APOD: All of Mercury (2019 Apr 28)

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APOD Robot
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APOD: All of Mercury (2019 Apr 28)

Post by APOD Robot » Sun Apr 28, 2019 4:07 am

Image All of Mercury

Explanation: Only six years ago, the entire surface of planet Mercury was finally mapped. Detailed observations of the innermost planet's surprising crust began when the robotic have been ongoing since the robotic MESSENGER spacecraft first passed Mercury in 2008 and continued until its controlled crash landing in 2015. Previously, much of the Mercury's surface was unknown as it is too far for Earth-bound telescopes to see clearly, while the Mariner 10 flybys in the 1970s observed only about half. The featured video is a compilation of thousands of images of Mercury rendered in exaggerated colors to better contrast different surface features. Visible on the rotating world are rays emanating from a northern impact that stretch across much of the planet, while about half-way through the video the light colored Caloris Basin rotates into view, a northern ancient impact feature that filled with lava. Recent analysis of MESSENGER data indicates that Mercury has a solid inner core.

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Boomer12k
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Re: APOD: All of Mercury (2019 Apr 28)

Post by Boomer12k » Sun Apr 28, 2019 7:54 am

Awesome...looks like no place has been left unscathed...

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Re: APOD: All of Mercury (2019 Apr 28)

Post by orin stepanek » Sun Apr 28, 2019 11:26 am

Nice video! :D
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Re: APOD: All of Mercury (2019 Apr 28)

Post by BDanielMayfield » Sun Apr 28, 2019 12:40 pm

Why does such a small planet have such a large core? Three ideas are in play:
Mercury's core has a higher iron content than that of any other major planet in the Solar System, and several theories have been proposed to explain this. The most widely accepted theory is that Mercury originally had a metal–silicate ratio similar to common chondrite meteorites, thought to be typical of the Solar System's rocky matter, and a mass approximately 2.25 times its current mass.[32] Early in the Solar System's history, Mercury may have been struck by a planetesimal of approximately 1/6 that mass and several thousand kilometers across.[32] The impact would have stripped away much of the original crust and mantle, leaving the core behind as a relatively major component.[32] A similar process, known as the giant impact hypothesis, has been proposed to explain the formation of the Moon.[32]

Alternatively, Mercury may have formed from the solar nebula before the Sun's energy output had stabilized. It would initially have had twice its present mass, but as the protosun contracted, temperatures near Mercury could have been between 2,500 and 3,500 K and possibly even as high as 10,000 K.[33] Much of Mercury's surface rock could have been vaporized at such temperatures, forming an atmosphere of "rock vapor" that could have been carried away by the solar wind.[33]

A third hypothesis proposes that the solar nebula caused drag on the particles from which Mercury was accreting, which meant that lighter particles were lost from the accreting material and not gathered by Mercury.[34] Each hypothesis predicts a different surface composition, and there are two space missions set to make observations. MESSENGER, which ended in 2015, found higher-than-expected potassium and sulfur levels on the surface, suggesting that the giant impact hypothesis and vaporization of the crust and mantle did not occur because potassium and sulfur would have been driven off by the extreme heat of these events.[35] BepiColombo, which will arrive at Mercury in 2025, will make observations to test these hypotheses.[36] The findings so far would seem to favor the third hypothesis; however, further analysis of the data is needed.[37]
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Re: APOD: All of Mercury (2019 Apr 28)

Post by neufer » Sun Apr 28, 2019 12:57 pm

https://en.wikipedia.org/wiki/Mercury_(planet)#Ground-based_telescopic_research wrote:

<<The difficulties inherent in observing Mercury mean that it has been far less studied than the other planets. In 1800, Johann Schröter made observations of surface features, claiming to have observed 20-kilometre-high (12 mi) mountains. Friedrich Bessel used Schröter's drawings to erroneously estimate the rotation period as 24 hours and an axial tilt of 70°. In the 1880s, Giovanni Schiaparelli mapped the planet more accurately, and suggested that Mercury's rotational period was 88 days, the same as its orbital period due to tidal locking. This phenomenon is known as synchronous rotation. The effort to map the surface of Mercury was continued by Eugenios Antoniadi, who published a book in 1934 that included both maps and his own observations. Many of the planet's surface features, particularly the albedo features, take their names from Antoniadi's map.>>
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