Diamond sky: Remembering a fabulous frosty afternoon in Antarctica

I was with 30 other 'happy campers' at our field camp training course in October 2011. It was going to be a cold night (-30°C) but the afternoon was a pleasant -20°C, the sky was blue and the sun was 'high' in the sky (high at least for being 77°S...around 18° elevation). Around 3pm the sky started to become hazy and some hints of sectors of faintly coloured haloes started to appear around the sun with Castle Crag and Mount Terror in the background (Photo 1).

Photo 1: Sundog, Halo, Diamond Dust in front of Castle Crag, McMurdo, Antarctica (Photo: TJI)

Drawing 1: after Photo 1 (TJI) 

The haze became more obviously enveloping and was composed of tiny ice crystals called 'diamond dust'. So-called apparently because they look like diamonds under the microscope. As you will see, these are particularly awesome in terms of their optical effects and these are most dramatic when the crystals settle slowly in the breeze so that they are all oriented in a similar fashion.

As the icy dust came around us the most obvious thing to see was the parhelic circle that extended all the way around us (even looking directly away from the sun, though faintly). Then the sundogs shone out as the second brightest things in the sky after the sun, located at the left and right sides of the first halo. The second halo was fainter (see photo 2) at 46°from the sun. There were even two fuzzy patches marking out 'negative sundogs' located looking away from the sun, these are called 120° parhelia (drawing 2). At the top of the first halo there was an 'upper tangent arc' providing a mystical veil quality looking above the sun. 

Drawing 2: Dome reconstruction of optical phenomena seen (TJI)

Photo 2: Second halo and parhelic arc extending over Mt Erebus (TJI)

At first this was so spectacular that we didn't even notice that if you looked up at the top of the second halo, there was something quite magnificent. Photo 3 shows the inverted rainbow appearance of a 'circumzenithal arc' which smiles down at you from almost directly overhead. This arc circumscribes a point 90° above the angle of the sun and touches the second halo. Quite unbelievable if you are not expecting it (like me). Luckily I had just bought a 15mm wide-angle lens which was able to capture these all at once (Photo 3) since the angle of view is >90°.

Photo 3: 'Happy Campers' under diamond sky and a circumzenithal arc (TJI)

Over the course of 30 mins the diamond dust slowly dissipated and after an hour the show was over. I felt like I had been treated to a vision from (a very cold) heaven with these beautiful traces, arcs, colours drawn out all around us. Probably the closest thing I have had to a religious experience as it turns out. Coming from a mineralogical background I could not help but conjure up crystallographic analogies as the view was very much like being in the centre of a stereonets (used for stereographic projections...Drawing 2 is based on this concept). It was like we were inside a giant imaginary hexagonal ice crystal with rays of light bouncing around in a crazy magical kingdom!

In one of my photos I did notice that a sun pillar had formed at a later stage in the afternoon below the sun. These ice-related optical phenomena can also show many types of pillars and arcs. Here is an outstanding website on a wide range of optical phenomena: http://www.atoptics.co.uk/halosim.htm

These guys also provide an amazing piece of software called 'Halosim' which allows you to define different populations of differently shaped and oriented ice crystals. We tried this over the course of a morning and found that we needed four populations to explain the array of haloes I saw. 

1. 37% hexagonal plates oriented randomly ==> 23° and 46°haloes
2. 45% hexagonal plates dispersed 3 degrees on a vertical axis ==> parhelic circle, 120° parhelic spots and a one-sided circumzenithal arc.
3. 3% hexagonal prisms with 'Parry-style' orientation parameters ==> upper tangent arc and weak diagonals within the inner halo (seen on some of my photos).
4. 15% thin hexagonal plates with high angular dispersion around a horizontal axis ('Lowitz orientation parameters') ==> vertical pillars

Below are the results of our simulations, one in B&W showing the entire sky (white on black for clarity). The other attempts to recreate the apparent atmospheric view in colour, showing how it appears to the eye, rainbow features and all, showing that the diagonals and upper tangential arc were very faint and not readily visible:

The sun is blanked out in these simulates (it is at the centre of the inner halo) and therefore the flare of the sun on the camera lens obsucures most of the detail in the middle of this inner halo.

Another meteorological point is that the progression of these features throughout the afternoon indicated that populations of plates vs. prisms of ice changed proportions over time on the northwesterly breeze. Therefore settling, sorting, dispersal, tumbling, crystal growth all were very very dynamic during this afternoon. The sun pillar was more dominant towards the latter part of the evening.

An amazing feature of the Halosim program is that you can place any type of crystal in any colour of atmosphere with any type of sun...therefore allowing projections to be made from images from rovers on the moons of Jupiter and an assessment to be made about the crystals present in their atmospheres...sulphur...ice...or other!

The Graph of Graphs

All the >1 km diameter objects of the Solar System in a single image

Here I used data tables from Wikipedia of the diameter of the planets, moons from every planet, planetesimals and asteroids in relation to their orbit around either the sun or the particular planet. This way each object >1 km can be seen clearly on one graph but only if a log–log scale is used. The radius of the sun is plotted as an arbitrary bar at the top showing that it would potentially encroach into Earth's orbit if it were to become a red giant.

Some observations from this are:

• Mars has just two very small moons orbiting and very very low altitude
• Earth's Moon is very large given the size of the Earth and its position in the inner solar system
• From Jupiter to Neptune there is a logarithmic decay in planet size with orbital radius implying some degree of gravitational sorting of material in the early evolution of the solar nebula
• The moons of J, S, U and N follow a strikingly similar patterning on this graph with Jupiter having the most abundant spread due to it being well surveyed and containing many objects >1 km in diameter.
• These gas giants have moons that split into an inner ring of increasing size and outer ring of decreasing size, hence all the big moons are located at roughly 1M km radius.
• Three of these moons are larger than the smallest planet, Mercury. And many of these moons are larger than the largest planetesimals and dwarf planets in the outer reaches of the solar system.
• Pluto and Charon are clearly part of the dwarf planet/planetesimal cluster, hence their degradation from the planet category a decade ago.
• Scatter in the data beyond the orbit of Saturn indicates more observations are required.
• The Dwarf planets and asteroid belt show signs of interaction
• Oort Cloud and outer planetesimals show signs of interaction
• Due to its enormous surface area, the Oort Cloud probably represents a huge mass of material which is under-represented on this graph, especially considering objects <1 km in diameter.

Australia coverage

In WA we've really got to go to the Pilbara and Kimberley! Interstate TAS, NT need a bit of attention! [Woolfe Creek, Gosse Bluff and Mt Gambier are all on the wish list.]

Differences between N and S Hemisphere (compiled from various sources)

[text to be improved shortly]

Astronomical

• 4-5 days longer winter season due to elliptical orbit aphelion coincidence with NHsummer
• Hence, average day length is <minute longer
• Elliptical perihelion coincidence with SH summer
• Hence SH is 5 million kms closer to sun and receives 5% greater radiation
• SH can see magellanic clouds each night
• SH can see into galactic centre hence more and brighter stars with less light pollution
• NH better for deeps space observation (no galactic pollution)
• Can see Andromeda in NH closest neighbour galaxy
• SH an see Alpha Centuri closest star

Geological

• SH Cr-Ni-PGE-Au-Fe-U deposits >> population requires
• Oldest mineral SH
• Oldest rock NH

Geographical

• greater land area (and less sea area) in the NH (and probably more forests, agriculture, lakes etc.)
• ocean currents circle the earth at high latitudes in the SH but not in the NH
• polar regions of the SH are colder than the polar regions in the NH
• NH has land areas which are further from the oceans along the same line of latitude - i.e. east-west distance to the sea is greater.
• Presence of Antarctica in SH (= highest, driest, coldest, windiest continent)
• Antarctic ozone hole bigger
• UV penetration greater in SH therefore more genetic mutations
• Clockwise coriolis effect in SH

Biological

• SH Penguins
• NH Polar bears
• SH Greatest rainforest
• SH eucalyptus
• NH pine
• NH More vegetation

Human

• NH has a greater population and this means more large cities
• the use of energy (for heating, transport, power etc.) is greater in the NH and that means more "man-made" heat is released to the atmosphere
• carbon dioxide emissions in the NH are greater
• greater atmospheric pollution occurs in the NH
• Countries which are rapidly becoming industrialised - and increasing atmospheric emissions - such as China and India are located in the NH.

Music to listen to while studying different types of metamorphic rock

New year resolutions 2014

1. Less carb
2. More yoga
3. Be creative about cooking
4. Be creative about feng shui and orderliness
5. Be creative about travel/commuting
6. Be creative about entertainment
7. Increase the art and music
8. Philosophise a lot,
9. Think about big history thresholds (see Big History Project)

A list of discoveries from the last while

Discovery 1: The answer to a given question is undoubtedly somewhere in between all the extremes. This is self evident since extreme points of view or 'yes and no' answers summarise the knowledge of the universe that is present in the minds of humans. Therefore, if we are able to summarise available knowledge and perspectives and take it all into account (a difficult thing to do as an individual), we will end up with the most wholesome answer...the closest thing possible to a universal truth from a human perspective at least. This is also a way to avoid ignorance and to be inclusive.

Discovery 2: Be creative about all things. The big and the small are both extremely important since big and complex things (such as high-level research) emerge from the simplest of experiences. For example: orderliness around a home (such as washing the dishes or arranging the garden) has huge effects on our mode of life and way of being. Patience and enjoyment of 'menial' tasks means that we can never be bored and can never have the feeling of meaninglessness in our lives.

Discovery 3: The mind can make trillions of connections that are as expansive as the universe. Therefore, in this, there is endless possibility. Don't accept limitation.

Discovery 4: In every difficulty lies opportunity. (This is evident from number 3 since difficulty presents us with real problems and demands creative solutions).

Discovery 5: Sharing ideas just has to be a good thing! I can't accept the idea that keeping discoveries and ideas to ourselves (this is rife in the academic world) serves any great purpose.