Dating Theophilus, Cyrillus, & Catharina

[jrkirkham]

I recently uploaded this picture of Theophilus, Cyrillus, and Catharina to my Facebook page with a challenge for my friends to tell me which crater was the youngest, oldest, and how they arrived at their answer. That led a a fun discussion of lunar geology.

Here are the stats for the picture:
Camera: Canon 80D / Telescope: C11 + 2.5x Powermate + 3x Barlow / ISO: 6400 / Exposure: single frame @ 1/40 sec.

[Gordon]

Congratulations Rob on having your image selected as todays TSS APOD!

app.php/article/6-29-2020-tss-astrophot ... of-the-day

[helicon]

Congrats Rob on winning today's APOD. Some great images there.

[Graeme1858]

Nice lunar image Rob.

I'm guessing, from the overlaps, Theophilus is the youngest, then Cyrillus and the oldest is Catharina with the most craters in it.

Congratulations on the APOD.

Regards

Graeme

[Makuser]

Hello Rob. I consulted my lunar guru's book, "The Modern Moon" by Charles Wood about Catharina, Cyrillus, and Theophillis. Although they are all about 100 km in diameter, Catharina appears to be the oldest. Elongated craters on it's northeastern rim are aligned with the Mare Imbrium basin and suggests that it is the oldest. I hope this helps Rob, and congratulations on having your excellent lunar image selected as the TSS APOD Award winner today.

[jrkirkham]

Thank you everyone.

My friends on Facebook noticed two age indicators and missed a third. They noticed the weathering and sharpness of the craters. They didn't know what kind of weathering there might be with no atmosphere on the moon, but it looked to them like there had been some weathering of some type. They also noticed that Theophilus took a chunk out of Cyrillus indicating that Cyrillus was already there when Theophilus was formed.

The third indicator they all missed. That was the meteor strikes. Assuming that there are no special force fields that protect portions of the lunar surface from impacts, and assuming that objects randomly bombard all of the lunar surface, it stands to reason that the surface should be somewhat equally marked up by impacts, unless all surfaces were not of similar ages. The floor of Theophilus is smoother than the floors of the other two craters, thus indicating it has not been there as long. The same goes for the rest of the surface. If the same logic holds up the smoother floor of Mare Nectaris to the right of the craters must be more recent than the meteor scarred highlands to the left.

Anyway, we had a lot of fun with the picture and everyone got to try on their sleuthing hats for the day.

[TheButcher]

Very Nice image Rob and Congrats on the APOD!

[Ylem]

Congratulations
Awesome capture