APOD: Mercury as Revealed by MESSENGER (2017 Jul 23)

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APOD: Mercury as Revealed by MESSENGER (2017 Jul 23)

Post by APOD Robot » Sun Jul 23, 2017 4:10 am

Image Mercury as Revealed by MESSENGER

Explanation: Mercury had never been seen like this before. In 2008, the robotic MESSENGER spacecraft buzzed past Mercury for the second time and imaged terrain mapped previously only by comparatively crude radar. The featured image was recorded as MESSENGER looked back 90 minutes after passing, from an altitude of about 27,000 kilometers. Visible in the image, among many other newly imaged features, are unusually long rays that appear to run like meridians of longitude out from a young crater near the northern limb. MESSENGER entered orbit around Mercury in 2011 and finished its primary mission in 2012, but took detailed measurements until 2015, at which time it ran out of fuel and so was instructed to impact Mercury's surface.

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Re: APOD: Mercury as Revealed by MESSENGER (2017 Jul 23)

Post by ta152h0 » Sun Jul 23, 2017 8:25 am

I have a few mercury dimes, that my descendants will surely fight over
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Re: APOD: Mercury as Revealed by MESSENGER (2017 Jul 23)

Post by heehaw » Sun Jul 23, 2017 9:57 am

When I was a boy, we were told that Mercury's rotation period was the same as its period of revolution, so the same side of Mercury always faced the Sun. Now we know that one day on Mercury is two years long.

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Re: APOD: Mercury as Revealed by MESSENGER (2017 Jul 23)

Post by De58te » Sun Jul 23, 2017 10:50 am

heehaw wrote: Now we know that one day on Mercury is two years long.
Has there been new statistics about Mercury? I thought Mercury's day was 59 Earth days long and a Mercury year was 88 Earth days. In other words there is a sunrise on a given spot on Mercury about every two Earth months, and there are 1 and a half Mercury days in a Mercury year.

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Re: APOD: Mercury as Revealed by MESSENGER (2017 Jul 23)

Post by neufer » Sun Jul 23, 2017 11:46 am

De58te wrote:
heehaw wrote:

Now we know that one day on Mercury is two years long.
Has there been new statistics about Mercury? I thought Mercury's day was 59 Earth days long and a Mercury year was 88 Earth days. In other words there is a sunrise on a given spot on Mercury about every two Earth months, and there are 1 and a half Mercury days in a Mercury year.
You are both right in a sense.

After one (87.97 day long) Mercury year
Mercury has spun 3/2 times (sidereal rotation period = 58.646 days).
However that amounts to only 1/2 a rotation vs-a-vis the Sun itself.

A full solar day requires two Mercury years and three full rotations.
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Re: APOD: Mercury as Revealed by MESSENGER (2017 Jul 23)

Post by neufer » Sun Jul 23, 2017 1:58 pm

ta152h0 wrote:
I have a few mercury dimes, that my descendants will surely fight over
https://en.wikipedia.org/wiki/Mercury_dime wrote:

<<The Mercury dime is a ten-cent coin struck by the United States Mint from 1916 to 1945. Designed by Adolph Weinman and more correctly referred to as the Winged Liberty Head dime, it gained its common name as the obverse depiction of a young Liberty, identifiable by her winged Phrygian cap, was confused with the Roman god Mercury: This misattribution appeared almost immediately in the popular press, as writers imagined that the obviously female Liberty was actually a representation of Mercury, messenger to the Roman gods of mythology and quite certainly a male. It is popularly known as the Mercury Dime even today, despite noble but ill-fated attempts by some publications to reverse this error.

The dime was struck in substantial numbers until 1930, with the notable exception of the 1916-D issue and from 1921 to 1923, when an economic downturn caused the need for coins to diminish. No dimes were struck for 1922, the first time since 1826 that this had occurred. With the onset of the Great Depression, mintages dropped again in 1930 and 1931; coinage of dimes was suspended entirely in 1932 and 1933. The low-mintage dates are not rare today as many were hoarded, and 1930- and 1931-dated dimes proved readily available from the banks once the economy improved. With the economy beginning to pick up again, coinage resumed in 1934, and the dime was struck in large numbers each year through the end of the series.

The death of President Franklin Roosevelt in April 1945 brought immediate calls for a coin to be issued with his image. As Roosevelt had been closely associated with the March of Dimes, and as the dime's design could be replaced without the need for congressional action as it had been struck for more than 25 years, the Treasury chose that denomination to honor Roosevelt. Mint Chief Engraver John R. Sinnock, Morgan's successor, executed the design featuring Roosevelt, which replaced the Mercury dime in 1946, making 1945 the last year in which it was produced. According to Mint Director Nellie Tayloe Ross, a total of 2,677,232,488 Mercury dimes were struck.>>
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Re: APOD: Mercury as Revealed by MESSENGER (2017 Jul 23)

Post by Boomer12k » Mon Jul 24, 2017 1:21 am

A moon without a planet.... :oops:

Sorry....

My Mercury from 2012. If you click and enlarge, you can see it is in a phase. If not for my LX200 GPS scope, I would not have found it. This was actually the first time I had seen it. I had been trying visually for years. Took a GOTO scope....
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