APOD: Swiss Alps, Martian Sky (2021 Feb 18)

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APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by APOD Robot » Thu Feb 18, 2021 5:07 am

Image Swiss Alps, Martian Sky

Explanation: Taken on February 6, this snowy mountain and skyscape was captured near Melchsee-Frutt, central Switzerland, planet Earth. The reddish daylight and blue tinted glow around the afternoon Sun are colors of the Martian sky, though. Of course both worlds have the same Sun. From Mars, the Sun looks only about half as bright and 2/3 the size compared to its appearance from Earth. Lofted from the surface of Mars, fine dust particles suspended in the thin Martian atmosphere are rich in the iron oxides that make the Red Planet red. They tend to absorb blue sunlight giving a red tinge to the Martian sky, while forward scattering still makes the light appear relatively bluish near the smaller, fainter Martian Sun. Normally Earth's denser atmosphere strongly scatters blue light, making the terrestrial sky blue. But on February 6 a huge cloud of dust blown across the Mediterranean from the Sahara desert reached the Swiss Alps, dimming the Sun and lending that Alpine afternoon the colors of the Martian sky. By the next day, only the snow was left covered with reddish dust.

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by Ann » Thu Feb 18, 2021 5:49 am

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by orin stepanek » Thu Feb 18, 2021 1:53 pm

Swiss Alps or Mars? Telephone poles give it away! 8-) Does indeed look like a scene from Mars! :mrgreen:
Orin

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by E Fish » Thu Feb 18, 2021 2:11 pm

orin stepanek wrote:
Thu Feb 18, 2021 1:53 pm
Swiss Alps or Mars? Telephone poles give it away! 8-) Does indeed look like a scene from Mars! :mrgreen:
Didn't you know that Mars has a strong communications infrastructure? :D

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by johnnydeep » Thu Feb 18, 2021 3:27 pm

APOD Robot wrote:
Thu Feb 18, 2021 5:07 am
Image Swiss Alps, Martian Sky

Explanation: Taken on February 6, this snowy mountain and skyscape was captured near Melchsee-Frutt, central Switzerland, planet Earth. The reddish daylight and blue tinted glow around the afternoon Sun are colors of the Martian sky, though. Of course both worlds have the same Sun. From Mars, the Sun looks only about half as bright and 2/3 the size compared to its appearance from Earth. Lofted from the surface of Mars, fine dust particles suspended in the thin Martian atmosphere are rich in the iron oxides that make the Red Planet red. They tend to absorb blue sunlight giving a red tinge to the Martian sky, while forward scattering still makes the light appear relatively bluish near the smaller, fainter Martian Sun. Normally Earth's denser atmosphere strongly scatters blue light, making the terrestrial sky blue. But on February 6 a huge cloud of dust blown across the Mediterranean from the Sahara desert reached the Swiss Alps, dimming the Sun and lending that Alpine afternoon the colors of the Martian sky. By the next day, only the snow was left covered with reddish dust.
Psyche! I was tricked I tell you! I thought first that this was a composite of an actual Martian sky, taken perhaps from some rover, combined with the more mundane, yet magnificent, Earthly Alps. That is, until I read further... :ssmile:
"To Boldly Go......Beyond The Fields We Know."

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by Tilt » Thu Feb 18, 2021 4:51 pm

I forget where i stole this...

""The old song goes: "Tell me why the stars do shine. Tell me why the ivy twines. Tell me why the skies are blue. And I will tell you why I love you."

In response, an irreverent college student wrote: "Nuclear fusion makes stars to shine. Tropisms cause the ivy to twine. Rayleigh scattering makes skies so blue. And glandular hormones are why I love you."
""
Or was it previously lifted from Isaac Asimov?

WWW

Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by WWW » Thu Feb 18, 2021 11:11 pm

Congratulations to NASA/JPL and the Mars 2020 Perseverance team on another successful Mars landing.

https://mars.nasa.gov/news/8865/touchdo ... ed-planet/

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by johnnydeep » Fri Feb 19, 2021 12:16 am

WWW wrote:
Thu Feb 18, 2021 11:11 pm
Congratulations to NASA/JPL and the Mars 2020 Perseverance team on another successful Mars landing.

https://mars.nasa.gov/news/8865/touchdo ... ed-planet/
Indeed! I’m super stoked. I heard that NASA is 5 for 5 in landing rovers on Mars!
"To Boldly Go......Beyond The Fields We Know."

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by Chris Peterson » Fri Feb 19, 2021 12:44 am

johnnydeep wrote:
Fri Feb 19, 2021 12:16 am
WWW wrote:
Thu Feb 18, 2021 11:11 pm
Congratulations to NASA/JPL and the Mars 2020 Perseverance team on another successful Mars landing.

https://mars.nasa.gov/news/8865/touchdo ... ed-planet/
Indeed! I’m super stoked. I heard that NASA is 5 for 5 in landing rovers on Mars!
I was lucky enough to be working at JPL with image data (working from mag tape!) during the Viking 1 mission. What an amazing road it's been!
Chris

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by Chemfarmer » Fri Feb 19, 2021 3:12 am

The caption said that the sun is about 2/3 the size from mars as it is from earth. But I was under the impression that the apparent size of an object dropped off as the square of the distance away. So doing the math, with mars 141 million miles and earth at 93 million miles: (93 x 93)/(141 x 141), I get that the sun should be about 44% as large from mars as from earth. Please confirm or correct. Thanks.

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Re: APOD: Swiss Alps, Martian Sky (2021 Feb 18)

Post by Chris Peterson » Fri Feb 19, 2021 3:37 am

Chemfarmer wrote:
Fri Feb 19, 2021 3:12 am
The caption said that the sun is about 2/3 the size from mars as it is from earth. But I was under the impression that the apparent size of an object dropped off as the square of the distance away. So doing the math, with mars 141 million miles and earth at 93 million miles: (93 x 93)/(141 x 141), I get that the sun should be about 44% as large from mars as from earth. Please confirm or correct. Thanks.
The diameter is proportional to the inverse of distance. Twice as far away, half the diameter.

Both the area and the brightness are proportional to the inverse square of the distance.
Chris

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