Mars White Albedo Feature

[Nightspore]

I was going to go out Saturday night for a rich field session with the 72 ED DS Pro, unfortunately rain stopped play.  My new weather app ‘Yo Weather’ (honestly) said it would clear around 03:20 to 04:00. By 03:30 I was set-up and looking up at cloudy sky porridge except for a brief naked eye view of Mars. Then, around 04:25 it started to clear and I could see Mars approaching transit. The 72 ED had been set-up with the 5x Tele Vue Powermate and a 10mm Vixen NPL most of this time just sitting there in case Mars reappeared. I got a sharp, clear 210x, and could easily see the phase. 

 

 

Mars was 89.9% illuminated, 17.6 arc seconds in diameter and -1.6 visual magnitude. There was a Baader Semi APO in the diagonal nosepiece in case I wanted to swap eyepieces more easily. The southern polar cap was visible and a lot of albedo features. I recognised the Syrtis Major Planum, although I was expecting to see it. What appeared to be clouds were in the northern polar region again as well. I actually did swap eyepieces, but to a 10mm Baader Eudiascopic as I thought it might give more contrast as daylight approached. It has around a 43 degree FOV but I could keep Mars in field at 210x with some effort with the alt-az. I observed Mars until an hour after transit. I was really impressed. Later I caught a rising Venus and saw Orion rise with the naked eye.

 

 

The picture above is an approximation of the white spot I saw (the actual image was much smaller of course). The odds are this is just cloud, I've been seeing it for a while, with different scopes, eyepieces and diagonals. On Sunday I actually started off with a Baader Amici prism and switched to a Baader T2 prism. The simulation above (SN8/Photoshop) is mirror reversed. I'm pretty convinced this isn't being caused by anything in my optical train.

 

 

I'm wondering if I'm seeing a bright white albedo feature rather than clouds. I did some research and this might be one or more of the lobate debris aprons (LDA's) like in the Promethei Terra region. These may even be glaciers or ice/snow deposits not dissimilar to the ice sheet in Oxus Patera (Arabia Terra).

 

(Nasa)

 

 

[Guest]

Did you get any of these images with your ED72?

[Nightspore]

4 hours ago, Sunny Phil said:

Did you get any of these images with your ED72?

No, they're all screenshots from various software. The second picture, which is mirror-reversed, is from SN8 and I added the white albedo feature with Photoshop. The last picture is from Nasa and public domain. I've observed Mars since with the 72ED at 190x and 210x with Baader Neodymium and Semi APO filters. The transparency wasn't good and Mars was much lower. The southern pole looks a bit yellow even without a filter.  The white albedo feature in the north was still there. Others have also seen it.

[Guest]

I need to get my Mak on it. Apart from the weather, I also have a pain in my hip that makes carrying telescopes difficult.

[Nightspore]

I want to set my EQ5 up soon, I usually leave it at the northern end of my garden covered with a tarpaulin. In this way I only have to carry the 150mm Newtonian OTA out to it when I want an observing session.

 

 

I'm partially paralysed on the entire right side of my body, so my smaller scopes get out more often lol. I've seen small white albedo features on Mars in previous opposition years, but this is big enough to see with a 72mm refractor.  I've seen it with my 80ED DS Pro and my 102mm ED doublet. I automatically assumed it was cloud. 

 

 

I'm leaning towards the idea of sunlight reflecting off a large flat plain of some description.

 

 

Maybe not unlike something similar to the Indus Vallis area. The southern pole is easily visible this opposition year. In years past I've often struggled to see either pole and occasionally needed filters. The angle of sunlight must be making the pole more visible, and doing the same for the white albedo feature.

Edited August 29, 2020 by Nightspore
Gremlins

[Nightspore]

After some research I'm fairly certain that the white 'cloud' feature I've been regularly observing on Mars is a manifestation of the Northern Polar Hood.

 

"The ice cap in the north is of a lower altitude (base at -5000 m, top at -2000 m) than the one in the south (base at 1000 m, top at 3500 m).[21][22] It is also warmer, so all the frozen carbon dioxide disappears each summer.[23] The part of the cap that survives the summer is called the north residual cap and is made of water ice. This water ice is believed to be as much as three kilometres thick. The much thinner seasonal cap starts to form in the late summer to early fall when a variety of clouds form. Called the polar hood, the clouds drop precipitation which thickens the cap." ~ Wikipedia

 

The image below is a screenshot from Stellarium, edited, mirror reversed, and re-oriented in the Glimpse Image Editor.

 

 

Although much bigger and more defined than I've been seeing through the eyepiece (for clarity), this is an approximation to what I saw on 19/9/20 roughly at transit. I've tinted the southern pole with yellow as it appears this way to me (even unfiltered) and I've added an approximation of the Northern Polar Hood.

 

Edited September 20, 2020 by Nightspore
Gremlins with attitude