January 22, 2008

Mercury's Sholem Aleichem Crater, by Messenger

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

The other day I wrote about the sense of humor the astronomers at APOD have. Now it's time to show some of the recent photos taken by the MESSENGER spacecraft that flew by the planet Mercury last week. This particular photo was taken last Monday, January 14th. The caption for the photo reads in part:

This image ... was acquired on January 14, 2008, 18:10 UTC, when the spacecraft was about 18,000 kilometers (11,000 miles) from the surface of Mercury, about 55 minutes before MESSENGER’s closest approach to the planet.

The image shows a variety of surface textures, including smooth plains at the center of the image, many impact craters (some with central peaks), and rough material that appears to have been ejected from the large crater to the lower right. This large 200-kilometer-wide (about 120 miles) crater was seen in less detail by Mariner 10 more than three decades ago and was named Sholem Aleichem for the Yiddish writer. In this MESSENGER image, it can be seen that the plains deposits filling the crater’s interior have been deformed by linear ridges. The shadowed area on the right of the image is the day-night boundary, known as the terminator.

One interesting fact that APOD pointed out is that many of the craters on Mercury are shallower than comparable craters on the Moon, the reason being the higher gravitational pull on Mercury, which "helps flatten tall structures like high crater walls."

As for Sholem Aleichem: He was a Russian Jewish writer (1859-1916) whose stories about Tevye the Milkman became the basis for the musical and film "Fiddler on the Roof."

Cross-posted on my new blog, Ministry of Space Exploration.


DramaMama said...

Salam, JD. I have a question that my kid asked that I don't have an answer to. Because I don't want to risk falling off the pedestal that Sara has put me on, thought I should persevere and get an accurate answer to them, although I was tempted to make one up.

So, we were driving to someplace last Saturday morning and Sara (my 5-yr old) pointed to the sky and wondered why the moon was still up there when it's already daylight. What is that phenomenon called and why does it happen (because come to think of it, I have seen it happening quite a few times)?

Thanks & jazakallah!

JDsg said...

Wa 'alaikum salaam. If there's a technical name for observing celestial objects in the sky during daylight, I'm unaware of it; however, I think "daylight observing" is as good as any other term. :) Of course the sun and the moon are the most commonly seen celestial objects in daylight; however, other objects have been seen in daylight as well, such as the (very rare) supernova (when a star explodes) and the occasional comet. The planet Venus can also be seen occasionally in either the late afternoon or the early morning before the sun has set or after it has risen, respectively.