Whatever hit the Moon in March, it left a double crater

> Looking at the density of craters how can we exclude the possibility that one of the craters simply existed before the new one?

One thing to note is that the density of craters on the moon is a result of a relatively infrequent number of impacts over an astronomically long time. With no process by which impact craters are weathered (wind, seismic activity), craters remain essentially forever.

To this layman who knows very little about orbits and impact craters, that explanation makes a lot of sense.

But the professional software engineer in me knows that even people well skilled in adjacent fields dont understand the issues that makes things “obvious” in my own field.

I therefore don’t doubt that the experts who study space debris considered the obvious explanation and rejected it. Or concluded that it wasn’t as obvious as it may seem.

That they are willing to defer to the crater-formation expert shows an admirable humility and deference to someone who is far more likely to know.

It's highly unlikely they would remain that close unless they split apart very soon before impact. Solar radiation exerts a small force on any object in space that depends on the object's orientation, reflectivity, rotation, etc. This introduces a small variation in it's flight path that can add up to several kilometres of uncertainty in just a few weeks. So even objects with very close flight paths, but differences in structure and rotation, will diverge. Objects with low mass to surface area and an elongated shape, such as empty fuel tanks, are subject to particularly high uncertainty in their trajectory.

I love the machine-generated ones, where it'll say "1 kilogram, or 2.20462 lbs".

I could understand if they went to 59 feet. But yards are roughly the same as a meter. Why even bother?

The replies to this make me think I've found "my people". Can we form a group?

Why? Those are both close enough for the intended purpose. 20 yards would be too imprecise, and 19 yards 24 inches is too wordy...

I think it is implied in the article that only the motor is massive enough to excavate a crater. The similarity in size of the craters suggests they were created by objects of similar mass.

At least one early rocket design (Atlas) had fuel tanks so insubstantial that they had to be pressurized until they were loaded with fuel on the pad, and a loss of pressure could be expensive...

https://www.youtube.com/watch?v=imkdz63agHY

I don't think anything manmade and space-borne is going to have enough structural integrity to perform any kind of summersault upon impact at that velocity.

See the fighter jet vs concrete wall video [1]. That was going at 500mph, and notice how the tail of the craft doesn't even perceptibly slow down. And a change in velocity would be required for the tail to rotate around (whether the impact is on an angle or head on)

This space object was travelling at 5800mph, 11+ times the speed. Sure a meter or so of moon dust may be a bit softer, but its solid rock underneath right? I'd guess the equivalent would be putting a kitchen sponge between that fighter jet & concrete wall.

[1] https://www.youtube.com/watch?v=F4CX-9lkRMQ

From TFA, "No other rocket body lunar collision has ever created two craters to our knowledge."

> Empty end hits first

In reality, the motor end should hit first, since free-falling objects usually rotate in such a way that the heaviest part is positioned at the bottom. The atmosphere could influence and modify this behaviour on other celestial bodies, but the Moon does not have it.

Is that more plausible or probable than two small objects spread out very slightly in the tangent plane and also a bit in time? They say "the" object a lot but is that something we have the precision to know, i.e. that it was not two objects instead? What I really want to know is if static discharge of that magnitude is common? If so, that's kinda cool.

That other thing wouldn’t have enough energy to make a comparable crater

Most of the stuff that leaves a small crater on the moon would burn up in Earth's atmosphere long before it hits the ground.

Random Factoid: it's extremely rare but the reason why the moon appears the same size as the sun is that the sun is 400x wider than the moon, but also 400x farther from the earth than the moon is.

Our moon holds so many mysteries. Just the very fact that such a large object can be so close in proximity to us while also orbiting is mind boggling.

https://astronomy.com/magazine/ask-astro/2000/10/why-is-the-...

I have the same question, if anyone knows the answer it'd be awesome.

I mean, sure, simply by virtue of the moon's being there, it sort of fends some stuff off like a fence.

But beyond that, is its gravitational pull adequate to affect trajectories?

If so, wouldn't earth's trump it? (Although the inverse square here may play a big part, but that would also make me more inclined to disregard the moon's gravity pull as assisting in any protection it otherwise naturally affords.)

Edit: clarified (?) thought

That would be Jupiter and Saturn. For this instance, it’s other way around.

About as much as the percentage of the sky it covers, I assume?

LRO is that camera and that's what took the picture we have.

It's getting up there in years so we could probably build something better today but we haven't yet.

Material science is moot at astronomical impact forces.

A meteorite hitting sand will make the same impact as if it hit steel.

I mean it definitely cratered...

I was thinking it might have been GME or AMC.

Maybe I've been hanging out on /r/WSB too much.

Got you -- :high_five:

Although my 2¢: it was a good joke until the second paragraph. That killed it for me – if I'm fed the explanation there's no more fun in "getting" it.

You're in luck! The moon has a solid iron, nickel core[1].

[1]https://moon.nasa.gov/inside-and-out/what-is-inside-the-moon

Apart from the geometrical explanation linked in the other comment, there's an Anthropic Principle angle here too -- the fact that eclipses seemed so "perfect and meaningful" to our ancestors was probably a big factor in the development of mathematics and engineering as they tried to predict the eclipses. another similarly intelligent species on a planet without such "perfect" eclipses wouldnt be intrigued by them enough to try to explain their timing. The fact that planets with such perfect sun/moon relationships are "rare" could be one of the missing factors in the Drake Equation. [something similar was a plot point in the scifi book Dragon's Egg]

re: Moon eclipses the sun.

Answer in this very same thread https://news.ycombinator.com/item?id=31893908

> I am genuinely curious if the Moon is hollow or not and what could be inside it

I mean, I think if it was, that would have caused some prior comment (and alarm).

It's not hollow.

I suppose one difference is that the pieces from Perserverance were _supposed_ to land on Mars. Whereas this object ended up floating around uselessly, like so much other "space junk". And because they suspect it's origin as being China, it makes sense to write it that way. Chinese junk, American junk, Canadian junk, although even these could be softened by "Chinese space junk, American space junk"... I wonder though if it is also being used in a retro sci-fi manner, in that there are crafts called "junks", particularly in English, "Chinese junks". See https://en.wikipedia.org/wiki/Junk_(ship) and https://www.newworldencyclopedia.org/entry/Junk_(ship)#:~:te.... Thus it is a chance to use the term for a sailing craft in a new context - a Chinese junk, but in space!

'Chinese' here isn't referring to the race, but to the country. So you shouldn't read it as implying racism in any way. In American terminology "American" is not a race nor is "Chinese". If they said "Asian Junk" that'd be racism.

I also bumped on that line as it felt completely unnecessary.

That’s not my experience at all. Here’s some quotes from NASA indicating what you describe is not their attitude at all.

> Space junk is no one countries’ responsibility, but the responsibility of every spacefaring country.

> We have generated a global problem that can only be solved with the help from other Countries.

Both from https://www.nasa.gov/centers/hq/library/find/bibliographies/...

What makes you say this? It is supposed to be a spent stage of a Chinese rocket booster - though there is no confirmation yet and this is the prevailing theory.

Right now it is space junk hitting the moon and it would be space junk no matter the origin of the spent rocket booster.

Referring to a discarded booster as space junk is very much on-brand for The Register, irrespective of who launched it.

But we wouldn't know if it was a Chinese satellite that suffered from a catastrophic failure would we? The Chinese state provides very little information on its space program.

Agree. People, please go re-read Manufacturing Consent.