BAN #411: Happy equinox!, The Impermanence of Apollo boot prints

21 March 2022 Issue #411

March 21, 2022

Astro Tidbit

A brief synopsis of some interesting astronomy/science news

Happy March equinox! Some people call this the spring equinox, but that shows a distinct northern hemisphere bias, so I go with the more generic “March”. Astronomers call it the vernal equinox, and while “vernal” means “spring” it’s taken on a different meaning here; it’s a point on the sky where the celestial equator (Earth’s equator projected on the sky) intersects the ecliptic (the plane of Earth’s orbit on the sky). The Sun moves along the ecliptic over the year, the reflection of the Earth’s motion around it, and on the moment of the vernal equinox the center of the Sun is exactly on the line between the southern and northern hemispheres. In March the Sun moves into the northern hemisphere, and in September it moves into the southern one.

This might help:

There are a TON of facts about the equinoctes (the plural of equinox), but my favorite is that the time of day the Sun rises and sets changes the most rapidly right now. It’s a little confusing, but happily I explained it carefully and with examples on the blog for the September 2019 equinox.  Basically, if you check when the Sun sets tonight, and when it sets tomorrow night, the difference will be large, several minutes. Check it again in June and the difference will be small, just seconds.

Anyway, for you northerners, spring is starting or getting closer (for me in Colorado, we’re expecting snow, which is typical for this time of year). Enjoy the hopefully nice weather!

Blog Jam

[The first highly focused image from JWST, from Thursday’s article. Credit: NASA/STScI]

Random Thoughts

Stuff I think about in the shower, typically

Right before the 51st anniversary of the Apollo 11 Moon landing in July, 2020, I was listening in on a livestream done by my dear friends Scott Sigler (if his name is familiar this might be why, or maybe because he’s a NYT best-selling author) and A Kovacs which they call “Sigler in Place”. They were talking about the landing, and either Scott mentioned this, or someone in the chat did, but the question arose: Is Neil Armstrong’s first boot print still intact on the lunar surface?

Once Neil Armstrong and Buzz Aldrin had set the Lunar Module down on the surface, Armstrong left the lander and descended a ladder attached to one of the module’s legs. He dropped down onto the wide footpad, then carefully extended one leg and pushed his boot onto the surface. He did this to test the surface to make sure they would be able to walk on it and to just report what it was like back to Mission Control (go here and find the part that starts at 109:23:38).

That was the first time in history a human had stepped on another world.

The Moon has very little erosion (mostly through small micrometeorite impacts), so left alone that boot print might last a long, long time.

But I strongly suspect it’s gone already. In fact, I don’t think it lasted through that EVA (extravehicular activity).

Why? Both Armstrong and Aldrin left the lander to walk around the site, and they did a lot of that. That first boot print was right where they had to get off the lander and walk around. Unless they took special care, they would’ve walked on it, probably multiple times. That would’ve wiped it out.

[One of the last images taken on the Moon by Apollo 11 shows how much foot traffic there was. Credit: NASA]

Also, not long before they left the Moon to go back up into lunar orbit and meet up with Michael Collins on the Command Module, they tossed a lot of stuff overboard they didn’t need, and which would have been useless weight (they wanted to minimize mass to conserve fuel if they needed it). All that stuff went out the hatch, right near where Armstrong set his foot down the first time. So that might have erased or disturbed the boot print as well.

Weirdly, the actual launch back into space probably didn’t disturb it at all! The Lunar Module had two parts: The lower Descent Stage (with the rocket and the legs and such) and the upper Ascent Stage. To go back into orbit, the Ascent Stage separated from the Descent Stage and used its own rocket to get them back up the to waiting Command Module; the Descent Stage was dead weight at that point, so there was no reason to bring it back up, and it was left on the lunar surface. It’s still sitting on the Moon, in fact.

But that means the plume from the Ascent Stage hit the Descent Stage and not the lunar surface immediately around it, so it had minimal effect on the dust there.

[The Lunar Module with the stages labeled. That’s Buzz Aldrin in front of it. For more info, go to the Apollo Lunar Surface Journal page and find “AS11-40-5927”. Credit NASA]

Mind you, the photo you always see of a boot print on the Moon was not Armstrong’s First Small Step; it was actually made by Buzz Aldrin later. He did that to get a single, pristine print that he could photograph so that scientists back on Earth could use it to examine how the lunar regolith (the fine, powdery material made up of eroded rock) behaved; this was called the Bootprint Penetration Experiment. That’s the photo you always see, and was done far enough away from the activity that it may still lie undisturbed to this day. So we have that, at least.

It’s funny to me that I never thought of this before (though after writing the bulk of this article I did a search and found this has been discussed before, and some folks reached the same conclusion I did, more or less). I’ve read so much about that first step, and how it was done, but never thought about whether that print was still there. I can’t say for 100% sure it’s gone, but that’s the way I’d bet, and I’d wager decent money.

That’s kinda sad. But still, all those subsequent prints are still there. I hope that someday that becomes some sort of global park, a historical site that will remain preserved for future generations, assuming we’ll have those on the Moon.

And I know which way I’d bet on that.

Et alia

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