BAN #72: Flowing craters, Greasy space, thumbs-up

Pic o’ the Letter

A cool or lovely or mind-bending astronomical image/video with a short description so you can grok it

I know I’ve been writing about craters a lot on the blog, like this one about a flattened crater on Mars and another on a cool lunar crater (and I have notes for another about how crater rays form, too), but I couldn’t pass this up: The Lunar Reconnaissance Orbiter took a super-cool shot of a pair of craters that I really wanted to show y’all:

[Credit: NASA/GSFC/Arizona State University]

Usually the LRO camera points straight down (what is called nadir pointing) but sometimes it can be aimed more toward the lunar horizon providing an interesting oblique view. This shot shows the craters Korolov X (27 km wide, left) and Z (18 km wide, on the right but cut off). As I’ve written before, big craters get proper names, and little craters nearby get the same name with letters after them (Korolev itself is a huge 420 km-wide basin).

Korolev X is old and eroded, with soft features, while Z is clearly younger, with sharper brighter features, and also overlaps X a bit (which also proves it came later).

What’s really eye-catching is the dark stain in old X. That’s a flow of molten rock! I wasn’t sure at first how it formed, but the LRO page has a description that fits what you can see. It probably happened when Z formed; the impact created immense pressure that compressed the surface and formed the bowl-shaped depression and the rim wall. Molten rock pooled at the bottom for a very brief time (seconds?) but then the floor of X bounced back up once the pressure was gone, and the lava surged over the rim wall and into Z.

So cool. And on that page there’s also an anaglyph, a red/blue pair of images taken from slightly different angles, so if you have red/blue glasses, it mimics seeing it in 3D (glasses like that can be found very cheaply online; I get a pair for a buck). The rubble around Z where the rim collapsed is pretty impressive.

And you should subscribe to the LRO images page, where they put up lots of gorgeous lunar images like this. It’s definitely worth the time.

I learned a thing!

Wherein I learn a thing

Space isn’t empty. There’s a bunch of thinly distributed stuff out there between the stars, including gas — mostly hydrogen, but also helium, oxygen, and the other usual suspects — and a generic catch-all term we call “dust”. This can be tiny grains of silicates (basically like rock) as well as complex carbon molecules, sooty material called Polycyclic Aromatic Hydrocarbons.

The exact structure of the carbon dust isn’t well known. So some astronomers turned to the lab, mimicking the conditions where dust is formed — the materials blown out into space by “carbon stars”, red giants with a lot of carbon in their atmospheres. They let the carbon plasma expand into a vacuum, then examined the results.

[A typical aliphatic molecule superposed on an image of the Milky Way. Credit: D. Young]

About half the carbon was in the aromatic form (where carbon atoms forms rings like benzene) but the other half or so was in another form, called aliphatic, with long chains of carbon atoms linked together. That’s neat! Aliphatic compounds are greasy to the touch… meaning that the galaxy is polluted with greasy, stinky molecules.

I knew about the PAHs (I’ve written about them many times; they emit light in the far infrared and make WISE and Spitzer images beautiful) but not aliphatic molecules. So I learned a thing!

Apropos of nothing

Not everything needs to be themed

Look, I know the holidays can be… trying. There’s work to get done before taking time off, and then there are the usual stresses of family, shopping, being inundated with smarmy music, shorter days if you’re in the northern hemisphere, and so on.

A little support can go a long way, right? So here you go.

Use this pic as needed. You can do this.

Et alia

You can email me at [email protected] (though replies can take a while), and all my social media outlets are gathered together at about.me. Also, if you don’t already, please subscribe to this newsletter! And feel free to tell a friend or nine, too. Thanks!