First Halo Taken From Martian Surface By The NASA Mars Perseverance Rover, 15th December 2021

On the 15th December 2021, history was made when the Mars Perseverance Rover photographed the very first halo from the surface of Mars. The three images shown below are from a set taken from image series Sol 292 available on the NASA Perseverance Rover website,

https://mars.nasa.gov/mars2020/multimedia/raw-images/

Whilst technically it is not the first Martian halo, that accolade having been given to a subsun photographed from orbit by the Mars Global Surveyor satellite in January 2006, it is the very first to be taken from the surface of a planet other than Earth.

So what kind of halo are we looking at?  In the Martian atmosphere, both water and CO2 ice crystals are present. Taking the wide angle distortion of the Navcam lens into consideration, space artist Donald E. Davis who first noticed the halo in the Perseverance image archive wrote on Twitter that it "appears roughly consistent with a 22.5 degree radius". In all likelihood, the halo formed in water ice clouds rather than CO2; if the halo had been formed by CO2 crystals, then the radius would have been larger than what we observe. Likewise, we also have brightenings on opposite sides of the halo which are probably consistent with diffuse tangent arcs.

Image processed by Nicolas Lefaudeux.

Donald Davies has done some truly excellent work recreating the full halo from the separate images and has even produced a superb all sky reconstruction which has all the hallmarks of becoming iconic. You can find his ground-breaking work on Twitter here:

https://twitter.com/DDAVISSPACEART/status/1471823686332157953?t=gXNsEisXdDx9u3iofwNLZA&s=19

Image processed and manipulated by Donald E Davis.

Image processed and manipulated by Donald E Davis.

We sincerely hope that this will be the first of many Martian halos that will be captured by the Perseverance Rover and that this will open up a whole new field in halo science.

Major Update - 28th December 2021

Since posting the news about the discovery of the first Martian halo, Nicolas Lefaudeux returned to the Mars Rover archive to see whether he could identify further previously unrecorded halos. The results of his search are staggering. Besides the initial ground breaking Sol 292, he has discovered a further seven Martian halos of varying quality and intensity. These are Sol 145, 193, 249, 285, 289, 290 and 303. These confirm that both Sol 292 was not an isolated event and also that halos on Mars are a relatively common occurrence. All images presented below processed by Nicolas.

Sol 145

Sol 193

Sol 249

Sol 285

Sol 289

Sol 290

Sol 303

Sol 303

Two Displays in Åre, Sweden 8th & 14th November 2021

We present a guest post by Minna Kinnunen showcasing two really nice displays she was fortunate enough to observe at the ski resort in Åre, Sweden. 

First display – 8 November 2021. 

The weather forecast promised a few degrees freezing and blue skies, but the only problem was that when I looked out the window in the morning, it was most definitely overcast with the clouds hanging low. Then it dawned on me that this could well depend on the altitude and/or the snow cannons working at full (with Åre being the biggest skiing resort in Sweden), and my experience in these conditions is that if I make my way up the mountain, the blue sky will appear. 

The circumzenithal arc was beautiful but the only way I could capture it with my 24mm lens was to take two horizontal photos and stitch them together in Photoshop to show the whole thing. Parhelia are strong, upper tangent arc and sunvex Parry are a bit fuzzy and there's even a faint Moilanen arc.

I drove to Ullådalen just outside Åre and sure enough, I saw some pale blue sky above me as I parked even though the landscape otherwise was still shrouded in fog/ice crystals. Early on in my hike I saw the halo, just a ring around the sun but exciting nonetheless! 

At this point the halo was at its absolute best, a very distinct display. Really a pity I couldn't capture it in its entirety with my 24mm lens.

The further out I got, the thinner the diamond dust and the clearer the halo. And then it wasn’t just the ring around the sun, it was another ring around the sun and it was a ring across the entire sky and it was pillars and it was arcs, quite simply the most stunning halo display I had ever seen. I really had no idea what I was looking at beyond “a halo” but I knew it was special for sure so I tried to shoot it the best I could, considering that I only had a 24-105 mm lens with me and 24 mm was barely enough to contain the 22° halo. 

All I could do was to attempt to capture the details. The pillar from the parhelion is very strong here, is it a Schulthess or Lowitz arc or something else?

Later in the afternoon but well before actual sunset the sun disappeared behind the mountain, but as a parting gift it gave me a beautiful display of upper and lower pillar, upper tangent arc and Parry sunvex. 

As the sun started to disappear behind the mountain, the upper tangent arc and Parry arc became clear. Even the helic arc is still visible.

Since I didn't know much about halos at this point, I thought the white pillar 120° from the sun was actually part of a fogbow. As I already have some nice pictures of fogbows, I didn't  shoot it until the very end as an afterthought when it had alsmost disappeared. The full 360° parhelic circle had been visible earlier.

I learned those names afterwards as I was studying my pictures and I also thought I identified the 46° halo, but it’s probably a supralateral arc? My biggest question mark however is the pillar going down from the parhelion, I am calling it “bisolpelare” in Swedish which is a direct translation of sun dog pillar, but maybe we’re really talking about a Schulthess or Lowitz arc? 

I got out of the mountain's shadow for a brief moment, the parhelion and parhelic circle are still very strong.

I made a short film on the trip https://youtu.be/PRT3Lf_WPFM, the footage gives more information than my still pictures. I made an attempt at naming all the halo components, I realise now that I’m probably wrong about a couple of them so I will need to update the video! 

Gear: 

- Sony A7C + 24-105/4

- Pictures are taken between 10.33 and 14.23 

- Sun at 8.52 degrees for the first picture and 4.74 for the last, 9.96 degrees at transit 

- Altitude for shown pictures 730-800 meters 

Second halo – 14 November 2021

This is the second halo as I started going up the piste. Amazing upper tangent arc and sunvex Parry with a fairly distinct suncave Parry. The supralateral arc is more colourful now than the last time.

Less than a week later the weather forecast once again promised cold weather and sunshine. Of course, I had to go back to Ullådalen to see if the proverbial lightning indeed strikes twice, but as I parked my car it didn’t look quite so good. I did see a stunning upper tangent arc and Parry arc though and now I actually knew what they were, having read about halos all week. 

A little bit higher up the diamond dust is very thin and just about all that remains are the spectacular arcs above the sun.

This time I went to the opposite direction from the earlier trip, up the piste towards the small peak of Rödkullen at the foot of the mountain of Åreskutan. The diamond dust that wasn’t very thick to begin with got thinner with every step and the halo faded with it. Up on Rödkullen the only hint of anything exciting going on was the rainbow colours I saw on the mountain side opposite the sun. 

The irridescent (?) fog opposite the sun.

Back by the car the halo became visible again. Since I now had a better idea of the halo types, I had a look around to see if I could find anything that I haven’t already seen. It didn’t look that good though so I figured that the show was over, time to go home. However, as I was driving down the road and the diamond dust got thicker, the halo made a glorious comeback. I tried to find some nice spots to shoot it, got too far down on the road and turned back. 

Going back up with the sun on my back, I saw it – the anthelion! I could barely contain myself, just jumped out of the car and shot it right there in the middle of the road. Which was just as well, because the anthelion turned out to be very short-lived, it only took a few minutes and it was all gone. 

What an unexpected and welcome sight, the anthelion and anthelic arc!

I drove the road up and down twice more without discovering anything new. Down the road the diamond dust was too thick and up it was too thin, the line in between was quite sharp. 

On my way home though I saw the halo by the Åresjön lake, so I took one more shot of the halo to cap off an absolutely amazing week of halos. 

On the opposite side of the anthelion, this halo.

The larger ring – be it 46° halo or supralateral arc – is white in the first halo but coloured in the second. Is it the same thing or a different type? 

Even a Tape arc made an appearance.

Gear: 

- Sony A6300 + 10-18/4 (15-27 mm effective) 

- Pictures are taken between 10.07 and 13.37 

- Sun at 5.86 degrees for the first picture and 5.81 for the last, 8.33 degrees at transit 

- Altitude for shown pictures 665-785 m. 

//Minna Kinnunen – vandrafotaleva.nu 

Update - 10th December 2021

When Minna's post was originally published, I was working on the assumption that we were dealing with a 120 pillar. However, after processing the image in several different ways, I noticed something unusual on either side of the pillar. I was fairly sure that the feature was real and not an artefact so I reached out to the halo community for suggestions as to what it might be.

'Mikkilä's soul'

Almost immediately Marko Riikonen recognised it for what it was, 'Mikkilä's soul' or Mikkilä's diffraction pillar. More details here,

https://www.atoptics.co.uk/fz742.htm

https://www.taivaanvahti.fi/observations/show/46324

Marko commented that whilst the diffraction pillar occurs reasonably frequently in spotlight displays, to the best of his knowledge, this is only the second time it has been observed in a solar display, the first being in Sotkamo, 2015. Minna checked her Photographers Ephemeris and further confirmed that the pillar was indeed located at the anthelic point.

Position of diffraction pillar as shown on Photographer's Ephemeris

Final irrefutable confirmation was provided by Nicholas Lefaudeux who has very kindly processed the image and managed to bring out the delicate coloured fringing of the phenomenon.

Processing by Nicolas Lefaudeux

As an amusing aside, when Minna was shooting the display, she didn't realise what the 'halo' she was seeing was and only took one photograph of it. Later during the editing process, she wasn't too impressed with the image and actually deleted it! However, on further reflection she rescued it from the trash and in so doing joined a very select club!


Alec Jones

Major Halo Outbreak in Southern China, Apr 29 ~ May 01, 2021

A major halo outbreak stunned sky enthusiasts in multiple Southern China provinces between Apr 29 and May 01, with a surprisingly wide variety of high cloud halos. Even though nothing particularly rare were discovered, it's still worth sharing some of the highlights as eye candies to the international community. 

(We were completely overwhelmed by the huge number of online records and submissions during the outbreak. Special thanks goes to JI Yun, who spent days going through thousands of cases and identifying the noteworthy ones. All photos in the post are shown with permission. Minimal post processing applied.)

Mid-to-high Sun Parry Arcs

Likely China's best mid-sun parry arc record to date, taken by PENG Lijuan in Hunan Province on Apr 30. 

Taken by JIANG Simin in Hunan Province on Apr 30. Note how the lower suncave parry arc becomes a full circle under the 70° high sun, and cuts right through the parhelic circle and Wegener arc. What a sight to behold. 

Helic Arc

Helic arc has been extremely rare in China, both in high clouds and diamond dust. The previous two high cloud cases were forgettable at best - barely visible in heavily processed raw images.

Finally during this outbreak, some good quality high cloud helic arcs were photographed, with mobile phones!

Taken by PENG Lijuan in Hunan province on Apr 30. There seems to be traces of lower Lowitz arc tangent to the left side of 22° halo too.

Taken by JIANG Simin in Hunan province on Apr 30.

Odd Radius Column Arcs

Taken by ZHANG Yifei in Sichuan province on May 1. 9°, 20°, 24° and 35° column arcs are all sharp and vivid. Note how the 20° and 35° column arcs differ from their random counterparts by being half circles.

Taken by LIANG Yongqiang in Guizhou province on May 1. Column arcs in this one are not as intense as the Sichuan photo. However, look carefully for the 35° column arc which cuts through a weak Wegener arc inside the parhelic circle. Such combo doesn't come easy!

Airborne Odd Radius Plate Arcs

Upper 20° and 35° plate arcs are very common during summer months in Southern China. Their lower counterparts, on the other hand, are far less frequent. In fact, the number of sightings we logged before this outbreak is zero. The void is now filled, finally.

Taken by BAC onboard a Zhuhai - Shanghai flight, on May 1. 9°, 20° and 35° lower plate arcs dominate the show. 24° lower plate arcs are probably there too, as well as weak 9°, 20° and 35° column arcs.

JI Yun & JIA Hao

The first Ounasvaara arc in high cloud photographed

 The Ounasvaara arc stage of the display. The 46° contact arc is good here, too. File: 46 DSC_7720_stitch-1

 

Discovered in a spotlight display in 2007, we now have the first case of a high cloud Ounasvaara arc. The halo came up in a big display that Leesa Brown photographed in Kissimmee, Florida, on 23 April this year. She took about 1200 photos between 18:12 and 19:04 and it's good she didn't stint on film, otherwise the narrow occurrence window for the Ounasvaara arc at 19:00-19:02 might have been missed. It helps also that she photographed wide enough to cover the sky high up beyond the circumzenith arc.

The same goes for the display's Kern arc, which visibility window (at least where you need not to guess whether it is there) was equally short at 18:38-18:39. While Kern arc has been photographed in high clouds a handful of times, this is only the second time that it is intense enough to appear in single images.

 

The Kern stage of the display. Sun elevation 16 degrees. File: 28 DSC_7359b_stitch-2 

 

The display had also Lowitz arcs curving down from both Parry arcs, a highly unusual combo. Normally we see from Parry-Lowitz oriented crystals only the Lowitz arc associated with uppercave Parry arc, that is, the upper Lowitz arc. Sightings of the one associated with the uppervex Parry arc, the circular Lowitz arc, are very few. Actually, should anyone know such observations, it would be nice to hear.

 The two Lowitz arcs curving down from their Parry arcs show up nice here. In the cza region there is some stitch misalignment. File: 42 DSC_7666_stitch-1

And then there is an exemplary 46° contact arc straight above the sun. More often 46° contact arcs are seen in diamond dust, high cloud cases are very rarely encountered.

All and all, this display in Kissimmee on 23 April ranks among the top photographed high cloud halo complexes. Its uniformity and celestial span might have been a bit compromised, but the conglomerie of high rarities makes up for it. 

We asked Leesa to give her first hand impressions of the display, here is what she wrote:

On Friday, April 23 2021, I had been out all day with a friend, doing some nature photography. I kept seeing a lovely 22 degree halo, and bits of other interesting sky phenomena, and snapped photos of them between watching birds and other wildlife.

I got home around 6:00 pm, and all I wanted to do was sit down and rest. But there was a halo and a lovely display going on outside, so I did what any sky-loving photographer would do - I dropped my stuff inside the door, and went back outside to capture whatever I could.

When I'm photographing displays like the one I saw that Friday night, my one overriding feeling is always the same - wanting to turn to someone and say "Do you SEE that??"

That's why I'm so happy to have found some of the people I've met online since that day. My friends and family like the photos of displays like these, but they don't truly understand the joy of finding new arcs you've never seen before, or the beauty of seeing these in person. 

Birders call your first sighting of a particular species of bird a "lifer."
This display turned out to be more than that for me - probably a once in a lifetime event.

And now, with the help of Marko Riikonen, Alec Jones, and a few others, I can finally turn to the people reading this and say "Do you SEE that?"

I'm glad there's someone there to see it this time.

Thank you!

 

All Leesa's photos and the panoramas she made are in Google Drive should anyone like to take a look:

https://drive.google.com/drive/folders/1pF97EiF_3v29usSxzyZhwmJXaa7nFE4a?usp=sharing

Color versions of the three panoramas above, plus one more panorama, are at the end of the post. The helic arc, which is largely lost in the b-r images, shows up nice in these versions. Also, the Kern arc can be discerned.

 

 A single image from the Ounasvaara arc stage, worked by Alec Jones using DStretch software.

 

 

Finally, above is a simulation for the display's Ounasvaara arc stage. Two Parry populations were needed to get it right. Ounasvaara arc needs triangular crystals, but such crystals make only uppervex Parry, not uppercave Parry. So, another population of slightly tabular crystals was necessary to summon up the latter. It is a bit strange combination of Parry populations and probably does not reflect the full truth as the unevenness of high clouds likely complicates things here. Arrows from top down: Kern arc, Ounasvaara arc, 46° contact arc, upper Lowitz arc and circular Lowitz arc.

The simulation was done with Samuli Vuorinen's Haloray software and then turned into b-r. There was a problem with the Parry halo intensities in the software, which is why the right side arm of the Ounasvaara arc is brighter than the left. Now I just heard from Vuorinen the bug has been fixed. The parameters are displayed below in the HaloPoint user interface as Haloray doesn't come with such at-a-glance view.

 

Addendum on 9 May 2021

The Kissimmee display just gets bigger. Reima Eresmaa spotted from the Kern arc stage panorama (28 DSC_7359b_stitch-2) also Hastings and Wegener arcs. Below is shown the single photo (DSC_7377) containing those arcs, compared to a simulation. Subhelic arc would be expected as well in this massive display and the white stripe under the Wegener arc looks like a potential candidate. But the otherwise pretty well matching simulation does not support this: the stripe is too high up in the photo. So unless I have made a mistake in correlating the simulation and the photo, it must be regarded as a wispy cloud strand. Sun elevation for the Haloray simulation is 16 degrees. Alec Jones enhanced the photo.

Hastings arc is always a great catch, probably no more than half a dozen high cloud cases are known.

Reima Eresmaa has worked a simulation that gives a good match with all halos, including subhelic arc. His simulation with the photo is added below. See more in comments.

Subhorizon odd radius halos – Rovaniemi 9/10 February 2021

 

The weather was cold with a light breeze from the west, so I headed east to Jokkavaara gravel pits to check whether the reach of the diamond dust extended that far. The three previous times I have had odd radius sub-plate arcs were at these pits, all in winter 2016/17, and I was thinking maybe now it is this winter's turn for the Jokkavaara magic. 

There was diamond dust at Jokkavaara, and as the image above shows, it was indeed of the pyramid crystal kind: inside the subparhelia we see pretty decent sub-18° plate arcs. This is an average stack of the eight best photos showing the halo. They are included in collage below which is a larger set of successive 30 s exposures showing the changes in the display. I made also a video of these photos (one or two last photos are excluded in it).

As these photos show, the sub-18° arcs were fickle in appearance, alternating with subparhelia in successive frames. No wonder I was uncertain about them visually. At one point a broad effect was visible. I take this to be the time when in photos both sub-18° arcs and subparhelia appear. Thus my visual appears to tell that they were then in the sky simultaneously, not separately during the 30 seconds exposure.

 

 

And so on to some simulations. For starters, let's mention that I was unable to simulate the vertically greatly elongated shape of the subparhelia and sub-18° arcs seen in many photos. Increasing crystal tilts didn't lengthen them.

But in three successive photos, starting from the middle image on the third last row in the above collage, the sub-18° arcs are actually quite compact. Because the pyramid crystal orientations have likely been least unstable at this stage, a stack of these three photos is what I decided to compare the simulations with.

The single pyramid makes only sub-18° arcs and a weak sub-23° arc, which would seem to explain the photo pretty nice. But the spot on the right side of the display (marked with an arrow in b-r) is not reproduced by this crystal. If we use instead a double pyramid then we get a matching spot which, with the pictured crystal, is contributed equally by overlapping 35° arc and sub-35° arc. A different double pyramid shape could also have been chosen to make either one.

The double pyramid makes also sub-20° arc, 18° arc and 23° arc, and while there may be a suggestion of the last one in the photo, the first two are not there. Some adjustment on pyramid proportions may get rid of the sub-20° arc, but that will just make 20° arc emerge, which is not seen in the photo either. And the 18° arcs stick there always with the double pyramid. So this kind of crystal neither satisfyingly explains the display. 

Concerning the 35° spots, it is good to read also what has been written on them concerning another display on 4/5 January 2017 (under the collage image with simulation parameters). There seems to be a possibility even for an impostor.

The raypaths are for sub-18° arc (left) and sub-35° arc (right). The simulations have also normal plate population to make parhelia and subparhelia. Light source elevation for simulations is 27 degrees. 

 

An earlier stage of the display, as shown below, seems to contain the 35° spots as well. These are the first eight photos I took. In addition, I would say a there a pretty certain 23° arc and the b-r appears to show 18° arc on the left. The sub-18° arcs are also there. While setting up the tripod I thought of seeing them and was nervous whether they would still be present when I was ready.

The first eight photos average stacked, not included in the collage above.

 

 

Let's show one more stack. It is made of the photos that I took after having a break in the car. I needed to warm up the lens that suddenly got frosted after the best stage (I must have breathed on it). The display had lost its verve by this time and in the photos of this second set are only faintest suggestions of sub-18° arcs. But the 23° arc seems to be here yet again, and maybe even a little separation from the circular halo can be imagined. 

 

 

 

After yet another break in the car I got a set of 24 photos before the hid started flashing as a sign of the 55Ah car battery having run out. The stack of this set has no odd radius halos anymore and I have not shown it here. Although I had another full battery which would have kept me going for two or even three hours more of effective burning time, I called it a wrap. I know – I should have continued until that battery, too, was drained. There would have been plenty of time as it was only 1 am and no indication that the weather would be failing. There is no excuse for this lapse of form.
 

A few more simulations for the end. In the simulations below the light source elevation goes from 26 to 29 degrees in one degree steps. This is to show how close the 35° arcs and sub-35° arcs are to each other at this elevation range. I ended up using 27 degree elevation. There is probably room for that being off one degree both ways.

 

 

And for the future, two simulations to suggest what the view might look when pyramid crystals come equipped with the normal prism. The raypaths are for the two sub-9° arcs below the subsun. I forgot the normal plate population from the left hand simulation. Interestingly, it still has subparhelia.