APOD: Mercury from Passing BepiColombo (2022 Jun 28)

APOD Robot · Post by **APOD Robot** » Tue Jun 28, 2022 4:05 am

Mercury from Passing BepiColombo

Explanation: Which part of the Moon is this? No part -- because this is the planet Mercury. Mercury's old surface is heavily cratered like that of Earth's Moon. Mercury, while only slightly larger than Luna, is much denser and more massive than any Solar System moon because it is made mostly of iron. In fact, our Earth is the only planet more dense. Because Mercury rotates exactly three times for every two orbits around the Sun, and because Mercury's orbit is so elliptical, visitors on Mercury could see the Sun rise, stop in the sky, go back toward the rising horizon, stop again, and then set quickly over the other horizon. From Earth, Mercury's proximity to the Sun causes it to be visible only for a short time just after sunset or just before sunrise. The featured image was captured last week by ESA and JAXA's passing BepiColombo spacecraft as it sheds energy and prepares to orbit the innermost planet starting in 2025.

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Ann · Post by **Ann** » Tue Jun 28, 2022 4:23 am

The Moon is one of a dozen, Mercury is a little bit different but the Earth is one of a kind.

APOD Robot wrote:
In fact, our Earth is the only planet more dense.

This is yet another thing that sets the Earth apart. I guess that our planet's density was caused by the collision between proto-Earth and Theia. A large iron core would certainly have helped keeping the Earth's climate stable over billions of years. When the solar system was young and the Sun was fainter, the Earth's core would have generated more heat than today through radioactive decay and kept the early life forms on our fair planet cosy and snug.

Thank you, Earth. And thank you, Universe, for rolling dice a billion times - no, make that a billion multiplied by a billion multiplied by... Anyway, thank you, Universe, for coming up with the Earth!

Ann

XgeoX · Post by **XgeoX** » Tue Jun 28, 2022 5:48 am

Earth might be the densest planet but the reason Earth is more dense is because of gravitational compression. In fact though Mercury is by far the smallest planet with a radius of 2440 km it has basically the same surface gravity of Mars which has a radius of 3396 km!
Awesome photo btw. I love when you can see the spacecraft and the planet together like that. It’s a shame that Europe cheaped out and cancelled the lander, I was really looking forward to that.

Chris Peterson · Post by **Chris Peterson** » Tue Jun 28, 2022 12:33 pm

Ann wrote: ↑Tue Jun 28, 2022 4:23 am The Moon is one of a dozen, Mercury is a little bit different but the Earth is one of a kind.

APOD Robot wrote:
In fact, our Earth is the only planet more dense.
This is yet another thing that sets the Earth apart. I guess that our planet's density was caused by the collision between proto-Earth and Theia. A large iron core would certainly have helped keeping the Earth's climate stable over billions of years. When the solar system was young and the Sun was fainter, the Earth's core would have generated more heat than today through radioactive decay and kept the early life forms on our fair planet cosy and snug.

Thank you, Earth. And thank you, Universe, for rolling dice a billion times - no, make that a billion multiplied by a billion multiplied by... Anyway, thank you, Universe, for coming up with the Earth!

Ann

I don't think the formation of the Moon had much to do with Earth's density. More likely this is simply the density we'd expect for a terrestrial planet the size of our planet. Venus has about the same density as the Earth (just 5% less).

orin stepanek · Post by **orin stepanek** » Tue Jun 28, 2022 1:11 pm

The saying; Nice place to visit but wouldn't wouldn't want to live
there! Eh; wouldn't want to visit there either! Well maybe through a
telescope!

Dogs look dumbfounded!

Fred the Cat · Post by **Fred the Cat** » Tue Jun 28, 2022 1:28 pm

XgeoX wrote: ↑Tue Jun 28, 2022 5:48 am Earth might be the densest planet but the reason Earth is more dense is because of gravitational compression. In fact though Mercury is by far the smallest planet with a radius of 2440 km it has basically the same surface gravity of Mars which has a radius of 3396 km!
Awesome photo btw. I love when you can see the spacecraft and the planet together like that. It’s a shame that Europe cheaped out and cancelled the lander, I was really looking forward to that.

You would think a lander might have been more than a dream and a book.

Starship Asterisk*

APOD: Mercury from Passing BepiColombo (2022 Jun 28)

APOD: Mercury from Passing BepiColombo (2022 Jun 28)

Re: APOD: Mercury from Passing BepiColombo (2022 Jun 28)

Re: APOD: Mercury from Passing BepiColombo (2022 Jun 28)

Re: APOD: Mercury from Passing BepiColombo (2022 Jun 28)

Re: APOD: Mercury from Passing BepiColombo (2022 Jun 28)

Re: APOD: Mercury from Passing BepiColombo (2022 Jun 28)