32 replies to this topic

[Grounddweller]

Hello all,

Last night I had first light with a 16" Skywatcher SkyScan that I had acquired and replaced the mirrors in ( Thank you Nick in MN for them! ). Mostly cloudy and our public star party was cancelled as a result, so I was bummed not to be able to use the 16. Then, letting the dog out some hours later, I saw that the clouds had broke for a time and I decided to try and get the beast out in the driveway to test the optics. Not a lot of time to waste, the tracking was easy to set and accurate (Yay!) I viewed Jupiter, M42 ( magnificent, E & F stars -widely- separated and the nebula was pronounced) and Mars. The seeing was not optimal with higher humidity, but I do have Bortles 4 skies right above the house. At first blush I thought I had an issue with the eyepiece, as the one side of Mars was highly illuminated, almost looking like a profile of an eyeball. Then I realized it must be the polar cap!!! (Duh...) I was mesmerized by the view and stayed on it for the duration of the clear sky break I had. Now I realize that this being my first view of Mars at such a high magnification (450-600x) the cap would possibly seem larger than life. Mars itself was bigger than I had ever viewed it, and the detail on the surface was rather striking. My question concerns the expanse of the cap. Is it always this size? Is it larger at this point than it has been, and does it vary consequently? It was certainly an image that will stay with me for some time (and BTW, I am extremely chuffed with the SW 16")

[Justin Fuller]

Good observation! Mars is coming out of its northern hemisphere Spring and going into its Summer (so the northern polar cap hasn't spent all of summer and autumn sublimating yet), and the northern hemisphere is pointed toward us. The permanent northern polar cap is also larger than the permanent southern polar cap.  How prominent the poles appear depends on the Martian season and our viewing angle toward whatever pole is experiencing/ has experienced Winter most recently. An autumn southern hemisphere view of mars, especially if it's not angled toward us can look non-existent. There are also polar clouds (often called a polar hood) that can form above high latitudes and enhance the whiteness of the pole. Compared to the last 10 years or so of other Mars oppositions this is one of the more prominent polar caps visible because of the conditions above.

Edited by Justin Fuller, 02 February 2025 - 10:54 AM.

[Blast_off]

Why isn't mars surface cratered like the moon?

[deSitter]

It's very cold there because Mars is near aphelion in its orbit, which is much farther away than perihelion.

 

-drl

[Grounddweller]

Blast_off, on 02 Feb 2025 - 10:28 AM, said:
Why isn't mars surface cratered like the moon?

 

Mars does/did have an atmosphere of consequence, so it has been able to be protected somewhat from wayward impacts. Plus, Mars had some tectonic activity at some point so impact locations could be morphed by the activity. In contrast the moon is without a protective atmosphere and has a locked crust with no ability to smooth over the impact locations.

Edited by Grounddweller, 02 February 2025 - 11:39 AM.

[Inkie]

Atmospheric influences over time, not recently of course, but early when it, as well as the Earth, were routinely bombarded with 'stuff'.  Over 300M years that followed, there was enough of an atmosphere to cause considerable 'smoothing', just as it has done on Earth (for about 15 times as long).  And, yes, tectonics, although as a much smaller planet, it has less of that effect than goes on constantly on good old Earth.  Mars' morphology at the surface is thought to be more due to convective cooling and shrinking as the heat at the core is bled off.

[areyoukiddingme]

I don't know how the extent of the ice cap compares to other years (seems about normal to me).

 

There is an optical illusion where we perceive brighter stuff as bigger, so I wonder if some of that might be adding to the effect.

 

Here's an image from Sky and Telescope that shows it for the moon. I would suspect something more subtle for Mars ice caps.

 

[quilty]

In order to get this straight:

Now the icecap I see on top of Mars is the largest I've seen yet. That top cap is it North or South?

Why less craters than on the moon?

I can tell two reasons:
1. I wouldn't resolve them with my scopes
2. The atmosphere might blow apart most of the sharp structures
3....maybe more

[Sebastian_Sajaroff]

Yes, the ice cap is prominent these weeks.
It’s obvious on my 3" at 100x, that says something !
During the 2018 and 2020 oppositions, I could barely see it on my 6", but not on the 3"

[Dave Mitsky]

Why isn't mars surface cratered like the moon?

Mars does indeed have some craters.

 

https://en.wikipedia...craters_on_Mars

https://earthsky.org...omars-may-2024/

https://images.newsc...4.jpg?width=837

 

https://www.planetar...craters-on-mars

[deSitter]

Mars does indeed have some craters.

 

https://en.wikipedia...craters_on_Mars

https://earthsky.org...omars-may-2024/

https://images.newsc...4.jpg?width=837

 

https://www.planetar...craters-on-mars

It has a LOT of them, and their discovery dismayed those hoping to find life on Mars. The clear images from Mariner 4, the first flyby of Mars, showed them. They proved that the wispy atmosphere of Mars was a very long termed phenomenon.

 

Image credit NASA.

 

-drl

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[Dave Mitsky]

It has a LOT of them, and their discovery dismayed those hoping to find life on Mars. The clear images from Mariner 4, the first flyby of Mars, showed them. They proved that the wispy atmosphere of Mars was a very long termed phenomenon.

 

Image credit NASA.

 

-drl

Well, that was fairly obvious from the first link in my reply.

 

As of 2017, Martian craters account for 21% of all 5,211 named craters in the Solar System. Apart from the Moon, no other body has as many named craters as Mars.

https://en.wikipedia...craters_on_Mars

[quilty]

Is the icecap N or S?

[Grounddweller]

I believe this was the northern cap.

[quilty]

Me too, but last time it seems I was wrong

[Blast_off]

Thank all of you who replied, one more question.........Why are some of  the craters on the moon so perfectly round as if straight vertical  impact with no eject dump outside the crater?  Thanks again.

[quilty]

yes, never seen a comatic crater on the moon yet. Look like frozen waves either in the solid or just dust.
The only traces of skimming seem to be those catenae. Tells both about the consistency of the meteorites as well as the moon's surface.
I think both must be very brittle. Which is most likely to be the case for stone, dust and ice
There's more to observe, for instance the crater distribution on the moon and their ages

Edited by quilty, 13 February 2025 - 06:39 PM.

[Dave Mitsky]

Is the icecap N or S?

The northern ice cap is facing the Earth during this apparition.

 

The most prominent and enticing feature visible right now is the North Polar Cap. During our early fall season it was hidden beneath the clouds of the North Polar Hood, but when northern Martian spring began in earnest in late November they parted to reveal a gleaming lentil-like cap of carbon dioxide ice visible even at 50x. As spring deepens into summer, the Sun will gradually warm and vaporize the ice, eventually exposing the much smaller, residual water-ice cap. Regular observers of the planet can watch it shrink right before their eyes. Mars contracts and fades faster than you think. One month past opposition on Feb. 16th, it dips to magnitude –0.6 and contracts to 12.1″. Observe it as often as you can.

https://skyandtelesc...olled-into-one/

[quilty]

Thanks. But why is it displayed South in your link? it's displayed bottom while with all my scopes I find it top on Mars? The scope swaps W and E but not N with S

Martian icecap melting and vaproising due to climate change. How can we help it? Cover with white blankets like they do in Austria? :-)

Edited by quilty, 15 February 2025 - 04:32 AM.

[Dave Mitsky]

Thanks. But why is it displayed South in your link? it's displayed bottom while with all my scopes I find it top on Mars? The scope swaps W and E but not N with S

Martian icecap melting and vaproising due to climate change. How can we help it? Cover with white blankets like they do in Austria? :-)

I made this sketch with Photoshop through my 10-inch f/6 Dob with a magnification of 317x on Jan. 3rd around 11:00 UT. The North Polar Cap couldn't be missed! The other markings were obvious except for the Trivium Charontis, which required continued observation to ascertain its shape and extent. South is up in all close-up images.
Bob King

A telescope producing two reflections "inverts" images.

Newtonian reflector telescopes were also designed for astronomical use and images of terrestrial objects will appear upside-down. Because the design uses two mirrors, the images you see are correct left to right and up and down, but the views are rotated, depending on the angle of the focuser and the ground as well as how you hold your head to the eyepiece. Using a diagonal like the refractor would actually cause more problems by mirror reversing the image and not really correcting the image at all. Unfortunately for Newtonian telescopes, there is no easy way to correct this.
 

Astronomers don’t mind an upside-down view since there is really no up or down in space. It is all a matter of perspective. Because the Earth we live on is roughly shaped like a sphere, a person in Australia looking at the Moon with the naked eye would see it upside-down compared to a person simultaneously observing it from Alaska. They are looking at the same object, but from different perspectives.

 

https://www.celestro...g-wrong-with-it

Sky & Telescope's Mars Profiler gives the options of a direct view, an inverted view, and a mirror reversed view of Mars.

https://skyandtelesc...ide-is-visible/

[Epick Crom]

Yes I agree, Mars polar cap is very prominent this apparition.  This is my third Mars apparition since becoming an observer in 2019 and the polar cap is the biggest and brightest I've ever seen it.

 

 

Clear Skies 

Joe

[quilty]

Me, too, it is. But it's on top of Mars and not on its buttom. When my ep is directed above, That's a no brainer that I don't rotate the ep when doing such statements.
Once again: How come that the my icecap is on top through the Mak while yours Newtonian one is at the bottom?

So maybe the icecap is not just larger but norther :-) as well as typical?

Stellarium displays the cap at 1 o clock, too

So, what's wromg in general?

When we observe Mars, the moon Jupe or Sat in the southern Sky, in their highest elevation that night through a dob or frac, ep directed straight upwards (with respect to the tube)
Where is North then, on top or buttom?

Edited by quilty, 16 February 2025 - 03:36 AM.

[Grounddweller]

Me, too, it is. But it's on top of Mars and not on its buttom. When my ep is directed above, That's a no brainer that I don't rotate the ep when doing such statements.
Once again: How come that the my icecap is on top through the Mak while yours Newtonian one is at the bottom?

So maybe the icecap is not just larger but norther :-) as well as typical?

Stellarium displays the cap at 1 o clock, too

So, what's wromg in general?

When we observe Mars, the moon Jupe or Sat in the southern Sky, in their highest elevation that night through a dob or frac, ep directed straight upwards (with respect to the tube)
Where is North then, on top or buttom?

I believe it is dependent on the orientation of the view angle, whether it is on the left or right side of the tube. If the object ( in this case, a planet ) is coming through as an image to the eyepiece it will appear differently on one side of the tube as opposed to the other side.

Edited by Grounddweller, 16 February 2025 - 09:12 AM.

[Dave Mitsky]

The following Stellarium screen shots show Mars at 8:00 p.m. EST and 12:00 a.m. EST tonight from 40 degrees north.  Notice the change in the position of the NPC caused by the change in position of Mars in the sky and by the rotation of the planet.  These are direct views.

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[quilty]

Stellarium at my site isn't always correct. At 10 pm the moon constellation at Jupe was correct but the GRS was on the wrong side.
Just checked again. EP straight up, Mars South at 10 pm and the icecap at 12:30 (on top) CET.

Seems to be the 270° position in this row:



with the icecap on the other pole