Starship Asterisk*

[attachment=0]Dawn-in-Clavius-Tycho-07-07-22_1024.jpg[/attachment]Interesting that the young and old are so close! :shock:

I'm always amazed how much the Moon looksJUST like Mercury! Or vv. It tells us that, throughout the universe, there are QUINTILLIONS UPON QUINTILLIONS of almost identical bodies. It is the most cosmically boring thing imaginable! And it's our universe! Thank heaven for the rings of Saturn?

[quote=Tekija post_id=324334 time=1658000944]
Clavius´floor encompases an artistic arc of six smaller craters of progressively diminishing size, two of which are highlighted in today´s image by the sun.

[url]https://apod.nasa.gov/apod/ap200206.html[/url]
[/quote]

Yup. Not sure if all these craters were created by the same impact even or not, but it seems unlikely - I would expect any impactor breakups or skips to result in a line of craters (like the little line of three just above the arc), not an arc:


[attachment=0]clavius crater arc.JPG[/attachment]


[ EDIT: but perhaps an arc [b][i]could[/i][/b] result if the impactor was rotating sufficiently? ]

Clavius´floor encompases an artistic arc of six smaller craters of progressively diminishing size, two of which are highlighted in today´s image by the sun.

[url]https://apod.nasa.gov/apod/ap200206.html[/url]

[quote=bystander post_id=324327 time=1657990438 user_id=112005]
[quote=xdm post_id=324319 time=1657965738]
...
Why present a mirror image, by the way :?:
[/quote]
The image may be inverted by the telescope.
You might need to invert the data to correct it.
[/quote]

The most common cause of mirror reversal is the use of a [url=https://en.wikipedia.org/wiki/Star_diagonal]star diagonal[/url]. These are commonly used for observing convenience, although less commonly used for imaging. When they are used for imaging, one typically reverses the image in processing so that the correct image is presented, thus preserving the relationships of cardinal directions and avoiding confusion.

[quote=xdm post_id=324319 time=1657965738]
...
Why present a mirror image, by the way :?:
[/quote]
The image may be inverted by the telescope.
You might need to invert the data to correct it.

[quote=xdm post_id=324319 time=1657965738]
[quote=NorbVor post_id=324316 time=1657954885]
This is not first quarter, but last quarter phase.
[/quote]

This is first quarter, but a mirror image of first quarter.
[/quote]

This confused me as well. It would have been helpful to explain in the description that this is a mirror image.

[quote=xdm post_id=324319 time=1657965738]
Why present a mirror image, by the way :?:
[/quote]

Artistic license?

Thanks for putting the moon craters in temporal perspective.

[quote=Locutus76 post_id=324320 time=1657966388 user_id=144427]
[quote=wolfie138 post_id=324317 time=1657960197 user_id=126654]
WHy is the Moon so cratered and the Earth isn't?
[/quote]

Several reasons: First, the Earth has an atmosphere that helps burn up most of the smaller meteors (shooting stars). Second, the Earth is geologically active. Continents move and shift, volcanoes form new land and cover existing land with lava. Third, erosion by wind and water. These erode away any meteors that hit the ground over millions of years. As the surface of the Earth is 70% covered in water, not many meteors hit land anyway. So only the younger craters can still be found sometimes
[/quote]

Also, there is a good deal of evidence to suggest that the overwhelming majority of the cratering occurred over a relatively short period very early in the formation of the Solar System. The Late Heavy Bombardment is theorized to have occurred about 4 billion years ago, when the Earth's crust was just becoming solid and volcanic resurfacing was much more active than today. The Moon preserves this cratering, which is long since erased on the Earth.

[quote=wolfie138 post_id=324317 time=1657960197 user_id=126654]
WHy is the Moon so cratered and the Earth isn't?
[/quote]

Several reasons: First, the Earth has an atmosphere that helps burn up most of the smaller meteors (shooting stars). Second, the Earth is geologically active. Continents move and shift, volcanoes form new land and cover existing land with lava. Third, erosion by wind and water. These erode away any meteors that hit the ground over millions of years. As the surface of the Earth is 70% covered in water, not many meteors hit land anyway. So only the younger craters can still be found sometimes

[quote=NorbVor post_id=324316 time=1657954885]
This is not first quarter, but last quarter phase.
[/quote]

This is first quarter, but a mirror image of first quarter.
Why present a mirror image, by the way :?:

WHy is the Moon so cratered and the Earth isn't?

This is not first quarter, but last quarter phase.

[url=https://apod.nasa.gov/apod/ap220716.html] [img]https://apod.nasa.gov/apod/calendar/S_220716.jpg[/img] [size=150]Tycho and Clavius at Dawn[/size][/url]

[b] Explanation: [/b] South is up in this dramatic telescopic view of the [url=https://earthsky.org/astronomy-essentials/definition-moon-planet-terminator-line-twilight-zone/]lunar terminator[/url] and the Moon's rugged southern highlands. The lunar landscape was captured on July 7 with the moon at its [url=https://svs.gsfc.nasa.gov/4955]first quarter phase[/url]. The Sun shines at a low angle from the right as dawn comes to the region's young and old craters [url=https://apod.nasa.gov/apod/ap210805.html]Tycho and Clavius[/url]. About 100 million years young, [url=http://lroc.sese.asu.edu/exhibits/A%20New%20Moon%20Rises/38]Tycho is[/url] the sharp-walled 85 kilometer diameter crater below and left of center. Its 2 kilometer tall central peak and far crater wall reflect bright sunlight, Its smooth floor lies in dark shadow. Debris ejected during the impact that created Tycho make it the [url=https://skyandtelescope.org/observing/full-moon-is-tycho-time/]stand out[/url] lunar crater when the [url=https://apod.nasa.gov/apod/ap220715.html]Moon is near full[/url] though. They produce a highly visible radiating system of light streaks or rays that extend across much of the lunar near side. In fact, some of the material collected at the Apollo 17 landing site, about 2,000 kilometers away, likely originated [url=https://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20100114-tycho.html]from the Tycho impact[/url]. One of the oldest and largest craters on the Moon's near side, 225 kilometer diameter [url=https://www.flickr.com/photos/136797589@N04/26945796059/]Clavius is due south[/url] (above) of Tycho. [url=https://en.wikipedia.org/wiki/Clavius_(crater)]Clavius crater's[/url] own ray system resulting from its original impact event would have faded long ago. The old crater's worn walls and smooth floor are now overlayed by newer smaller craters from impacts that occurred after Clavius was formed. Reaching above the older crater, tops of the newer crater walls reflect this dawn's early light to create narrow shining arcs within a shadowed Clavius.


[table][tr][td=left][url=https://asterisk.apod.com/discuss_apod.php?date=220715][b]<< Previous APOD[/b][/url][/td] [td=center][url=https://asterisk.apod.com/view_retro.php?date=0716][b]This Day in APOD[/b][/url][/td] [td=right][url=https://asterisk.apod.com/discuss_apod.php?date=220717][b]Next APOD >>[/b][/url][/td][/tr][/table]