched the surface and then dug a sample. On sol 479 it dug a sample for 'Physical Properties' - in this case sieving out the fine material and dropping the coarse material to see how many small rocks were in it (not many).
#mars #viking2

Phil Stooke Feb 27

Physical properties could cover a lot of things including bearing strength of the soil and sizes of particles. The next Phys Prop dig on sol 595 was dumped nearby to make a conical pile of soil. It would be imaged at intervals over several years to monitor wind erosion. The last 2 frames show another Phys Prop sample being dug to make another conical pile which we will see soon. Viking wasn't just about the obvious things, the chemical analysis and biology experiments.
#mars #viking2

Phil Stooke Feb 28

Here are some more activities at the Viking 2 site on Mars. At top, we see the arm moving a rock called Snow White, scraping the surface in the process. Then a sample is taken from the scuffed area for analysis. Next we see a conical pile of soil formed on top of a rock (this was dug out of the Phys Prop 2 trench from the previous post). Finally a 3rd conical pile was made near that same rock. We saw more of these at Viking 1.
#mars #viking2

Phil Stooke Mar 1

This map shows the Viking 2 sample field after 500 sols. Digs at the near end of Deep Hole which we have already seen happened after sol 500 so they are not shown. I quite like being able to see the sampling area evolving like this.
#mars #maps #viking2

Phil Stooke Mar 1

This is the same content as in the map just posted but shown as a panorama.
#mars #viking2

Phil Stooke Mar 2

We are coming to the end of Viking 2 activities with the arm. This set of before and after image pairs shows rather small events. First, on sol 502, a backhoe touchdown. The backhoe was a plate protruding under the scoop, which could be pulled through the soil to dig a trench like Deep Hole. It had a magnet on it which was imaged now and then to look for magnetic particles stuck to the magnet. This touchdown was one of those attempts to pick up particles.
#mars #viking2

Phil Stooke Mar 2

The sol 522 touchdown was done to... actually I don't know why it was done. The sol 559 touchdown was an attempt to chip Mr Mole - but it didn't, indicating that it was fairly hard. Nearby on sol 595 was a Physical Properties touchdown - the scoop was pressed down to test the bearing strength of the surface. Look at the result - the surface is not dusty but breaks up into platy chunks, probably cemented by salts left by evaporating water. They called it duricrust at the time.
#mars #viking2

Phil Stooke Mar 3

This is the last set of images of Viking 2 arm operations. In the top row we see two samples collected for analysis. The remaining images show several physical properties actions, the last of which was about scooping up soil and depositing it back on the surface to make a conical pile. That would be observed at intervals through the rest of the mission to check for wind erosion. I will say more tomorrow but it's late here and past my bedtime.

Phil Stooke Mar 4

Continuing from yesterday's post, those physical properties activities did various things. I don't know the purpose of Phys. prop 4, but it dug up fine-grained material and one buried rock. PP 6 at the bottom was supposed to measure surface strength but the result was lost somehow, not downlinked. PP 8 dug soil which was used to make Conical Pile 4. PP 9 was a surface strength test again and the scoop with its temperature sensor was left in the soil for a full day.
#mars #viking2

Phil Stooke Mar 4

After that the arm was parked and not used again. This map shows the sample area at the end of the mission.
#mars #maps #viking2

Phil Stooke Mar 4

And the same content in panorama geometry, as before.

There is not much more to say about Viking 2 but I do have one last treat for tomorrow.
#mars #viking2

Phil Stooke Mar 5

If you look back to Viking 1:

https://mastodon.social/@PhilStooke/115376798213914717

you will see a bit about the mirrors mounted on the arm housing on each Viking lander. The mirrors reflected an image of the surface just under the lander. By moving the arm slightly the reflected area could be changed and a mosaic could be constructed. Here are two mosaics for Viking 2, one from each mirror. At left a bit of the lander near the front left footpad shows a temperature sensor.
#mars #viking2

Phil Stooke Mar 5

At right in that image is a larger area of the surface showing the surface eroded by the landing thrusters. Mosaics like this are much easier to make today with modern image processing software than in the Viking period when they were constructed from printed images. This image shows the approximate location relative to the surface imaged directly by the cameras.
#mars #viking2

With that I will conclude this look at Viking 2's surface mission. I hope you enjoyed it - I think we have seen things that are a bit different from the usual coverage, and it's fun to re-live an older mission like this (well, it is for me).

Now we will move on to a new topic. This time it's back to the Moon. I want to look at what is happening now to select landing sites for Artemis missions, and earlier work for Constellation... and what Russia and China have been doing. Stay tuned...